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A review of the factors affecting the costs of bovine mastitis : review article

A review of the factors affecting the costs of bovine mastitis : review article Review article — Oorsigartikel A review of the factors affecting the costs of bovine mastitis a* b b K R Petrovski , M Trajcev and G Buneski THE COST OF MASTITIS TO THE ABSTRACT DAIRY INDUSTRY Mastitis is one of the most prevalent production diseases affecting the dairy cattle industry There have been many articles pub- worldwide. Its occurrence is associated with direct and indirect losses and expenditures. lished worldwide on the economics of When estimating the cost of mastitis to the dairy industry the cost of the control mastitis. When considering the cost of programmes must be added. The direct losses of mastitis are the only costs obvious to the any disease, it must be remembered that farmer. The difference between the costs of mastitis on one side and the benefits of mastitis every disease has direct and indirect control on the other side will give us a picture of the economic efficacy of the mastitis control costs. Bennett et al. estimated that the total programme. Continuing education of the farmer is needed for better mastitis control costs of each disease can be much higher programmes. This article is an attempt to review briefly all relevant factors included in the than the direct expenditure . Most of the economics of bovine mastitis and to illustrate the authors’ view of some of the costs. available estimates take into account only Key words: cost, dairy cattle, mastitis, mastitis control, milk production. a part of the real cost of mastitis, as esti- Petrovski K R, Trajcev M, Buneski G A review of the factors affecting the costs of bovine mating the true costs associated with mastitis. Journal of the South African Veterinary Association (2006) 77(2): 52–60 (En.). Institute of mastitis is notoriously difficult. It is even Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11 222, more difficult to quantify the losses asso- Palmerston North, New Zealand. ciated with sub-clinical mastitis, because they are not visible to farm owners. To avoid underestimating the consequences INTRODUCTION year of which a loss of £100/cow/year of mastitis in evaluations of economic-loss Mastitis is defined as an inflammation was due to sub-clinical mastitis alone in it is important to account for all of the cost of the mammary gland. It is a complex high Bulk Tank Somatic Cell Count factors involved. disease involving many factors, which is (BTSCC) herds . According to Ott the The estimation of the economic costs mainly caused by bacteria and there is no total production loss due to mastitis in the associated with mastitis depends on hav- simple model that encompasses all possi- USA is $108.00 per cow for herds with ing the following data: 25,64 ble facets . Despite intensive research average BTSCC of 200 000–399 999 cells/ 1. An estimate of the incidence and and the implementation of various masti- m and $295.24 per cow for herds with prevalence of mastitis in the popula- tis control strategies over the decades, average BTSCC 400 000 and above or tion is a prerequisite for the estimation bovine mastitis has not disappeared and losses of approximately $1 billion to the of its real cost to the dairy industry. the reduction in the prevalence of sub- USA dairy industry, based only on There is currently a general demand clinical mastitis has been minimal .On BTSCC, as measure of sub-clinical masti- for regular monitoring, recording and the other hand, there has been a consider- tis . research to establish the incidence able decrease in the incidence of clinical There is common confusion between and prevalence of mastitis. cases of mastitis worldwide as a result of the terms ‘loss’ and ‘cost’, so it is impor- 2. The severity of the physical effects of these control measures. tant first to clarify the terminology. In this mastitis on milk production, which Bovine mastitis is considered to be one article the following terms will be used as will depend on many factors, such as of the most economically important dis- defined: virulence of the mastitis-causing eases for the dairy industry in developed 1,11,16,23,25,27,33,46,60,64,66 a) Loss implies a benefit that is taken organisms, stage of lactation, age of countries . Morin et al., away (e.g. the production loss experi- the cow and udder defence mecha- monitored 4 Illinois herds for 12 months enced because contaminated milk nisms. and reported mastitis-associated eco- must be discarded); alternatively, it 3. Identification of the prevention and nomic losses ranging from US$161.79 to 52 represents a potential benefit that is treatment measures undertaken. It is $344.16 per lactating cow/year . The mag- not realised (such as an evident generally easy to calculate the expen nitude of the economic losses to the dairy 46,66 decrease in the milk yield) . diture on mastitis control. industry in the USA due to mastitis was b) Expenditures represent some eco- around $1.3 billion in 1979 and around 4. Valuation of the production losses, 48 15 nomic effects of disease that are mani- $2 billion in 1988 and 1993 (not factored - treatments and expenditures on pre fested as extra inputs into livestock for inflation). The total financial cost of - vention and control incurred. Produc production (such as treatment and mastitis to the average Scottish dairy herd tion losses caused by mastitis are 9,46,66 prevention of mastitis) . in 1996 was estimated to be £140/cow/ likely to be influenced by the age, c) Economic cost is the monetary value of breed and type of the cow, stage of Institute of Veterinary, Animal and Biomedical Sciences, all the economic effects, both losses lactation, milk yield before mastitis Massey University, Private Bag 11 222, Palmerston and expenditures, consequent upon North, New Zealand. occurred, milk price, premiums and 9,46,66 Faculty of Agr icultural Science and Food, Bul. the occurrence of disease . penalties, mastitis-causing organism, ‘Aleksandar Makedonski’ bb., 1000 Skopje, Macedonia. This article briefly reviews all the inflammation grade and distribution, *Author for correspondence. relevant factors influencing the economic diagnosis, treatment cost, prevention E-mail: [email protected] cost of bovine mastitis. Received: September 2005 . Accepted: May 2006. cost and analytical model. 52 0038-2809 Tydskr.S.Afr.vet.Ver. (2006) 77(2): 52–60 5. Other cost factors – e.g. farm manage- found that the addition of antimicrobials amount of time is used as real veterinary ment, culling, replacement and fatali- to supportive treatment is more effica- clinical work. The calculation of the esti- ties. cious and cost-effective than supportive mated cost of this element is from the Many techniques and methods have treatment alone, projected that cows invoices. The fees are usually charged at been used to estimate production losses without mastitis will produce 8265 kg of the farm level and if individual cow-cost from mastitis in dairy cattle. Methods milk (305-days in lactation) . Cows is required, then some modelling can be commonly used are: producer surveys, treated with supportive treatment only applied, or the amount on the invoices is regression analyses relating milk somatic produced 7838 (3.064–11.111) kg of milk, simply divided by the numbers of cows in cell counts, between-herd comparisons, while cows with added antimicrobials to the herd. between-cow yield comparisons, within- the treatment produced 7975 (5.002– udder yield comparisons, within-cow 11.163) kg, when discarded milk was Cost of the drugs yield comparison and studies between included . Assuming that none of the (Refs 1, 2, 10, 11, 14–16, 23, 28, 31, 38, 42, 43, 49, 52, 53) identical twins. De Graves and Fetrow unmarketable milk was fed to calves, the This part of the mastitis cost is easily stated that none of the techniques used cost of mastitis was 3 times higher in the calculated from the invoices of purchases are perfect, due to lack of direct measure group treated only with supportive treat- of drugs on the farm. A similar calculation of how much milk a cow would have pro- ment . may be done for the expenditure on the duced if there was no occurrence of masti- There are 2 elements of the treatment treatment of individual cases. tis during lactation, and they all have a cost: veterinarians’ fees and the cost of degree of inherent bias, which, in most drugs. In addition to the financial consid- Discarded milk cases, tends to underestimate the actual erations, the treatment of cows with clini- (Refs 1, 6, 11, 14–16 , 23–25, 31, 36, 38, 39, 42, 43, 52, 53, 66, 67, 74, 78) milk yield decrease that has occurred . cal mastitis is disruptive to the normal 25,31 The assessment of the cost of discarded milking routine . The economics of mastitis needs to be milk should include the milk withdrawn addressed at the farm or herd level and during and after the treatment, which depends on local, regional, epidemiologi- Veterinary time and consultation fees (Refs 1, 6, 11, 14–16, 23, 25, 28, 31, 36, 38, 43, 49, 52, 53, 67) depends on the withholding periods of cal, managerial and economic conditions. the drugs used and current regulations. The veterinary time and consultation At the herd level, as stated by Seegers The cost of discarded milk is usually fees can vary considerably in a mastitis et al., some compensation or buffer mech- estimated easily. In cases where mastitic control programme. These services are anisms can act and this should be taken milk is used for calf-rearing, estimation of charged on an hourly basis, per-cow-per- into consideration in the estimates. An the cost of mastitis should be carefully year basis, or other methods. They can be example is a farmer who decides to cull assessed. The system for accounting for applied to the individual cow, a group of cows with high somatic cell count (SCC), the economic costs associated with cows or a whole herd. based on the BTSCC and the milk pricing ‘discarded milk’ should be transparent. Veterinary time for the treatment of system, rather than on the absolute values No matter where it ends up the milk is not individual cows with clinical mastitis of the individual SCC results of the cows. sold, so it is a loss of income. A possible usually involves a minimal level of herd- Another example is a farmer who decides solution is to budget for the economic level consultancy and the cost per cow to cull an extra cow to decrease the BTSCC costs of mastitis to be debited with the full can be calculated from the invoices. The and give up selling a heifer . costs of the milk not sold and the calf rear- cost at the farm level may depend on the ing budget to be credited with the value of number of visits by the veterinarian. For LOSSES CAUSED BY MASTITIS the milk as a replacement for alternative example, in the Nordic countries all mas- sources of feed. If the estimates of milk titis cases are attended by a veterinarian. Direct losses due to mastitis losses are calculated on basis of BTSCC, In most other countries, such as South Direct costs of mastitis to the dairy then discarded milk in many cases is not Africa, USA, Australia and New Zealand, industry include the costs of treatment taken into account, leading to underesti- the veterinarians attend only some cases (veterinarian’s time and drugs), dis- mates of real mastitis costs . In many of mastitis. In such situations, the calcula- carded milk (during both the course of dairy countries it is common practice for tion of costs on a per cow basis, from data treatment and withholding periods) the farm owners of herds with average collected at the farm level, needs some herdsman’s time, fatalities and the costs high BTSCC to withhold or discard the modelling. associated with repeated cases of mastitis. milk from the cows with highest SCC, Group level service includes treatment In many cases direct losses are the only aiming to control their bulk milk in and prevention of mastitis in a specific cost of mastitis realised by the farmers. acceptable levels. group, such as age-categories, heifers or newly purchased cows. In this case, part Treatment cost of the veterinary time is clinical work, and Labour cost (Refs 6, 10, 11, 16, 23–25, 31, 36, 38, 39, 41–43, 48, 49, 60, 66, 67, 74) usually there will be some consultancy There appear to be 2 main approaches The cost of treatment of clinical cases is time as well. Calculation of the estimated in the literature for dealing with the an important element in the expenditure cost per cow in such a case is difficult, as it expenditure on labour for mastitis treat- on mastitis. Very commonly, the size of is unknown how much consultancy time ment. The 1st one is to consider the the veterinarians’ bills tends to be seen as has been spent per individual animal. The labour time as a direct cost of the disease ‘the cost of disease’ in the farmers’ eyes. In usual approach is to divide the amount and include it in the calculations as 1,11,15,16,36,38,42,43,46,49,52,53,66,78 fact, in general, the treatment of a disease on the invoice by the number of animals such . The 2nd such as mastitis, is only a small proportion attended. approach is to calculate the labour cost if a of the disease cost . farm specifically employs additional Most of the time when dealing with When estimating the treatment cost, the labour to manage treatment, segregation, herd problems is spent on consultancy 23–25 efficacy and cost-effectiveness should be or other aspects of mastitis control . work, for example dealing with high taken into account. For example, Shim The more usual case is that mastitis con- BTSCC herds or mycoplasma mastitis- et al. comparing 2 treatment protocols trol and treatment are handled by existing affected herds. In this case only a small 0038-2809 Jl S.Afr.vet.Ass. (2006) 77(2): 52–60 53 52 farm labour (i.e. no labour reduction accounts for the majority of economic affected by marked modifications in their would occur if mastitis cases were re- costs of mastitis. Education on this matter milk production curves and recovered in duced). In our opinion, the workers’ time is necessary because unrecognised indi- less than 5 weeks . It has been reported should be included in the calculations of rect losses can be a reason for difficult that the milk yields of older cows were mastitis cost. The estimation of the time implementation of mastitis control mea- obviously affected if mastitis occurred spent per case is variable and will depend sures, as farmers usually hold an opinion early in lactation, while younger cows’ on many factors, such as type of mastitis, that their own losses, due to mastitis, are yields are sensitive, with carry-over ef- milk yield, farm size, hired labour and much lower than the estimates provided fects seen if mastitis occurred after the 13 25,62 farm owner. For example, peracute cases for the industry by the experts . Indirect peak of lactation . Rajala-Schultz et al. of mastitis, associated with general ill- losses include the decreased milk produc- analysed records of over 24 000 Finnish ness, requires more time for treating, tion due to clinical or sub-clinical mastitis, Ayrshire cows, and reported that milk nursing and frequent stripping than mild decreased milk quality, increased culling, production declined 4 weeks before the subacute mastitis with only changes in loss of premiums, penalties, pre-term onset of clinical mastitis and dropped fur- the milk. drying-off, animal welfare aspects and ther below the curve of ‘healthy’ cows other associated health problems. during the 1st week afterwards. Milk yield never reached the pre-mastitis lev- Fatality (Refs 6, 15, 23, 33, 38, 39, 49, 52, 60, 66) els if mastitis occurred in early lactation Decrease in milk yield Severe cases of mastitis can lead to the (before peak) . A decreased milk produc- (Refs 1, 3, 6, 11, 14–16, 23–25, 28, 31, 33, 36, 38, 39, 41, 43, 46, 48, 49, 52, 54, 60, 66, 71, 74) death or euthanasia of the affected cow. tion before the occurrence of clinical mas- The main factor in causing economic The cost of a fatality is greater than simply titis was presumably due to the effects of losses due to both clinical and sub-clinical the value of the cow in the market, as it in- sub-clinical infection. mastitis is a more or less persistent cludes the lost margin from the incom- A higher level in milk yield prior to decrease in milk yield. Usually there will plete portion of its lactation. According to mastitis could be expected to be associ- be a short-term depression in yield of Kossaibati and Esslemont it also included ated with higher losses in milk (both in 33,42 variable severity and, in case of no micro- the cost of a replacement heifer . Mortal- absolute value and in percentage) bial cure and recovery, a longer lasting ity rate for clinical mastitis is usually low. The pathogenesis of mastitis, in many effect, sometimes carrying over into the Wilesmith et al. reported between 0.3 and cases, includes damage to secretory tissue next lactation/s. Milk production losses 0.6 % of mastitis cases to be fatal . World- and its replacement with fibrous tissue are typically estimated to account for 70 to wide, higher mortality rates caused by leading to a permanent decrease in milk 80 % of all mastitis losses in a typical mastitis are seen in specific situations yield from the affected quarter . In addi- 16,25,27,38,41,52,64 herd . with a high prevalence of Gram-negative tion, it is probable that part of the decrease infections, particularly coliform mastitis. Losses in milk yield (not including of the milk production is due to an Menzies et al. recorded a fatality rate of discarded milk) need to be assessed increased demand for energy by the 14 % and a further 21 % early culling within several time-frames. There are the immune system, a decreased appetite because of the condition in a study short-term effects on the current lactation associated with the inflammatory process involving 264 cases of acute and peracute and long-term effects, including carry- and lowered feed intake due to pain and toxic mastitis in Northern Ireland .By over effects into the next lactation or decreased mobility. contrast, Bradley and Green reported a beyond, that are usually estimated using Some mastitis-causing organisms were mortailty rate of 0.6 %, in general, and several types of comparison or modelling shown to have a more profound impact 33,66 16,25,77 2.2 % due to Gram-negative organisms in approaches . on milk yields than others . Mastitis 6 Somerset dairy herds . Estimates of milk yield loss are still cases caused by Staphylococcus aureus gen- under debate and likely to be influenced erally evolve into persistent but moderate Repeated cases of mastitis by the age, breed and type of cow, mor- infections, unlike mastitis caused by Some dairy cows suffer repeatedly from phological characteristics of the udder, coliforms. Thus, the mastitis-causing mastitis during a single lactation. stage of lactation, pregnancy status, milk organism may contribute to the residual Kossaibati and Esslemont found that a yield before mastitis occurred, masti- variation of responses, as well as to the typically affected cow suffers on average tis-causing organism, inflammation level of intensity. Generally it is estimated 1.6 cases per lactation . The extra costs of grade, duration and distribution, diagno- that the greater the inflammation the less that 0.6 repeat case should be taken into sis (early or late after the occurrence), milk is produced. account when assessing losses caused by treatment, feeding practices, season, There are 3 broad groups of comparison mastitis. For these repeated cases only the recurrence of mastitis during the same or models: (1) between herd comparison, (2) relevant direct costs should be included previous lactation, comparison model between-cow or within-herd compari- (i.e. cost of drugs, herdsman’s and/or (what is the control group) and the ana- son, and (3) between-quarter or within- veterinarian’s time and discarded milk). lytical model. udder comparison. A comparison of the For the indirect costs, it is important to It is generally accepted that mastitis relative yields of herds with varying calculate only additional losses associated occurring earlier in lactation will lead to levels of mastitis may be used to estimate with further decrease in milk yield and greater milk yield losses. Lescourret and the decrease in milk production. How- increased risk of culling. The rest of the Coulon reported that milk production ever, in this type of study, factors other indirect costs usually have been already curves of about one-third of the cows than mastitis may significantly contribute taken into account. infected early in lactation were little to any difference in milk yield that may be affected and yield recovered in less than 5 observed. The herds included in the Indirect losses due to mastitis weeks. The production curves of the rest study must be closely matched for factors Indirect losses due to mastitis, particu- of the infected cows were markedly such as location, breed, age, and plane of larly the subclinical form, are not well- - affected or the cows were culled. By con nutrition. The between-cow comparison recognised by many farmers. It is gener- trast, more than half of the cows infected model is also affected by some non- ally accepted that subclinical mastitis from mid- to late-lactation were not mastitis compounding factors such as age 54 0038-2809 Tydskr.S.Afr.vet.Ver. (2006) 77(2): 52–60 3,8,16,22,24,25,43,50,54,75 and breed and the cows must be closely tion compared with mastitis in mid to late yield and economic losses . matched for such factors. Within-udder lactation. Losses from 0 to 200 kg/cow/ There is considerable variation in the esti- yield comparisons compare a masti- month were estimated by Hortet and mates of the cost of milk loss in studies tis-infected quarter with an opposing Seegers in cases of clinical mastitis occur- that have related milk yield to SCC. Thus, mastitis-free quarter. Generally it is ring before the expected peak of the lactation losses of 80 kg and 120 kg accepted that the contra-lateral quarters lactation or 0 to 100 kg/cow/month by primiparous and multiparous cows, of the udder, when both are un-infected, with occurrences in mid- to late-lacta- respectively for each 2-fold increase in the give approximately the same volume of tion . Houben et al., using records for geometric mean of SCC above 50 000 was milk. However, while within-udder over 5300 lactations of nearly 2500 black estimated by a regression analysis of data comparison avoids sources of variation and white cows in Denmark, with from 19 papers . Similarly, Bennedsgaard which may confound other estimates of approximate calculated production of et al., analysing data from 17 500 lactations decreased milk production, it is possible 7500 kg, reported the estimated effect of in 48 Danish organic herds, reported that within the infected cow, un-infected clinical mastitis on production of 527 kg of average losses of 0.2, 0.3 and 0.4 kg of quarters partially compensate by produc- milk for ≥3 cases of clinical quarters in the energy-corrected milk/day in the 1st, 2nd ing more milk or both produce less as the 2nd lactation . Rajala-Schultz and Grohn and 3rd or later lactations, respectively, cow is sick. There is evidence that masti- recorded, in cows of 2nd parity, mean milk with each 2-fold increase in SCC between tis-free quarters may compensate for loss of 294, 348 and 110 kg milk if mastitis 100 000 and 1500 000 cells/m . Losinger quarters with mastitis by increasing milk occurred before peak, between peak and estimated loss of US$810 ± 480 million to 30,31,45 production . If compensation does in 120 days and later in lactation, respec- the USA economy as a whole caused by fact occur, then this would cause overesti- tively . The losses in older cows were sig- reduced milk production associated with mation of the actual milk loss as a result of nificantly higher. For example, spanning an increase in BTCSS during 1996 . 16,30 mastitis . Hortet and Seegers, using a 3 lactations in cows, mean recorded loss regression-modelling approach to ana- was 555, 329 and 357 kg, respectively . Milk quality changes lyse data from 20 papers published world- The economic losses that should be wide, predicted the average milk-yield Long-term effects included in the calculations due to milk loss over the lactation was 300–400 kg (i.e. This is an area that needs more attention quality changes are poorer milk composi- 4–6 %) per treated case of clinical mastitis from research, although available esti- tion, zoonotic risk and hygienic milk qual- in a Holstein Friesian cow producing mates generally indicate there are both ity changes leading to public health approximately 7000 kg/lactation. In long-term decreases in milk production considerations, lower end-product yields primiparous cows, the average loss was after episodes of clinical mastitis and and quality, shorter shelf-life of the final lower (200–300 kg) and mild patterns of long-term economic losses associated products and a decrease in profitability to 24,25,42,62,71 mastitis were more frequent than in with chronic mastitis . both producers and processors. multiparous ones. Cases occurring before Deluycker considered that the cows the peak of lactation were associated with affected by clinical mastitis in the 1st lacta- Compositional changes (Refs 1, 6, 14, 16, 31, 33, 36, 46, 52, 60, 66, 71, 74, 75, 78) higher average losses (450–550 kg) than tion but not in the next do not have a cases occurring later. Similarly Seegers higher, or compensatory increase in milk Mastitis is responsible for a number of et al. estimated loss of about 375 kg (5 %) yield when compared with cows free of changes in milk composition. While the per average clinical case, occuring in the mastitis in 2 successive lactations, even if effects of mastitis on the concentrations of 2nd month of lactation in a Holstein the infection was eliminated . Fetrow protein and fat in the milk are variable, cow . et al. found that the carry-over effect of changes in the actual composition of The estimates need to be used with mastitis and high SCC from one lactation these components, especially protein, caution, especially for breeds other than to the next was generally statistically are more consistent and often quite 16,36,66 Holstein Friesian or if unusual mastitis- significant but small, amounting to less marked . There is a reduction in the causing organisms are involved in clini- than a half of the effects of high SCC in the synthesis of the main components of cal-mastitis cases . current lactation. When production mea- milk, namely fat, lactose and protein, sures were adjusted for herd effect (roll- which may lead to a change in the relative ing herd average), the carry-over effect proportions of these components in the Short-term effects (Refs 6, 25, 33, 34, 62) was less than 20 % of the direct effect of milk. There are also increased concentra- For the estimation of short-term effects, increased SCC . However, chronic masti- tions of blood serum components due to it is necessary to bear in mind that an tis in 3 or more quarters is associated with the inflammatory reaction, e.g. proteins, infection can start and the milk yield can long-term economic losses in the follow- (serum albumin and immunoglobulins), 6,16,33 be reduced before the mastitis is detected. ing lactation of more than 350 kg in the chloride and sodium . These changes This may lead to underestimation of the 2nd and 3rd lactation and up to 381 kg of have direct and indirect effects on the real loss from mastitis . milk, up to and including 8 months into manufacturing properties of milk, often 34 1 75 Horter and Seegers, using regression the 2nd lactation . decreasing yield , quality and shelf-life 1,16,31,75 models, estimated that short-term losses of end-product . Furthermore, the from clinical cases of mastitis varied Elevated somatic cell counts – SCC presence of small quantities of antimicro- from 0 to about 3 kg/cow/day, but sug- The measurement of the SCC in bulk bials in the milk due to mastitis treatment gested that the estimates are lower than milk is the most universal method of eval- is associated with major losses incurred expected. They suggested that regression uating the occurrence of mastitis in dairy by the manufacturers when starter micro- models underestimate short-term losses, herds. There are significant correlations organisms are destroyed or their activity because of the difficulty in accounting for between the BTSCC of a farm and the eco- is slowed. variable losses occurring before a clinical nomic losses associated with decreased The final products, manufactured from diagnosis . milk production and quality. It is evident milk with changed composition, will Short-term reduction in milk yield is that an elevated SCC in milk, regardless of potentially command lower prices on the higher for clinical mastitis in early lacta- cause, is associated with decreased milk market and therefore will reduce the 0038-2809 Jl S.Afr.vet.Ass. (2006) 77(2): 52–60 55 income for the dairy industry and farm- fected cows adds to the total number of performance, economic factors, such as ers. The current milk-pricing system bacteria in bulk milk, regardless of degree milk price, the price of culled cows and 6,31,46,66 mainly relies on total-fat and total-protein of care taken with plant hygiene . the price, genetic merit and availability of yields. Since there is little financial incen- The stress to the farmer is considered as replacement heifers when determining tive for dairy farmers to do so, mastitis a potential public health concern. whether or not a cow should be culled. control programmes are not stimulated. The costs associated with the effects of The large effect of clinical mastitis before Also, due to the withdrawal period after mastitis on milk quality can be estimated peak lactation on short-term milk yield treatment of clinical cases, composition from the penalties imposed by the milk may partly explain the increased rate of changes in bulk milk can, as stated by processor for failure to meet the quality culling of cows infected early in lacta- 25,66 Seegers et al., be neglected in economic standards for SCC, microbial content and tion . When mastitis occures later than calculations . However, SCC and micro- antibiotic contamination. Some factors of 240 days after calving, the effect on bial count play an increasingly important concern for public health, such as expo- culling is not evident . This could be role in many payment systems and there- sure to potential pathogens and patho- explained by the fact that when the time fore a decrease in milk quality, due to gens resistant to antimicrobials in milk of next calving is approaching, farmers mastitis, plays a significant role. The that is used un-pasteurised, or the stress are prone to wait until the next time the introduction of premiums for milk quality to the farmer are not easily identified or cow calves and see whether she has stimulates interest on this matter (exam- costed. recovered from mastitis at the start of the ples seen in UK and Australia). The very next lactation . severe penalties for the presence of Culling and replacement cost As many of the factors of culling and antimicrobials in milk are a major incen- The term culling describes the re- replacement cost are not easily calculated, tive for ensuring that effective measures moval of an animal from a herd. A signifi- particularly the loss of genetic potential, it are in place on the farm to prevent con- cant part of the economic cost of mastitis will be necessary to employ complicated 1,6,10,11,14,16,23–25,28, tamination. is related to culling losses dynamic programming model to estimate 33,36,38,39,41,43,46,48,49,52,66,73–75,78 All costs associated with the compositio- of cows that have the cost of this group of factors. The cull- 1,3–5,16,33,41 nal changes, at farm level, can be calcu- or have had clinical mastitis or ing of an infected cow is likely to reduce 3,5,66 lated from the statements of milk collect- elevated SCC , and the increased ex- the risk of spread of infection through the ing and processing companies. When penditure associated with their replace- herd . The benefits of this effect should 1,6,11,15,31,36,41,46 the cost of mastitis is estimated on a per ment . Mastitis is usually be included in the dynamic programming cow basis, data collected at the farm second only to reproduction as the largest models. 4,10,16,27,39,45,66 level needs some modelling taking into involuntary culling category . account cow numbers and mastitis occur- Financial losses at the farm level can be Premium loss and penalties (Refs 1, 25, 66, 74, 78) rence. attributed to the loss of future income and 1,15,28,31 genetic potential resulting from cull- Penalties and premium losses in many Decreased hygienic quality of milk and ing. Schepers and Dijkhuizen stated that countries, particularly the European public health considerations the loss in this case is the difference Community and Australia, are an impor- When discussing the financial implica- between the income that a particular ani- tant part of the economic losses caused by tions of mastitis, its importance in public mal could earn during her remaining mastitis. The stringent standards for a health and the effects of mastitis on expected life and the expected average number of quality parameters including the consumers should not be over- income from replacement animals with contamination with antimicrobial sub- 1,16,31,46 looked . The risk of zoonotic diseases normal productive qualities and normal stances, microbes, flavour defects, and is also an important issue. This risk, how- probabilities of disposal over the same concentration of milk components as well ever, is not necessarily associated with period of time . However, the loss occurs as somatic cells count are monitored and mastitis. The potential spread of zoonotic only when animals have to be replaced penalised or compensated for in different organisms via milk, though rare in the before reaching their optimal economic countries. Morin et al. reported 21–40 % of era of pasteurisation, remains a risk age for culling. the cost of mastitis in 4 Illinois herds especially in the niche markets of un- The decision to cull is a complex one. accounted for milk quality premium pasteurised dairy products, and during There are different ways of classifying losses . pasteurisation failures . A number of culling according to the motives that lead All costs associated with premiums loss mastitis-causing bacteria and fungi are to the culling decision. The traditional and incurred penalties at the farm level potentially pathogenic to humans, caus- concept distinguishes between voluntary are easily calculated from the statements ing in many cases severe or even fatal and involuntary culling . A different of the milk collecting and processing com- infections or intoxications (e.g. staphylo- approach has gained attention that de- panies. To estimate the cost at cow level, coccal food poisoning with the thermo- fines biologic and economic culls which calculations from the data collected at the stable toxins produced by the staphylo- allows consideration of all the factors that farm level will need modelling, taking coccae; Strep. agalactiae human septicae- influence the decision-making process . into account cow numbers and mastitis mia and neonatal meningitis etc.) . The Lehenbauer and Oltjen stated that the occurrence. In the final model estimating extensive use of antimicrobials in the culling strategies are further influenced costs of premium losses and incurred treatment and control of mastitis has pos- by short-term fluctuations in cow num- penalties the labour ’s error should be sible implications for human health bers as well as by planned herd expan- taken into account, as this will lead to through an increased risk of antimicrobial sion . However, most cows are likely to be overestimates of the cost of mastitis; for resistant strains of microbes emerging removed from dairy herds only after they example, milking of a cow before with- 1,6,60 that may then enter the food chain or have displayed several reasons that holding period is finished, etc. through the increased risk of allergic reac- would lead to culling. Farmers may con- tions. sider many cow-related factors, such as Pre-term drying off The excretion of large numbers of masti- age, stage of lactation, milk production, In many cases, particularly from mid- tis-causing organisms in milk from in- health status, disposition, reproductive lactation onward, and when there is a 56 0038-2809 Tydskr.S.Afr.vet.Ver. (2006) 77(2): 52–60 re-occurring case, pre-term drying off the directly from invoices or calculated The costs associated with education of affected quarter of a cow is advocated. To according to standard treatment and the farmers and the labour can be par- avoid underestimates of mastitis conse- prevention costs, and from labour time tially estimated from the invoices for quences all those cases should be specifi- attended courses. Time spent on educa- for monitoring, treatment, preven- 16,36,66 cally recorded and accounted for in tion is difficult to estimate. Also decreased tion , and other expenditures. 33,78 economic-loss cost evaluations . SCC were associated with the higher Expenditure on mastitis control is deter- education qualifications of the farmers or mined by which control methods are workers and not necessarily related to employed, namely: educational costs, Animal welfare aspect of mastitis knowledge about mastitis, so to try and pre-milking preparation of the udders, The welfare implications of peracute attribute this to the cost of mastitis seems teat disinfection, dry-cow therapy and toxic mastitis are obvious. Allore and somehow unrealistic. mastitis vaccines, monitoring measures, Erband Payorala stated that more recent and maintenance of the milking machine. researchers have demonstrated signifi- Pre-milking preparations of the udders On the other hand, some authors also cant secondary hyperalgesia in cows 27,52 (Refs 16, 27, 52, 66) include the treatment of clinical cases , following mild clinical episodes of masti- 1,60 The costs of this procedure include the the pre-partum treatment of heifers , tis . It has been now accepted that masti- 27,52 time the milker takes for pre-stripping, culling and the management changes tis is associated with hyperalgesia, 27,52,66 washing and drying the udders; use of in milking routine , such as milking particularly in acute and peracute cases . water and teat disinfectant for washing, infected cows last. For example, Oliver Allodynia has been demonstrated for and paper towels for drying the udders. et al. reported that pre-partum antibiotic approximately 5 and 40 days in the case of Pre-milking teat disinfection is a rela- treatment of heifers yielded net revenue mild and moderate cases of mastitis, tively new concept in mastitis control. respectively . Concentrations of brady- of around $200/heifer/year . Contagious The majority of authors conclude that this kinin, cortisol and other kinins change mastitis in the herd is associated with 21,68–70 procedure is generally effective and not during clinical mastitis . Therefore shedding of the mastitis-causing organ- 35,55,58 expensive . On the contrary, Ruegg supportive treatment of each case of isms during milking and the risk of and Dohoo reported that the reduced in- mastitis can be an issue in the near future, cross-infection to other cows in the 14,31,52,73,74 cidence of clinical cases of mastitis does leading to increased costs of mastitis. herd . In such cases the mastitis not justify the added expense incurred prevalence in the herd will change, and According to Milk Hygiene directive from pre-milking teat disinfection, with a consequently mastitis costs will be in- 92/46 EEC it is not allowed to deliver milk benefit to cost ratio of 0.37 . Further creased. A proper transition management from cows suffering from recognisable research is needed to evaluate the eco- with the added cost of feed additives, inflammation of the mammary gland . nomic impact of the procedure. minerals and vitamins in particular, play an important role in modern mastitis Associated health problems Post-milking teat disinfection control programmes. A relatively new Mastitis is commonly associated with (Refs 2, 6, 16, 23, 27, 46, 52, 66) area in mastitis control strategies is vacci- other health problems such as reproduc- When assessing the cost of teat disinfec- 25,39,46,65,74 nation against different mastitis-causing tive failure and loss of appe- tion there are 3 main elements that should 39,46,66 organisms, and some research on the tite . There will be some indirect costs be addressed, namely the cost of the teat benefits of this procedure is already avail- due to increased risk of these associated disinfectant, the installation and mainte- able. DeGraves and Fetrow estimated health problems. nance cost, and labour cost (if included as benefit of $57 per cow if the herd is vacci- Recently there has been a trend when a cost of mastitis). Gill et al. found that the nated, assuming that 1 % of the cows estimating mastitis costs to take into cost of teat disinfectants is quite variable would normally contract coliform masti- account less food consumed to produce and is influenced by the amount used per tis during the season . less milk; a factor that was not usually cow per year and the cost per litre .On 10,28 considered . However, trying to differ- top of this the cost of the emollient used entiate between loss due to inflammation Educational costs must be added. of the secretory tissue and that due to a Continuous education of farmers is a Farms that have equipment for back- decreased intake because the cow is not necessary tool in the battle against bovine flushing of the milking units should feeling well is an unrealistic sophistica- mastitis . Farmers need to be aware of include the cost of installation, mainte- tion. A healthy udder is more efficient at economic cost of mastitis in the herd and nance and any disinfectant used. converting nutrients into milk ,soto the cost benefits of a mastitis control estimate the real cost of mastitis regarding programme that will increase the farm’s Dry-cow treatment and mastitis vaccines feed intake will need a complicated net income. The cost of commercial dry-cow prod- modelling. The importance of education is demon- ucts (antimicrobials and teat sealants) is Schrick et al. reported that cows with strated by the survey conducted by Gill somewhat variable, being influenced by 6,16,23,27,46,52,66,78 clinical or sub-clinical mastitis before the et al. . They found that a regular visit by a the product used . The cost 1st service had increased days to 1st veterinarian or udder health specialist, will be influenced by the numbers of cows insemination, increased days open and more years of ownership or managing a treated at drying off if selective dry-cow increased service to conception . This farm, more education, and frequent at- therapy is used. If labour cost is consid- indicates that some of the losses from tendance at dairy extension seminars ered as an element of the mastitis cost, associated health problems can be calcu- were associated with lower SCC, while then it should be added to the calcula- lated using relatively simple model- the increase in the total number of people tions. ling.mm working on the dairy farm was associated The same procedure can be used for cal- with an increased SCC. By contrast, culation of the estimated cost of vaccines 1,16,60,66 Cost of mastitis control programmes Kuiper et al. found that the education fac- against mastitis or some of the other The costs of mastitis control include tors were not as important as premiums immuno-modulatory systems and their expenditures which can be measured and penalties applied for milk quality . application. 0038-2809 Jl S.Afr.vet.Ass. (2006) 77(2): 52–60 57 60 Monitoring measures resist disease . Nutritional relationships ACKNOWLEDGEMENTS (Ref. 23) to host defence mechanisms have led to The authors wish to thank Duncan Mac- the idea of increasing the resistance of kenzie, Colin Holmes, Tim Parkinson, SCC monitoring cost dairy cattle to mastitis through nutrition. Ross Woods and Joyce de Moulin for con- (Ref. 23) Not only gross malnutrition, but also structive comments on article. Comments The cost of herd testing is calculated merely suboptimal levels of any one from two anonymous reviewers are also easily from invoices. Herd testing is done micronutrient is sufficient to adversely greatly appreciated. by different companies around the world 29,37,59,72 affect mammary gland immunity . and these usually record the volume, pro- REFERENCES Mastitis control programmes should tein and fat content, and SCC in the milk 1. Allore H G, Erb H N 1998 Partial budget of ensure that proper levels of all macro- and from each individual cow. 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A review of the factors affecting the costs of bovine mastitis : review article

Petrovski, K.R.; Trajcev, M.; Buneski, G.
Journal of the South African Veterinary Association – Jun 7, 2006
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Abstract

Review article — Oorsigartikel A review of the factors affecting the costs of bovine mastitis a* b b K R Petrovski , M Trajcev and G Buneski THE COST OF MASTITIS TO THE ABSTRACT DAIRY INDUSTRY Mastitis is one of the most prevalent production diseases affecting the dairy cattle industry There have been many articles pub- worldwide. Its occurrence is associated with direct and indirect losses and expenditures. lished worldwide on the economics of When estimating the cost of mastitis to the dairy industry the cost of the control mastitis. When considering the cost of programmes must be added. The direct losses of mastitis are the only costs obvious to the any disease, it must be remembered that farmer. The difference between the costs of mastitis on one side and the benefits of mastitis every disease has direct and indirect control on the other side will give us a picture of the economic efficacy of the mastitis control costs. Bennett et al. estimated that the total programme. Continuing education of the farmer is needed for better mastitis control costs of each disease can be much higher programmes. This article is an attempt to review briefly all relevant factors included in the than the direct expenditure . Most of the economics of bovine mastitis and to illustrate the authors’ view of some of the costs. available estimates take into account only Key words: cost, dairy cattle, mastitis, mastitis control, milk production. a part of the real cost of mastitis, as esti- Petrovski K R, Trajcev M, Buneski G A review of the factors affecting the costs of bovine mating the true costs associated with mastitis. Journal of the South African Veterinary Association (2006) 77(2): 52–60 (En.). Institute of mastitis is notoriously difficult. It is even Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11 222, more difficult to quantify the losses asso- Palmerston North, New Zealand. ciated with sub-clinical mastitis, because they are not visible to farm owners. To avoid underestimating the consequences INTRODUCTION year of which a loss of £100/cow/year of mastitis in evaluations of economic-loss Mastitis is defined as an inflammation was due to sub-clinical mastitis alone in it is important to account for all of the cost of the mammary gland. It is a complex high Bulk Tank Somatic Cell Count factors involved. disease involving many factors, which is (BTSCC) herds . According to Ott the The estimation of the economic costs mainly caused by bacteria and there is no total production loss due to mastitis in the associated with mastitis depends on hav- simple model that encompasses all possi- USA is $108.00 per cow for herds with ing the following data: 25,64 ble facets . Despite intensive research average BTSCC of 200 000–399 999 cells/ 1. An estimate of the incidence and and the implementation of various masti- m and $295.24 per cow for herds with prevalence of mastitis in the popula- tis control strategies over the decades, average BTSCC 400 000 and above or tion is a prerequisite for the estimation bovine mastitis has not disappeared and losses of approximately $1 billion to the of its real cost to the dairy industry. the reduction in the prevalence of sub- USA dairy industry, based only on There is currently a general demand clinical mastitis has been minimal .On BTSCC, as measure of sub-clinical masti- for regular monitoring, recording and the other hand, there has been a consider- tis . research to establish the incidence able decrease in the incidence of clinical There is common confusion between and prevalence of mastitis. cases of mastitis worldwide as a result of the terms ‘loss’ and ‘cost’, so it is impor- 2. The severity of the physical effects of these control measures. tant first to clarify the terminology. In this mastitis on milk production, which Bovine mastitis is considered to be one article the following terms will be used as will depend on many factors, such as of the most economically important dis- defined: virulence of the mastitis-causing eases for the dairy industry in developed 1,11,16,23,25,27,33,46,60,64,66 a) Loss implies a benefit that is taken organisms, stage of lactation, age of countries . Morin et al., away (e.g. the production loss experi- the cow and udder defence mecha- monitored 4 Illinois herds for 12 months enced because contaminated milk nisms. and reported mastitis-associated eco- must be discarded); alternatively, it 3. Identification of the prevention and nomic losses ranging from US$161.79 to 52 represents a potential benefit that is treatment measures undertaken. It is $344.16 per lactating cow/year . The mag- not realised (such as an evident generally easy to calculate the expen nitude of the economic losses to the dairy 46,66 decrease in the milk yield) . diture on mastitis control. industry in the USA due to mastitis was b) Expenditures represent some eco- around $1.3 billion in 1979 and around 4. Valuation of the production losses, 48 15 nomic effects of disease that are mani- $2 billion in 1988 and 1993 (not factored - treatments and expenditures on pre fested as extra inputs into livestock for inflation). The total financial cost of - vention and control incurred. Produc production (such as treatment and mastitis to the average Scottish dairy herd tion losses caused by mastitis are 9,46,66 prevention of mastitis) . in 1996 was estimated to be £140/cow/ likely to be influenced by the age, c) Economic cost is the monetary value of breed and type of the cow, stage of Institute of Veterinary, Animal and Biomedical Sciences, all the economic effects, both losses lactation, milk yield before mastitis Massey University, Private Bag 11 222, Palmerston and expenditures, consequent upon North, New Zealand. occurred, milk price, premiums and 9,46,66 Faculty of Agr icultural Science and Food, Bul. the occurrence of disease . penalties, mastitis-causing organism, ‘Aleksandar Makedonski’ bb., 1000 Skopje, Macedonia. This article briefly reviews all the inflammation grade and distribution, *Author for correspondence. relevant factors influencing the economic diagnosis, treatment cost, prevention E-mail: [email protected] cost of bovine mastitis. Received: September 2005 . Accepted: May 2006. cost and analytical model. 52 0038-2809 Tydskr.S.Afr.vet.Ver. (2006) 77(2): 52–60 5. Other cost factors – e.g. farm manage- found that the addition of antimicrobials amount of time is used as real veterinary ment, culling, replacement and fatali- to supportive treatment is more effica- clinical work. The calculation of the esti- ties. cious and cost-effective than supportive mated cost of this element is from the Many techniques and methods have treatment alone, projected that cows invoices. The fees are usually charged at been used to estimate production losses without mastitis will produce 8265 kg of the farm level and if individual cow-cost from mastitis in dairy cattle. Methods milk (305-days in lactation) . Cows is required, then some modelling can be commonly used are: producer surveys, treated with supportive treatment only applied, or the amount on the invoices is regression analyses relating milk somatic produced 7838 (3.064–11.111) kg of milk, simply divided by the numbers of cows in cell counts, between-herd comparisons, while cows with added antimicrobials to the herd. between-cow yield comparisons, within- the treatment produced 7975 (5.002– udder yield comparisons, within-cow 11.163) kg, when discarded milk was Cost of the drugs yield comparison and studies between included . Assuming that none of the (Refs 1, 2, 10, 11, 14–16, 23, 28, 31, 38, 42, 43, 49, 52, 53) identical twins. De Graves and Fetrow unmarketable milk was fed to calves, the This part of the mastitis cost is easily stated that none of the techniques used cost of mastitis was 3 times higher in the calculated from the invoices of purchases are perfect, due to lack of direct measure group treated only with supportive treat- of drugs on the farm. A similar calculation of how much milk a cow would have pro- ment . may be done for the expenditure on the duced if there was no occurrence of masti- There are 2 elements of the treatment treatment of individual cases. tis during lactation, and they all have a cost: veterinarians’ fees and the cost of degree of inherent bias, which, in most drugs. In addition to the financial consid- Discarded milk cases, tends to underestimate the actual erations, the treatment of cows with clini- (Refs 1, 6, 11, 14–16 , 23–25, 31, 36, 38, 39, 42, 43, 52, 53, 66, 67, 74, 78) milk yield decrease that has occurred . cal mastitis is disruptive to the normal 25,31 The assessment of the cost of discarded milking routine . The economics of mastitis needs to be milk should include the milk withdrawn addressed at the farm or herd level and during and after the treatment, which depends on local, regional, epidemiologi- Veterinary time and consultation fees (Refs 1, 6, 11, 14–16, 23, 25, 28, 31, 36, 38, 43, 49, 52, 53, 67) depends on the withholding periods of cal, managerial and economic conditions. the drugs used and current regulations. The veterinary time and consultation At the herd level, as stated by Seegers The cost of discarded milk is usually fees can vary considerably in a mastitis et al., some compensation or buffer mech- estimated easily. In cases where mastitic control programme. These services are anisms can act and this should be taken milk is used for calf-rearing, estimation of charged on an hourly basis, per-cow-per- into consideration in the estimates. An the cost of mastitis should be carefully year basis, or other methods. They can be example is a farmer who decides to cull assessed. The system for accounting for applied to the individual cow, a group of cows with high somatic cell count (SCC), the economic costs associated with cows or a whole herd. based on the BTSCC and the milk pricing ‘discarded milk’ should be transparent. Veterinary time for the treatment of system, rather than on the absolute values No matter where it ends up the milk is not individual cows with clinical mastitis of the individual SCC results of the cows. sold, so it is a loss of income. A possible usually involves a minimal level of herd- Another example is a farmer who decides solution is to budget for the economic level consultancy and the cost per cow to cull an extra cow to decrease the BTSCC costs of mastitis to be debited with the full can be calculated from the invoices. The and give up selling a heifer . costs of the milk not sold and the calf rear- cost at the farm level may depend on the ing budget to be credited with the value of number of visits by the veterinarian. For LOSSES CAUSED BY MASTITIS the milk as a replacement for alternative example, in the Nordic countries all mas- sources of feed. If the estimates of milk titis cases are attended by a veterinarian. Direct losses due to mastitis losses are calculated on basis of BTSCC, In most other countries, such as South Direct costs of mastitis to the dairy then discarded milk in many cases is not Africa, USA, Australia and New Zealand, industry include the costs of treatment taken into account, leading to underesti- the veterinarians attend only some cases (veterinarian’s time and drugs), dis- mates of real mastitis costs . In many of mastitis. In such situations, the calcula- carded milk (during both the course of dairy countries it is common practice for tion of costs on a per cow basis, from data treatment and withholding periods) the farm owners of herds with average collected at the farm level, needs some herdsman’s time, fatalities and the costs high BTSCC to withhold or discard the modelling. associated with repeated cases of mastitis. milk from the cows with highest SCC, Group level service includes treatment In many cases direct losses are the only aiming to control their bulk milk in and prevention of mastitis in a specific cost of mastitis realised by the farmers. acceptable levels. group, such as age-categories, heifers or newly purchased cows. In this case, part Treatment cost of the veterinary time is clinical work, and Labour cost (Refs 6, 10, 11, 16, 23–25, 31, 36, 38, 39, 41–43, 48, 49, 60, 66, 67, 74) usually there will be some consultancy There appear to be 2 main approaches The cost of treatment of clinical cases is time as well. Calculation of the estimated in the literature for dealing with the an important element in the expenditure cost per cow in such a case is difficult, as it expenditure on labour for mastitis treat- on mastitis. Very commonly, the size of is unknown how much consultancy time ment. The 1st one is to consider the the veterinarians’ bills tends to be seen as has been spent per individual animal. The labour time as a direct cost of the disease ‘the cost of disease’ in the farmers’ eyes. In usual approach is to divide the amount and include it in the calculations as 1,11,15,16,36,38,42,43,46,49,52,53,66,78 fact, in general, the treatment of a disease on the invoice by the number of animals such . The 2nd such as mastitis, is only a small proportion attended. approach is to calculate the labour cost if a of the disease cost . farm specifically employs additional Most of the time when dealing with When estimating the treatment cost, the labour to manage treatment, segregation, herd problems is spent on consultancy 23–25 efficacy and cost-effectiveness should be or other aspects of mastitis control . work, for example dealing with high taken into account. For example, Shim The more usual case is that mastitis con- BTSCC herds or mycoplasma mastitis- et al. comparing 2 treatment protocols trol and treatment are handled by existing affected herds. In this case only a small 0038-2809 Jl S.Afr.vet.Ass. (2006) 77(2): 52–60 53 52 farm labour (i.e. no labour reduction accounts for the majority of economic affected by marked modifications in their would occur if mastitis cases were re- costs of mastitis. Education on this matter milk production curves and recovered in duced). In our opinion, the workers’ time is necessary because unrecognised indi- less than 5 weeks . It has been reported should be included in the calculations of rect losses can be a reason for difficult that the milk yields of older cows were mastitis cost. The estimation of the time implementation of mastitis control mea- obviously affected if mastitis occurred spent per case is variable and will depend sures, as farmers usually hold an opinion early in lactation, while younger cows’ on many factors, such as type of mastitis, that their own losses, due to mastitis, are yields are sensitive, with carry-over ef- milk yield, farm size, hired labour and much lower than the estimates provided fects seen if mastitis occurred after the 13 25,62 farm owner. For example, peracute cases for the industry by the experts . Indirect peak of lactation . Rajala-Schultz et al. of mastitis, associated with general ill- losses include the decreased milk produc- analysed records of over 24 000 Finnish ness, requires more time for treating, tion due to clinical or sub-clinical mastitis, Ayrshire cows, and reported that milk nursing and frequent stripping than mild decreased milk quality, increased culling, production declined 4 weeks before the subacute mastitis with only changes in loss of premiums, penalties, pre-term onset of clinical mastitis and dropped fur- the milk. drying-off, animal welfare aspects and ther below the curve of ‘healthy’ cows other associated health problems. during the 1st week afterwards. Milk yield never reached the pre-mastitis lev- Fatality (Refs 6, 15, 23, 33, 38, 39, 49, 52, 60, 66) els if mastitis occurred in early lactation Decrease in milk yield Severe cases of mastitis can lead to the (before peak) . A decreased milk produc- (Refs 1, 3, 6, 11, 14–16, 23–25, 28, 31, 33, 36, 38, 39, 41, 43, 46, 48, 49, 52, 54, 60, 66, 71, 74) death or euthanasia of the affected cow. tion before the occurrence of clinical mas- The main factor in causing economic The cost of a fatality is greater than simply titis was presumably due to the effects of losses due to both clinical and sub-clinical the value of the cow in the market, as it in- sub-clinical infection. mastitis is a more or less persistent cludes the lost margin from the incom- A higher level in milk yield prior to decrease in milk yield. Usually there will plete portion of its lactation. According to mastitis could be expected to be associ- be a short-term depression in yield of Kossaibati and Esslemont it also included ated with higher losses in milk (both in 33,42 variable severity and, in case of no micro- the cost of a replacement heifer . Mortal- absolute value and in percentage) bial cure and recovery, a longer lasting ity rate for clinical mastitis is usually low. The pathogenesis of mastitis, in many effect, sometimes carrying over into the Wilesmith et al. reported between 0.3 and cases, includes damage to secretory tissue next lactation/s. Milk production losses 0.6 % of mastitis cases to be fatal . World- and its replacement with fibrous tissue are typically estimated to account for 70 to wide, higher mortality rates caused by leading to a permanent decrease in milk 80 % of all mastitis losses in a typical mastitis are seen in specific situations yield from the affected quarter . In addi- 16,25,27,38,41,52,64 herd . with a high prevalence of Gram-negative tion, it is probable that part of the decrease infections, particularly coliform mastitis. Losses in milk yield (not including of the milk production is due to an Menzies et al. recorded a fatality rate of discarded milk) need to be assessed increased demand for energy by the 14 % and a further 21 % early culling within several time-frames. There are the immune system, a decreased appetite because of the condition in a study short-term effects on the current lactation associated with the inflammatory process involving 264 cases of acute and peracute and long-term effects, including carry- and lowered feed intake due to pain and toxic mastitis in Northern Ireland .By over effects into the next lactation or decreased mobility. contrast, Bradley and Green reported a beyond, that are usually estimated using Some mastitis-causing organisms were mortailty rate of 0.6 %, in general, and several types of comparison or modelling shown to have a more profound impact 33,66 16,25,77 2.2 % due to Gram-negative organisms in approaches . on milk yields than others . Mastitis 6 Somerset dairy herds . Estimates of milk yield loss are still cases caused by Staphylococcus aureus gen- under debate and likely to be influenced erally evolve into persistent but moderate Repeated cases of mastitis by the age, breed and type of cow, mor- infections, unlike mastitis caused by Some dairy cows suffer repeatedly from phological characteristics of the udder, coliforms. Thus, the mastitis-causing mastitis during a single lactation. stage of lactation, pregnancy status, milk organism may contribute to the residual Kossaibati and Esslemont found that a yield before mastitis occurred, masti- variation of responses, as well as to the typically affected cow suffers on average tis-causing organism, inflammation level of intensity. Generally it is estimated 1.6 cases per lactation . The extra costs of grade, duration and distribution, diagno- that the greater the inflammation the less that 0.6 repeat case should be taken into sis (early or late after the occurrence), milk is produced. account when assessing losses caused by treatment, feeding practices, season, There are 3 broad groups of comparison mastitis. For these repeated cases only the recurrence of mastitis during the same or models: (1) between herd comparison, (2) relevant direct costs should be included previous lactation, comparison model between-cow or within-herd compari- (i.e. cost of drugs, herdsman’s and/or (what is the control group) and the ana- son, and (3) between-quarter or within- veterinarian’s time and discarded milk). lytical model. udder comparison. A comparison of the For the indirect costs, it is important to It is generally accepted that mastitis relative yields of herds with varying calculate only additional losses associated occurring earlier in lactation will lead to levels of mastitis may be used to estimate with further decrease in milk yield and greater milk yield losses. Lescourret and the decrease in milk production. How- increased risk of culling. The rest of the Coulon reported that milk production ever, in this type of study, factors other indirect costs usually have been already curves of about one-third of the cows than mastitis may significantly contribute taken into account. infected early in lactation were little to any difference in milk yield that may be affected and yield recovered in less than 5 observed. The herds included in the Indirect losses due to mastitis weeks. The production curves of the rest study must be closely matched for factors Indirect losses due to mastitis, particu- of the infected cows were markedly such as location, breed, age, and plane of larly the subclinical form, are not well- - affected or the cows were culled. By con nutrition. The between-cow comparison recognised by many farmers. It is gener- trast, more than half of the cows infected model is also affected by some non- ally accepted that subclinical mastitis from mid- to late-lactation were not mastitis compounding factors such as age 54 0038-2809 Tydskr.S.Afr.vet.Ver. (2006) 77(2): 52–60 3,8,16,22,24,25,43,50,54,75 and breed and the cows must be closely tion compared with mastitis in mid to late yield and economic losses . matched for such factors. Within-udder lactation. Losses from 0 to 200 kg/cow/ There is considerable variation in the esti- yield comparisons compare a masti- month were estimated by Hortet and mates of the cost of milk loss in studies tis-infected quarter with an opposing Seegers in cases of clinical mastitis occur- that have related milk yield to SCC. Thus, mastitis-free quarter. Generally it is ring before the expected peak of the lactation losses of 80 kg and 120 kg accepted that the contra-lateral quarters lactation or 0 to 100 kg/cow/month by primiparous and multiparous cows, of the udder, when both are un-infected, with occurrences in mid- to late-lacta- respectively for each 2-fold increase in the give approximately the same volume of tion . Houben et al., using records for geometric mean of SCC above 50 000 was milk. However, while within-udder over 5300 lactations of nearly 2500 black estimated by a regression analysis of data comparison avoids sources of variation and white cows in Denmark, with from 19 papers . Similarly, Bennedsgaard which may confound other estimates of approximate calculated production of et al., analysing data from 17 500 lactations decreased milk production, it is possible 7500 kg, reported the estimated effect of in 48 Danish organic herds, reported that within the infected cow, un-infected clinical mastitis on production of 527 kg of average losses of 0.2, 0.3 and 0.4 kg of quarters partially compensate by produc- milk for ≥3 cases of clinical quarters in the energy-corrected milk/day in the 1st, 2nd ing more milk or both produce less as the 2nd lactation . Rajala-Schultz and Grohn and 3rd or later lactations, respectively, cow is sick. There is evidence that masti- recorded, in cows of 2nd parity, mean milk with each 2-fold increase in SCC between tis-free quarters may compensate for loss of 294, 348 and 110 kg milk if mastitis 100 000 and 1500 000 cells/m . Losinger quarters with mastitis by increasing milk occurred before peak, between peak and estimated loss of US$810 ± 480 million to 30,31,45 production . If compensation does in 120 days and later in lactation, respec- the USA economy as a whole caused by fact occur, then this would cause overesti- tively . The losses in older cows were sig- reduced milk production associated with mation of the actual milk loss as a result of nificantly higher. For example, spanning an increase in BTCSS during 1996 . 16,30 mastitis . Hortet and Seegers, using a 3 lactations in cows, mean recorded loss regression-modelling approach to ana- was 555, 329 and 357 kg, respectively . Milk quality changes lyse data from 20 papers published world- The economic losses that should be wide, predicted the average milk-yield Long-term effects included in the calculations due to milk loss over the lactation was 300–400 kg (i.e. This is an area that needs more attention quality changes are poorer milk composi- 4–6 %) per treated case of clinical mastitis from research, although available esti- tion, zoonotic risk and hygienic milk qual- in a Holstein Friesian cow producing mates generally indicate there are both ity changes leading to public health approximately 7000 kg/lactation. In long-term decreases in milk production considerations, lower end-product yields primiparous cows, the average loss was after episodes of clinical mastitis and and quality, shorter shelf-life of the final lower (200–300 kg) and mild patterns of long-term economic losses associated products and a decrease in profitability to 24,25,42,62,71 mastitis were more frequent than in with chronic mastitis . both producers and processors. multiparous ones. Cases occurring before Deluycker considered that the cows the peak of lactation were associated with affected by clinical mastitis in the 1st lacta- Compositional changes (Refs 1, 6, 14, 16, 31, 33, 36, 46, 52, 60, 66, 71, 74, 75, 78) higher average losses (450–550 kg) than tion but not in the next do not have a cases occurring later. Similarly Seegers higher, or compensatory increase in milk Mastitis is responsible for a number of et al. estimated loss of about 375 kg (5 %) yield when compared with cows free of changes in milk composition. While the per average clinical case, occuring in the mastitis in 2 successive lactations, even if effects of mastitis on the concentrations of 2nd month of lactation in a Holstein the infection was eliminated . Fetrow protein and fat in the milk are variable, cow . et al. found that the carry-over effect of changes in the actual composition of The estimates need to be used with mastitis and high SCC from one lactation these components, especially protein, caution, especially for breeds other than to the next was generally statistically are more consistent and often quite 16,36,66 Holstein Friesian or if unusual mastitis- significant but small, amounting to less marked . There is a reduction in the causing organisms are involved in clini- than a half of the effects of high SCC in the synthesis of the main components of cal-mastitis cases . current lactation. When production mea- milk, namely fat, lactose and protein, sures were adjusted for herd effect (roll- which may lead to a change in the relative ing herd average), the carry-over effect proportions of these components in the Short-term effects (Refs 6, 25, 33, 34, 62) was less than 20 % of the direct effect of milk. There are also increased concentra- For the estimation of short-term effects, increased SCC . However, chronic masti- tions of blood serum components due to it is necessary to bear in mind that an tis in 3 or more quarters is associated with the inflammatory reaction, e.g. proteins, infection can start and the milk yield can long-term economic losses in the follow- (serum albumin and immunoglobulins), 6,16,33 be reduced before the mastitis is detected. ing lactation of more than 350 kg in the chloride and sodium . These changes This may lead to underestimation of the 2nd and 3rd lactation and up to 381 kg of have direct and indirect effects on the real loss from mastitis . milk, up to and including 8 months into manufacturing properties of milk, often 34 1 75 Horter and Seegers, using regression the 2nd lactation . decreasing yield , quality and shelf-life 1,16,31,75 models, estimated that short-term losses of end-product . Furthermore, the from clinical cases of mastitis varied Elevated somatic cell counts – SCC presence of small quantities of antimicro- from 0 to about 3 kg/cow/day, but sug- The measurement of the SCC in bulk bials in the milk due to mastitis treatment gested that the estimates are lower than milk is the most universal method of eval- is associated with major losses incurred expected. They suggested that regression uating the occurrence of mastitis in dairy by the manufacturers when starter micro- models underestimate short-term losses, herds. There are significant correlations organisms are destroyed or their activity because of the difficulty in accounting for between the BTSCC of a farm and the eco- is slowed. variable losses occurring before a clinical nomic losses associated with decreased The final products, manufactured from diagnosis . milk production and quality. It is evident milk with changed composition, will Short-term reduction in milk yield is that an elevated SCC in milk, regardless of potentially command lower prices on the higher for clinical mastitis in early lacta- cause, is associated with decreased milk market and therefore will reduce the 0038-2809 Jl S.Afr.vet.Ass. (2006) 77(2): 52–60 55 income for the dairy industry and farm- fected cows adds to the total number of performance, economic factors, such as ers. The current milk-pricing system bacteria in bulk milk, regardless of degree milk price, the price of culled cows and 6,31,46,66 mainly relies on total-fat and total-protein of care taken with plant hygiene . the price, genetic merit and availability of yields. Since there is little financial incen- The stress to the farmer is considered as replacement heifers when determining tive for dairy farmers to do so, mastitis a potential public health concern. whether or not a cow should be culled. control programmes are not stimulated. The costs associated with the effects of The large effect of clinical mastitis before Also, due to the withdrawal period after mastitis on milk quality can be estimated peak lactation on short-term milk yield treatment of clinical cases, composition from the penalties imposed by the milk may partly explain the increased rate of changes in bulk milk can, as stated by processor for failure to meet the quality culling of cows infected early in lacta- 25,66 Seegers et al., be neglected in economic standards for SCC, microbial content and tion . When mastitis occures later than calculations . However, SCC and micro- antibiotic contamination. Some factors of 240 days after calving, the effect on bial count play an increasingly important concern for public health, such as expo- culling is not evident . This could be role in many payment systems and there- sure to potential pathogens and patho- explained by the fact that when the time fore a decrease in milk quality, due to gens resistant to antimicrobials in milk of next calving is approaching, farmers mastitis, plays a significant role. The that is used un-pasteurised, or the stress are prone to wait until the next time the introduction of premiums for milk quality to the farmer are not easily identified or cow calves and see whether she has stimulates interest on this matter (exam- costed. recovered from mastitis at the start of the ples seen in UK and Australia). The very next lactation . severe penalties for the presence of Culling and replacement cost As many of the factors of culling and antimicrobials in milk are a major incen- The term culling describes the re- replacement cost are not easily calculated, tive for ensuring that effective measures moval of an animal from a herd. A signifi- particularly the loss of genetic potential, it are in place on the farm to prevent con- cant part of the economic cost of mastitis will be necessary to employ complicated 1,6,10,11,14,16,23–25,28, tamination. is related to culling losses dynamic programming model to estimate 33,36,38,39,41,43,46,48,49,52,66,73–75,78 All costs associated with the compositio- of cows that have the cost of this group of factors. The cull- 1,3–5,16,33,41 nal changes, at farm level, can be calcu- or have had clinical mastitis or ing of an infected cow is likely to reduce 3,5,66 lated from the statements of milk collect- elevated SCC , and the increased ex- the risk of spread of infection through the ing and processing companies. When penditure associated with their replace- herd . The benefits of this effect should 1,6,11,15,31,36,41,46 the cost of mastitis is estimated on a per ment . Mastitis is usually be included in the dynamic programming cow basis, data collected at the farm second only to reproduction as the largest models. 4,10,16,27,39,45,66 level needs some modelling taking into involuntary culling category . account cow numbers and mastitis occur- Financial losses at the farm level can be Premium loss and penalties (Refs 1, 25, 66, 74, 78) rence. attributed to the loss of future income and 1,15,28,31 genetic potential resulting from cull- Penalties and premium losses in many Decreased hygienic quality of milk and ing. Schepers and Dijkhuizen stated that countries, particularly the European public health considerations the loss in this case is the difference Community and Australia, are an impor- When discussing the financial implica- between the income that a particular ani- tant part of the economic losses caused by tions of mastitis, its importance in public mal could earn during her remaining mastitis. The stringent standards for a health and the effects of mastitis on expected life and the expected average number of quality parameters including the consumers should not be over- income from replacement animals with contamination with antimicrobial sub- 1,16,31,46 looked . The risk of zoonotic diseases normal productive qualities and normal stances, microbes, flavour defects, and is also an important issue. This risk, how- probabilities of disposal over the same concentration of milk components as well ever, is not necessarily associated with period of time . However, the loss occurs as somatic cells count are monitored and mastitis. The potential spread of zoonotic only when animals have to be replaced penalised or compensated for in different organisms via milk, though rare in the before reaching their optimal economic countries. Morin et al. reported 21–40 % of era of pasteurisation, remains a risk age for culling. the cost of mastitis in 4 Illinois herds especially in the niche markets of un- The decision to cull is a complex one. accounted for milk quality premium pasteurised dairy products, and during There are different ways of classifying losses . pasteurisation failures . A number of culling according to the motives that lead All costs associated with premiums loss mastitis-causing bacteria and fungi are to the culling decision. The traditional and incurred penalties at the farm level potentially pathogenic to humans, caus- concept distinguishes between voluntary are easily calculated from the statements ing in many cases severe or even fatal and involuntary culling . A different of the milk collecting and processing com- infections or intoxications (e.g. staphylo- approach has gained attention that de- panies. To estimate the cost at cow level, coccal food poisoning with the thermo- fines biologic and economic culls which calculations from the data collected at the stable toxins produced by the staphylo- allows consideration of all the factors that farm level will need modelling, taking coccae; Strep. agalactiae human septicae- influence the decision-making process . into account cow numbers and mastitis mia and neonatal meningitis etc.) . The Lehenbauer and Oltjen stated that the occurrence. In the final model estimating extensive use of antimicrobials in the culling strategies are further influenced costs of premium losses and incurred treatment and control of mastitis has pos- by short-term fluctuations in cow num- penalties the labour ’s error should be sible implications for human health bers as well as by planned herd expan- taken into account, as this will lead to through an increased risk of antimicrobial sion . However, most cows are likely to be overestimates of the cost of mastitis; for resistant strains of microbes emerging removed from dairy herds only after they example, milking of a cow before with- 1,6,60 that may then enter the food chain or have displayed several reasons that holding period is finished, etc. through the increased risk of allergic reac- would lead to culling. Farmers may con- tions. sider many cow-related factors, such as Pre-term drying off The excretion of large numbers of masti- age, stage of lactation, milk production, In many cases, particularly from mid- tis-causing organisms in milk from in- health status, disposition, reproductive lactation onward, and when there is a 56 0038-2809 Tydskr.S.Afr.vet.Ver. (2006) 77(2): 52–60 re-occurring case, pre-term drying off the directly from invoices or calculated The costs associated with education of affected quarter of a cow is advocated. To according to standard treatment and the farmers and the labour can be par- avoid underestimates of mastitis conse- prevention costs, and from labour time tially estimated from the invoices for quences all those cases should be specifi- attended courses. Time spent on educa- for monitoring, treatment, preven- 16,36,66 cally recorded and accounted for in tion is difficult to estimate. Also decreased tion , and other expenditures. 33,78 economic-loss cost evaluations . SCC were associated with the higher Expenditure on mastitis control is deter- education qualifications of the farmers or mined by which control methods are workers and not necessarily related to employed, namely: educational costs, Animal welfare aspect of mastitis knowledge about mastitis, so to try and pre-milking preparation of the udders, The welfare implications of peracute attribute this to the cost of mastitis seems teat disinfection, dry-cow therapy and toxic mastitis are obvious. Allore and somehow unrealistic. mastitis vaccines, monitoring measures, Erband Payorala stated that more recent and maintenance of the milking machine. researchers have demonstrated signifi- Pre-milking preparations of the udders On the other hand, some authors also cant secondary hyperalgesia in cows 27,52 (Refs 16, 27, 52, 66) include the treatment of clinical cases , following mild clinical episodes of masti- 1,60 The costs of this procedure include the the pre-partum treatment of heifers , tis . It has been now accepted that masti- 27,52 time the milker takes for pre-stripping, culling and the management changes tis is associated with hyperalgesia, 27,52,66 washing and drying the udders; use of in milking routine , such as milking particularly in acute and peracute cases . water and teat disinfectant for washing, infected cows last. For example, Oliver Allodynia has been demonstrated for and paper towels for drying the udders. et al. reported that pre-partum antibiotic approximately 5 and 40 days in the case of Pre-milking teat disinfection is a rela- treatment of heifers yielded net revenue mild and moderate cases of mastitis, tively new concept in mastitis control. respectively . Concentrations of brady- of around $200/heifer/year . Contagious The majority of authors conclude that this kinin, cortisol and other kinins change mastitis in the herd is associated with 21,68–70 procedure is generally effective and not during clinical mastitis . Therefore shedding of the mastitis-causing organ- 35,55,58 expensive . On the contrary, Ruegg supportive treatment of each case of isms during milking and the risk of and Dohoo reported that the reduced in- mastitis can be an issue in the near future, cross-infection to other cows in the 14,31,52,73,74 cidence of clinical cases of mastitis does leading to increased costs of mastitis. herd . In such cases the mastitis not justify the added expense incurred prevalence in the herd will change, and According to Milk Hygiene directive from pre-milking teat disinfection, with a consequently mastitis costs will be in- 92/46 EEC it is not allowed to deliver milk benefit to cost ratio of 0.37 . Further creased. A proper transition management from cows suffering from recognisable research is needed to evaluate the eco- with the added cost of feed additives, inflammation of the mammary gland . nomic impact of the procedure. minerals and vitamins in particular, play an important role in modern mastitis Associated health problems Post-milking teat disinfection control programmes. A relatively new Mastitis is commonly associated with (Refs 2, 6, 16, 23, 27, 46, 52, 66) area in mastitis control strategies is vacci- other health problems such as reproduc- When assessing the cost of teat disinfec- 25,39,46,65,74 nation against different mastitis-causing tive failure and loss of appe- tion there are 3 main elements that should 39,46,66 organisms, and some research on the tite . There will be some indirect costs be addressed, namely the cost of the teat benefits of this procedure is already avail- due to increased risk of these associated disinfectant, the installation and mainte- able. DeGraves and Fetrow estimated health problems. nance cost, and labour cost (if included as benefit of $57 per cow if the herd is vacci- Recently there has been a trend when a cost of mastitis). Gill et al. found that the nated, assuming that 1 % of the cows estimating mastitis costs to take into cost of teat disinfectants is quite variable would normally contract coliform masti- account less food consumed to produce and is influenced by the amount used per tis during the season . less milk; a factor that was not usually cow per year and the cost per litre .On 10,28 considered . However, trying to differ- top of this the cost of the emollient used entiate between loss due to inflammation Educational costs must be added. of the secretory tissue and that due to a Continuous education of farmers is a Farms that have equipment for back- decreased intake because the cow is not necessary tool in the battle against bovine flushing of the milking units should feeling well is an unrealistic sophistica- mastitis . Farmers need to be aware of include the cost of installation, mainte- tion. A healthy udder is more efficient at economic cost of mastitis in the herd and nance and any disinfectant used. converting nutrients into milk ,soto the cost benefits of a mastitis control estimate the real cost of mastitis regarding programme that will increase the farm’s Dry-cow treatment and mastitis vaccines feed intake will need a complicated net income. The cost of commercial dry-cow prod- modelling. The importance of education is demon- ucts (antimicrobials and teat sealants) is Schrick et al. reported that cows with strated by the survey conducted by Gill somewhat variable, being influenced by 6,16,23,27,46,52,66,78 clinical or sub-clinical mastitis before the et al. . They found that a regular visit by a the product used . The cost 1st service had increased days to 1st veterinarian or udder health specialist, will be influenced by the numbers of cows insemination, increased days open and more years of ownership or managing a treated at drying off if selective dry-cow increased service to conception . This farm, more education, and frequent at- therapy is used. If labour cost is consid- indicates that some of the losses from tendance at dairy extension seminars ered as an element of the mastitis cost, associated health problems can be calcu- were associated with lower SCC, while then it should be added to the calcula- lated using relatively simple model- the increase in the total number of people tions. ling.mm working on the dairy farm was associated The same procedure can be used for cal- with an increased SCC. By contrast, culation of the estimated cost of vaccines 1,16,60,66 Cost of mastitis control programmes Kuiper et al. found that the education fac- against mastitis or some of the other The costs of mastitis control include tors were not as important as premiums immuno-modulatory systems and their expenditures which can be measured and penalties applied for milk quality . application. 0038-2809 Jl S.Afr.vet.Ass. (2006) 77(2): 52–60 57 60 Monitoring measures resist disease . Nutritional relationships ACKNOWLEDGEMENTS (Ref. 23) to host defence mechanisms have led to The authors wish to thank Duncan Mac- the idea of increasing the resistance of kenzie, Colin Holmes, Tim Parkinson, SCC monitoring cost dairy cattle to mastitis through nutrition. Ross Woods and Joyce de Moulin for con- (Ref. 23) Not only gross malnutrition, but also structive comments on article. Comments The cost of herd testing is calculated merely suboptimal levels of any one from two anonymous reviewers are also easily from invoices. Herd testing is done micronutrient is sufficient to adversely greatly appreciated. by different companies around the world 29,37,59,72 affect mammary gland immunity . and these usually record the volume, pro- REFERENCES Mastitis control programmes should tein and fat content, and SCC in the milk 1. Allore H G, Erb H N 1998 Partial budget of ensure that proper levels of all macro- and from each individual cow. 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