TY - JOUR
AU - Pol, K. J. Vander
AB - ABSTRACT The effects of feeding finishing diets containing whole corn with no roughage on performance and carcass characteristics of feedlot steers were evaluated in 6 trials conducted at commercial research facilities (Bos Technica Research Services Inc., Salina, KS) in the Southern Plains of the United States. One hundred and two feedlot pens containing 6,895 steers were represented. All trials were designed as randomized complete blocks with pen serving as the experimental unit. Steers were fed and managed similarly across all trials. Treatments consisted of a typical control finishing diet with various grain sources and processing methods that contained roughage and a finishing diet containing whole corn (8 to 23% of diet DM) but without added roughage. Final BW was greater (P < 0.1) for steers fed typical finishing diets than for steers fed whole corn diets without roughage in 5 of the 6 trials. Feeding finishing diets containing whole corn but without roughage resulted in decreased (P < 0.1) ADG and carcass ADG in 5 of the 6 trials. However, DMI also was less (P < 0.1) for steers fed whole corn finishing diets without roughage in all trials such that feeding whole corn diets without roughage improved (P < 0.05) G:F (BW basis) in 2 of the 6 trials, and improved (P < 0.1) G:F based on carcass weight in 5 of the 6 trials. Dry matter intake as a percentage of BW daily across trials was well predicted from percentage of dietary NDF from roughage, being 1.906 + 0.0199 (±0.0012) NDF (P < 0.05). Performance-based NEg content of the diet was greater (P < 0.07) for steers fed whole corn diets without roughage. Differences in USDA yield and quality grades were inconsistent. Results indicate that feeding diets containing whole corn with no added roughage tends to decrease DMI and ADG in finishing steers, but improves feed efficiency and performance-calculated dietary NEg. INTRODUCTION Cereal grain is the primary constituent of most feedlot finishing diets. Grains typically are processed to increase ruminal and total tract starch digestibility and energy availability (Owens et al., 1997). Roughage traditionally is included in finishing diets, but quantities are typically small (<10% of diet DM); roughage is fed to maintain rumen health and to reduce the incidence of digestive disorders including bloat, acidosis, liver abscesses, and laminitis (Nagaraja and Lechtenberg, 2007). Unfortunately, including roughage in finishing diets reduces dietary NEg, increases the cost per unit of ME, and complicates diet handling and management at commercial feedlots (Britton and Stock, 1987). Although removal of roughage from finishing diets has management, economic, and caloric density advantages, roughage-free diets must be formulated carefully to mitigate digestive disorders and to optimize growth performance. One approach for eliminating roughage from finishing diets is to provide whole corn in the diet. Because it is not processed, whole corn has slower rate and less extent of ruminal starch digestion when compared with steam-flaked and high-moisture corn (Britton and Stock, 1987). Therefore, feeding whole corn should help to avoid digestive disorders by regulating ruminal starch fermentation and reducing accumulation of organic acids in the rumen. Although whole corn has been fed successfully to finishing cattle in all-concentrate diets in research trials (Vance et al., 1972; Traxler et al., 1995; Loerch and Fluharty, 1998), direct comparisons with diets composed of traditionally processed grain sources (i.e., dry-rolled, high-moisture, and steam-flaked grains) are lacking. Further, no trials have evaluated these finishing regimens in a large pen, commercial feedlot setting. Accordingly, the objective of these trials was to evaluate the effects of feeding diets containing whole corn, but no roughage on performance, health, and carcass characteristics of steers finished at a commercial feedyard. MATERIALS AND METHODS All trials were approved by the animal care and use guidelines set forth by Bos-Technica Research Services Inc. (Salina, KS). Research Sites Six large-pen feedlot trials (designated trials 1 to 6) involving 102 pens with 6,895 steers (mean BW 288 to 341 kg) were conducted to determine response to substituting whole corn-no roughage diets for traditional diets on performance, health, and carcass characteristics of finishing steers. Trials were conducted in the Southern Plains of the United States. Research sites included commercial feedyards near Stratford, TX, and Oberlin, KS (Table 1) managed by Bos-Technica Research Services Inc. Feedlot pens were dirt-floored and accommodated 36 to 82 steers. Pens were equipped with constant flow water tanks and had mounds that ran perpendicular to the feed bunks and aprons. A research manager and support staff were on-site to supervise daily activities during each trial. Table 1. Design attributes for finishing trials evaluating diets containing whole corn and no roughage Item  Trial  1  2  3  4  5  6  Site location  TX  KS  TX  TX  TX  TX  n1  996  457  1,702  1,464  1,383  893  Origin  TX  MO  OK  CO  NM  TX, KS  Replicates2  6  6  12  12  3  4  Steers/pen  82  36  70  60  75  72  Item  Trial  1  2  3  4  5  6  Site location  TX  KS  TX  TX  TX  TX  n1  996  457  1,702  1,464  1,383  893  Origin  TX  MO  OK  CO  NM  TX, KS  Replicates2  6  6  12  12  3  4  Steers/pen  82  36  70  60  75  72  1Number of steers. 2Pens fed/dietary treatment. View Large Table 1. Design attributes for finishing trials evaluating diets containing whole corn and no roughage Item  Trial  1  2  3  4  5  6  Site location  TX  KS  TX  TX  TX  TX  n1  996  457  1,702  1,464  1,383  893  Origin  TX  MO  OK  CO  NM  TX, KS  Replicates2  6  6  12  12  3  4  Steers/pen  82  36  70  60  75  72  Item  Trial  1  2  3  4  5  6  Site location  TX  KS  TX  TX  TX  TX  n1  996  457  1,702  1,464  1,383  893  Origin  TX  MO  OK  CO  NM  TX, KS  Replicates2  6  6  12  12  3  4  Steers/pen  82  36  70  60  75  72  1Number of steers. 2Pens fed/dietary treatment. View Large Processing and Allotment of Cattle After arrival, steers were allowed to rest in receiving pens for up to 24 h before being processed. During their receiving period, steers had free choice access to long-stemmed grass or alfalfa hay, water, and a diet formulated to contain a minimum of 13.5% CP, 1.1 Mcal of NEg/kg, 0.86% Ca, 0.26% salt, and 1.30% K (DM basis). A randomized complete block experimental design was used in each trial, with receiving date serving as the blocking factor. Steers within each block were allowed to commingle at the time of allotment. Steers then were placed into a sorting alley where they were allotted randomly to pens, 10 at a time, until all pens were filled (50 to 100 steers/pen). Cattle in a pen were weighed as a group using a certified platform scale that was balanced between drafts. Within each block, pens were assigned randomly to treatment (4 to 12 pens/treatment in each trial). After allotment, cattle were moved through a hydraulic chute where they each received a lot tag, an implant (STEER-oid, 200 mg of progesterone and 20 mg of estradiol, Anchor Laboratories Inc., St. Joseph, MO), and a vitamin injection (1 × 106 IU of vitamin A and 1.5 × 105 IU of vitamin D; Schering Plough Animal Health, Union, NJ). Cattle also received subcutaneous injections of ivermectin (Ivomec, Merial, Athens, GA), a multivalent clostridial bacterin-toxoid (Bar-Vac 7, Boehringer Ingelheim, Ridgefield, CT), and a respiratory vaccine containing modified-live bovine herpes virus and Leptospira pomona bacterin (Sanofi Animal Health, Lenexa, KS). This processing regimen was used in each trial with the following exceptions: 1) 158 steers enrolled in trial 2 were not vaccinated with a clostridial bacterin-toxoid and were not treated for parasites, 2) 300 steers enrolled in trial 2 received a combination respiratory vaccine (CattleMaster 4+L5, Pfizer Animal Health, Exton, PA) in place of a vaccine containing only bovine herpes virus and L. pomona, and 3) steers enrolled in trial 2 received the initial implant alone or in combination with Finaplix-S (140 mg of trenbolone acetate, Hoechst-Roussel, Millsboro, DE). Steers enrolled in trials 2, 3, and 4 were re-implanted with STEER-oid on d 48, 69, or 50 of the study, respectively. Dietary Treatments and Feeding Management Dietary treatments consisted of a control diet containing a roughage source (CON) or a diet containing whole corn, but without roughage (NR; Table 2). In trials 1 and 2, an additional treatment (COMB) was included that consisted of the control and no-roughage treatments fed sequentially during the feeding period. A control and 2 no-roughage treatments containing 7.5 or 15% whole corn also were tested in trial 6 (Table 3). It is important to note that treatments in which whole corn replaced only the roughage portion of the diet were not specifically tested in this series of trials. Therefore, it is not possible for us to exclusively attribute the observed effects to roughage removal, whole corn addition, or the change in amounts of the other dietary ingredients. Table 2. Composition of feedlot finishing diets fed during trials 1 to 51 Item  Trial 1  Trial 2  Trial 3  Trial 4  Trial 5  CON  NR  CON  NR  CON  NR  CON  NR  CON  NR  Ingredient, % of DM                                 Dry-rolled corn  —  —  43  34.3  —  —  11.4  11.5  —  —   High-moisture corn  22.5  18.4  —  —  14.1  15  26.2  26.7  19.8  24.8   Whole corn  —  22.7  —  22.8  —  8.5  —  8.4  —  7.5   Steam-flaked milo  59.9  49.9  41.8  32.8  22.9  22.9  —  —  61.4  58.4   Steam-flaked wheat  —  —  —  —  44.2  44.2  43.6  43.5  —  —   Alfalfa hay  4.3  —  —  —  6.9  —  10  —  7.1  —   Alfalfa pellet  —  —  6.6  —  —  —  —  —  —  —   Sorghum silage  —  —  —  —  3.2  —  —  —  3  —   Cottonseed hulls  4.5  —  —  —  —  —  —  —  —  —   Tallow  3.7  3.7  3.6  3.3  4.9  4.9  4.7  4.7  4  4   Supplement  5.1  5.3  5  6.8  3.8  4.5  4.1  5.2  4.7  5.3  Analyzed nutrient composition, % of DM                        DM  80.7  80.9  83.6  84.2  81.4  82.3  82.4  81.9  76.9  80.9   CP  12.6  12.3  12.4  12  12.1  12.2  12  12.2  12.6  12.4   Crude fiber  6.6  3.6  5.5  3.2  6  3.3  6.2  3.5  5.7  3.1   Fat  6.6  6.8  6.6  6.8  7.2  7.3  7.1  7.3  6.8  7   Ca  0.65  0.6  0.66  0.64  0.68  0.62  0.68  0.62  0.62  0.6   P  0.34  0.34  0.39  0.39  0.33  0.35  0.33  0.37  0.3  0.29   K  0.66  0.6  0.64  0.54  0.71  0.52  0.71  0.55  0.76  0.68   NPN  1.7  1.8  1.9  2.2  0.72  1.1  0.61  1.3  1.8  2   Salt  0.4  0.4  0.3  0.35  0.23  0.24  0.24  0.26  0.4  0.4  Monensin,2 mg/kg  30  30  30  30  33  33  33  33  30  30  Tylosin,2 mg/kg  9  9  8  8  11  11  11  11  11  11  Item  Trial 1  Trial 2  Trial 3  Trial 4  Trial 5  CON  NR  CON  NR  CON  NR  CON  NR  CON  NR  Ingredient, % of DM                                 Dry-rolled corn  —  —  43  34.3  —  —  11.4  11.5  —  —   High-moisture corn  22.5  18.4  —  —  14.1  15  26.2  26.7  19.8  24.8   Whole corn  —  22.7  —  22.8  —  8.5  —  8.4  —  7.5   Steam-flaked milo  59.9  49.9  41.8  32.8  22.9  22.9  —  —  61.4  58.4   Steam-flaked wheat  —  —  —  —  44.2  44.2  43.6  43.5  —  —   Alfalfa hay  4.3  —  —  —  6.9  —  10  —  7.1  —   Alfalfa pellet  —  —  6.6  —  —  —  —  —  —  —   Sorghum silage  —  —  —  —  3.2  —  —  —  3  —   Cottonseed hulls  4.5  —  —  —  —  —  —  —  —  —   Tallow  3.7  3.7  3.6  3.3  4.9  4.9  4.7  4.7  4  4   Supplement  5.1  5.3  5  6.8  3.8  4.5  4.1  5.2  4.7  5.3  Analyzed nutrient composition, % of DM                        DM  80.7  80.9  83.6  84.2  81.4  82.3  82.4  81.9  76.9  80.9   CP  12.6  12.3  12.4  12  12.1  12.2  12  12.2  12.6  12.4   Crude fiber  6.6  3.6  5.5  3.2  6  3.3  6.2  3.5  5.7  3.1   Fat  6.6  6.8  6.6  6.8  7.2  7.3  7.1  7.3  6.8  7   Ca  0.65  0.6  0.66  0.64  0.68  0.62  0.68  0.62  0.62  0.6   P  0.34  0.34  0.39  0.39  0.33  0.35  0.33  0.37  0.3  0.29   K  0.66  0.6  0.64  0.54  0.71  0.52  0.71  0.55  0.76  0.68   NPN  1.7  1.8  1.9  2.2  0.72  1.1  0.61  1.3  1.8  2   Salt  0.4  0.4  0.3  0.35  0.23  0.24  0.24  0.26  0.4  0.4  Monensin,2 mg/kg  30  30  30  30  33  33  33  33  30  30  Tylosin,2 mg/kg  9  9  8  8  11  11  11  11  11  11  1CON = roughage diet; NR = no roughage diet containing whole corn. 2Monensin (Rumensin, Elanco Animal Health, Indianapolis, IN); tylosin (Tylan, Elanco Animal Health). View Large Table 2. Composition of feedlot finishing diets fed during trials 1 to 51 Item  Trial 1  Trial 2  Trial 3  Trial 4  Trial 5  CON  NR  CON  NR  CON  NR  CON  NR  CON  NR  Ingredient, % of DM                                 Dry-rolled corn  —  —  43  34.3  —  —  11.4  11.5  —  —   High-moisture corn  22.5  18.4  —  —  14.1  15  26.2  26.7  19.8  24.8   Whole corn  —  22.7  —  22.8  —  8.5  —  8.4  —  7.5   Steam-flaked milo  59.9  49.9  41.8  32.8  22.9  22.9  —  —  61.4  58.4   Steam-flaked wheat  —  —  —  —  44.2  44.2  43.6  43.5  —  —   Alfalfa hay  4.3  —  —  —  6.9  —  10  —  7.1  —   Alfalfa pellet  —  —  6.6  —  —  —  —  —  —  —   Sorghum silage  —  —  —  —  3.2  —  —  —  3  —   Cottonseed hulls  4.5  —  —  —  —  —  —  —  —  —   Tallow  3.7  3.7  3.6  3.3  4.9  4.9  4.7  4.7  4  4   Supplement  5.1  5.3  5  6.8  3.8  4.5  4.1  5.2  4.7  5.3  Analyzed nutrient composition, % of DM                        DM  80.7  80.9  83.6  84.2  81.4  82.3  82.4  81.9  76.9  80.9   CP  12.6  12.3  12.4  12  12.1  12.2  12  12.2  12.6  12.4   Crude fiber  6.6  3.6  5.5  3.2  6  3.3  6.2  3.5  5.7  3.1   Fat  6.6  6.8  6.6  6.8  7.2  7.3  7.1  7.3  6.8  7   Ca  0.65  0.6  0.66  0.64  0.68  0.62  0.68  0.62  0.62  0.6   P  0.34  0.34  0.39  0.39  0.33  0.35  0.33  0.37  0.3  0.29   K  0.66  0.6  0.64  0.54  0.71  0.52  0.71  0.55  0.76  0.68   NPN  1.7  1.8  1.9  2.2  0.72  1.1  0.61  1.3  1.8  2   Salt  0.4  0.4  0.3  0.35  0.23  0.24  0.24  0.26  0.4  0.4  Monensin,2 mg/kg  30  30  30  30  33  33  33  33  30  30  Tylosin,2 mg/kg  9  9  8  8  11  11  11  11  11  11  Item  Trial 1  Trial 2  Trial 3  Trial 4  Trial 5  CON  NR  CON  NR  CON  NR  CON  NR  CON  NR  Ingredient, % of DM                                 Dry-rolled corn  —  —  43  34.3  —  —  11.4  11.5  —  —   High-moisture corn  22.5  18.4  —  —  14.1  15  26.2  26.7  19.8  24.8   Whole corn  —  22.7  —  22.8  —  8.5  —  8.4  —  7.5   Steam-flaked milo  59.9  49.9  41.8  32.8  22.9  22.9  —  —  61.4  58.4   Steam-flaked wheat  —  —  —  —  44.2  44.2  43.6  43.5  —  —   Alfalfa hay  4.3  —  —  —  6.9  —  10  —  7.1  —   Alfalfa pellet  —  —  6.6  —  —  —  —  —  —  —   Sorghum silage  —  —  —  —  3.2  —  —  —  3  —   Cottonseed hulls  4.5  —  —  —  —  —  —  —  —  —   Tallow  3.7  3.7  3.6  3.3  4.9  4.9  4.7  4.7  4  4   Supplement  5.1  5.3  5  6.8  3.8  4.5  4.1  5.2  4.7  5.3  Analyzed nutrient composition, % of DM                        DM  80.7  80.9  83.6  84.2  81.4  82.3  82.4  81.9  76.9  80.9   CP  12.6  12.3  12.4  12  12.1  12.2  12  12.2  12.6  12.4   Crude fiber  6.6  3.6  5.5  3.2  6  3.3  6.2  3.5  5.7  3.1   Fat  6.6  6.8  6.6  6.8  7.2  7.3  7.1  7.3  6.8  7   Ca  0.65  0.6  0.66  0.64  0.68  0.62  0.68  0.62  0.62  0.6   P  0.34  0.34  0.39  0.39  0.33  0.35  0.33  0.37  0.3  0.29   K  0.66  0.6  0.64  0.54  0.71  0.52  0.71  0.55  0.76  0.68   NPN  1.7  1.8  1.9  2.2  0.72  1.1  0.61  1.3  1.8  2   Salt  0.4  0.4  0.3  0.35  0.23  0.24  0.24  0.26  0.4  0.4  Monensin,2 mg/kg  30  30  30  30  33  33  33  33  30  30  Tylosin,2 mg/kg  9  9  8  8  11  11  11  11  11  11  1CON = roughage diet; NR = no roughage diet containing whole corn. 2Monensin (Rumensin, Elanco Animal Health, Indianapolis, IN); tylosin (Tylan, Elanco Animal Health). View Large Table 3. Composition (DM basis) of feedlot finishing diets fed during trial 61 Item  CON  7.5WC  15WC  Ingredient, % of DM            High-moisture corn  32.4  31  23.4   Whole corn  —  7.9  15.6   Steam-flaked milo  51.2  51.2  51.2   Alfalfa hay  7.8  —  —   Tallow  3.8  3.8  3.8   Supplement  4.8  6.1  6  Analyzed nutrient composition, % of DM          DM  81.4  80.9  81.9   CP  12.4  12.3  12.3   Crude fiber  5.7  3.6  3.6   Fat  6.9  7  6.9   Ca  0.66  0.69  0.68   P  0.34  0.36  0.35   K  0.67  0.65  0.67   NPN  1.7  1.7  1.7   Salt  0.31  0.36  0.33  Monensin,2 mg/kg  31  31  31  Tylosin,2 mg/kg  9  9  9  Item  CON  7.5WC  15WC  Ingredient, % of DM            High-moisture corn  32.4  31  23.4   Whole corn  —  7.9  15.6   Steam-flaked milo  51.2  51.2  51.2   Alfalfa hay  7.8  —  —   Tallow  3.8  3.8  3.8   Supplement  4.8  6.1  6  Analyzed nutrient composition, % of DM          DM  81.4  80.9  81.9   CP  12.4  12.3  12.3   Crude fiber  5.7  3.6  3.6   Fat  6.9  7  6.9   Ca  0.66  0.69  0.68   P  0.34  0.36  0.35   K  0.67  0.65  0.67   NPN  1.7  1.7  1.7   Salt  0.31  0.36  0.33  Monensin,2 mg/kg  31  31  31  Tylosin,2 mg/kg  9  9  9  1CON = roughage diet; 7.5WC = no roughage diet containing 7.5% of diet DM as whole corn; 15WC = no roughage diet containing 15% of diet DM as whole corn. 2Monensin (Rumensin, Elanco Animal Health, Indianapolis, IN); tylosin (Tylan, Elanco Animal Health). View Large Table 3. Composition (DM basis) of feedlot finishing diets fed during trial 61 Item  CON  7.5WC  15WC  Ingredient, % of DM            High-moisture corn  32.4  31  23.4   Whole corn  —  7.9  15.6   Steam-flaked milo  51.2  51.2  51.2   Alfalfa hay  7.8  —  —   Tallow  3.8  3.8  3.8   Supplement  4.8  6.1  6  Analyzed nutrient composition, % of DM          DM  81.4  80.9  81.9   CP  12.4  12.3  12.3   Crude fiber  5.7  3.6  3.6   Fat  6.9  7  6.9   Ca  0.66  0.69  0.68   P  0.34  0.36  0.35   K  0.67  0.65  0.67   NPN  1.7  1.7  1.7   Salt  0.31  0.36  0.33  Monensin,2 mg/kg  31  31  31  Tylosin,2 mg/kg  9  9  9  Item  CON  7.5WC  15WC  Ingredient, % of DM            High-moisture corn  32.4  31  23.4   Whole corn  —  7.9  15.6   Steam-flaked milo  51.2  51.2  51.2   Alfalfa hay  7.8  —  —   Tallow  3.8  3.8  3.8   Supplement  4.8  6.1  6  Analyzed nutrient composition, % of DM          DM  81.4  80.9  81.9   CP  12.4  12.3  12.3   Crude fiber  5.7  3.6  3.6   Fat  6.9  7  6.9   Ca  0.66  0.69  0.68   P  0.34  0.36  0.35   K  0.67  0.65  0.67   NPN  1.7  1.7  1.7   Salt  0.31  0.36  0.33  Monensin,2 mg/kg  31  31  31  Tylosin,2 mg/kg  9  9  9  1CON = roughage diet; 7.5WC = no roughage diet containing 7.5% of diet DM as whole corn; 15WC = no roughage diet containing 15% of diet DM as whole corn. 2Monensin (Rumensin, Elanco Animal Health, Indianapolis, IN); tylosin (Tylan, Elanco Animal Health). View Large Steers were adapted to their respective dietary treatments using a series of 4 transition diets. Complete diets were compiled by combining specified amounts of dry-rolled, high-moisture, or whole corn, steam-flaked milo, steam-flaked wheat, alfalfa hay, alfalfa pellets, sorghum silage, cottonseed hulls, tallow, and supplement in a horizontal truck-mounted mixer. Diets were formulated to contain a minimum of 12% CP, 6% fat, 30 mg/kg of monensin (Rumensin, Elanco Animal Health, Indianapolis, IN), 9 mg/kg of tylosin (Tylan, Elanco Animal Health), and 0.6% Ca (DM basis). Diets were fed twice daily in equal portions, and the amount of feed delivered to each pen was adjusted daily by assessing behavioral responses of steers to their first daily feed delivery and by the amount of feed remaining in the bunk at the time of appraisal. Steers were fed amounts of feed so that only trace amounts of diet remained in the feed bunk before their next feed delivery. Feeding management procedures were consistent across studies with 1 exception. In trial 1, one-half of the pens received excess feed on the day before slaughter so that feed remained in the bunk after the steers were removed for slaughter. The quantity of diet delivered to each pen was recorded daily. Feed refusals were removed, weighed, and a representative sample was obtained for moisture determination by drying 100 g of fresh sample in a forced-air oven for 24 h at 100°C. Representative samples of each diet were obtained from 3 locations throughout the feedbunk after the first feeding each day, but before steers had disrupted the mix. Samples were submitted to SDK Laboratories (Hutchinson, KS) for moisture determination and analysis for CP, crude fiber, fat, Ca, P, and K (AOAC, 1990). Representative samples of feed ingredients also were obtained for moisture determination as described previously. Laboratory analyses were monitored to ensure that ingredient and nutrient composition coincided with values achieved at the time diets were formulated. Feed truck scale systems were checked frequently by a certified technician. In addition, weights of 1 or more batches from each feed truck were checked against a platform scale each week. Scales were recalibrated whenever an inaccuracy greater than 1% deviation (22 kg) was noted. Diets were delivered to pens within a 9-kg tolerance, and excess feed delivered was removed from the bunk if more than 9 kg of the specified amount was delivered. Daily feed delivery and refusal records for each pen after correction for moisture content were used to calculate DMI for the pen. Cattle Health Health status of steers in each pen was monitored at least once each day by experienced feedlot personnel. Steers exhibiting abnormal behavior or clinical signs of disease were moved to a hospital pen, identified by a hospital tag, and treated as prescribed by a licensed veterinarian. The control diet was fed to cattle housed in hospital pens. Steers that recovered from disease were returned to their assigned (home) pens. Steers that did not recover from disease, were in a hospital pen for more than 10 consecutive days, were removed to a hospital pen for the same disease condition 4 or more times, were crippled, were designated as bullers, or were treated surgically for bloat were removed from the study. During the time in which an animal resided in a hospital, feed consumption was recorded as being 50% of mean daily DMI of the respective home pen of the animal. Collection of Carcass Data Final BW was obtained by weighing steers by pen immediately before transport to a USDA-inspected slaughter facility in Amarillo, TX, with 1 exception. Steers in trial 2 were transported to and slaughtered at a USDA-inspected facility in Dodge City, KS. Initial BW, final BW adjusted for a 4% shrink, and DMI records were used to compute ADG and feed conversion. Dead and reject cattle were not included in the computation for final pen BW. Tabular (expected) diet NEg was computed using reported values (NRC, 1996). Supplement, cottonseed hulls, and steam-flaked wheat were considered to contain 0.7, 0.15, and 1.54 of Mcal of NEg/kg, respectively. Diet NEg content was also estimated from feedlot performance (observed; NRC, 1996) using an iterative approach (Owens et al., 2002). Equivalent BW was assumed to be 591 kg. Hot carcass weight and USDA yield and quality grade were collected by trained personnel. Carcass-basis performance (i.e., ADG and G:F) was calculated from initial carcass weight (initial BW × 55%; MacDonald et al., 2007) and HCW. Total days on feed ranged from 134 to 175. Steers assigned CON and NR treatments were fed their experimental diets for 111 to 158 and 98 to 158 d, respectively. In trials 3, 4, and 5, some steers were slaughtered 28 d beyond the projected endpoint (trials 3 and 4) or 21 and 35 d beyond the projected endpoint (trial 5). Statistical Analysis These trials were designed such that a minimum of 0.0077 unit difference in G:F and a 14% difference in USDA Choice could be detected between treatments (α < 0.05; β < 0.2; Turgeon and Koers, 1997). Data were analyzed as a randomized complete block using the MIXED procedure (SAS Inst. Inc., Cary, NC) with the respective number of dietary treatments. The statistical model accounted for the overall mean, the fixed effect of dietary treatment, the random effect of block, and a residual error term. Pen served as the experimental unit. Treatment means were partitioned using Fisher's LSD test (PDIFF option) when the overall effect of dietary treatment was significant (P < 0.10). The main effect of replacing roughage with whole corn in trial 6 also was tested using a single degree of freedom orthogonal contrast. Interactions were tested for trials involving factorialized treatment arrangements. In the event the interaction was significant (P < 0.05), treatment least squares means were partitioned using the PDIFF option mentioned previously; differences between treatment means were deemed significant at α < 0.1. Additionally, main effect of dietary treatment was tested within each factor subclass when an interaction was detected (Winer, 1971). Only the main effects of dietary treatment are shown when the interaction was not significant (P > 0.1). RESULTS AND DISCUSSION Interactions between the effects of dietary treatment and effects of other imposed treatments were not detected (P > 0.1) in trials 1, 2, 3, 4, or 6. Final BW was greater (P < 0.03) for CON than NR treatments in trials 1, 3, 4, and 5 but was similar (P > 0.2) between CON and NR treatments in trial 2 (Tables 4 and 5). Dry matter intake favored CON (P < 0.004) relative to other dietary treatments in all trials, whereas ADG (live- and carcass-basis) favored CON (P < 0.002) relative to other dietary treatments in trials 1, 3, 4, and 6 (Tables 4, 5, and 6). In trial 2, G:F was superior (P < 0.03) for NR compared with CON. Carcass feed conversion was superior (P < 0.1) for NR compared with CON in trials 1, 2, 3, and 4. Hot carcass weight was greater (P < 0.08) for CON-fed steers compared with steers fed whole corn diets without roughage. Mortality was similar (P > 0.13) across treatments, averaging 0.36%. Performance-based diet NEg was increased (P < 0.07) as a result of feeding diets containing whole corn without roughage relative to controls in trials 1, 2, 3, and 5, and with feeding 7.5% whole corn in trial 6 (Table 7). Few differences from feeding COMB were noted, and these differences were inconsistent. In trial 2, final BW and DMI were greater (P ≤ 0.05) for COMB compared with CON, but in trial 1, DMI and ADG were less (P < 0.001) and feed conversion was poorer (P < 0.02) for COMB relative to CON. Unlike the differences noted with NR treatments, COMB yielded no improvement (P > 0.16) in diet NEg content. Table 4. Effect of dietary treatment on live performance for trials 1 to 4 Item1  Trial  1  2  3  4  DOF2  143  170  161  143  DOR3               CON  128  150  145  125   NR  123  141  131  112   COMB  51/77  77/73  —  —  Initial BW, kg               CON  337.6  304.3  308.4  327.4   NR  337.4  306.5  309.7  328.1   COMB  338.8  308.6  —  —   SEM  2  3  1.1  1.4   P-value  0.87  0.37  0.34  0.72  Final BW, kg               CON  523.3b  544.1a  518.1  514.3   NR  510.5a  550.3ab  507.2  504.7   COMB  512.4a  556.0b  —  —   SEM  3.9  2.8  3.9  1.9   P-value  0.03  0.05  0.002  0.002  DMI, kg/d               CON  8.47c  9.18b  7.99  8.13   NR  7.79a  8.93a  7.46  7.74   COMB  8.08b  9.42c  —  —   SEM  0.06  0.1  0.05  0.05   P-value  0.001  0.004  0.001  0.001  ADG, kg               CON  1.30b  1.41  1.31  1.31   NR  1.21a  1.43  1.23  1.24   COMB  1.21a  1.46  —  —   SEM  0.02  0.02  0.02  0.01   P-value  0.001  0.25  0.001  0.001  G:F               CON  0.153a  0.154b  0.163  0.16   NR  0.155a  0.161a  0.165  0.159   COMB  0.150b  0.155b  —  —   SEM  0.0014  0.0016  0.0017  0.0019   P-value  0.02  0.03  0.24  0.12  Item1  Trial  1  2  3  4  DOF2  143  170  161  143  DOR3               CON  128  150  145  125   NR  123  141  131  112   COMB  51/77  77/73  —  —  Initial BW, kg               CON  337.6  304.3  308.4  327.4   NR  337.4  306.5  309.7  328.1   COMB  338.8  308.6  —  —   SEM  2  3  1.1  1.4   P-value  0.87  0.37  0.34  0.72  Final BW, kg               CON  523.3b  544.1a  518.1  514.3   NR  510.5a  550.3ab  507.2  504.7   COMB  512.4a  556.0b  —  —   SEM  3.9  2.8  3.9  1.9   P-value  0.03  0.05  0.002  0.002  DMI, kg/d               CON  8.47c  9.18b  7.99  8.13   NR  7.79a  8.93a  7.46  7.74   COMB  8.08b  9.42c  —  —   SEM  0.06  0.1  0.05  0.05   P-value  0.001  0.004  0.001  0.001  ADG, kg               CON  1.30b  1.41  1.31  1.31   NR  1.21a  1.43  1.23  1.24   COMB  1.21a  1.46  —  —   SEM  0.02  0.02  0.02  0.01   P-value  0.001  0.25  0.001  0.001  G:F               CON  0.153a  0.154b  0.163  0.16   NR  0.155a  0.161a  0.165  0.159   COMB  0.150b  0.155b  —  —   SEM  0.0014  0.0016  0.0017  0.0019   P-value  0.02  0.03  0.24  0.12  a–cMeans within trial and performance measure without a common superscript differ (P < 0.05). 1CON = roughage diet; NR = no roughage diet containing whole corn; COMB = steers fed CON diet followed by NR diet. 2DOF = average days on feed. 3DOR = days on experimental diet; for COMB treatment, DOR for CON and NR is partitioned using a forward slash. View Large Table 4. Effect of dietary treatment on live performance for trials 1 to 4 Item1  Trial  1  2  3  4  DOF2  143  170  161  143  DOR3               CON  128  150  145  125   NR  123  141  131  112   COMB  51/77  77/73  —  —  Initial BW, kg               CON  337.6  304.3  308.4  327.4   NR  337.4  306.5  309.7  328.1   COMB  338.8  308.6  —  —   SEM  2  3  1.1  1.4   P-value  0.87  0.37  0.34  0.72  Final BW, kg               CON  523.3b  544.1a  518.1  514.3   NR  510.5a  550.3ab  507.2  504.7   COMB  512.4a  556.0b  —  —   SEM  3.9  2.8  3.9  1.9   P-value  0.03  0.05  0.002  0.002  DMI, kg/d               CON  8.47c  9.18b  7.99  8.13   NR  7.79a  8.93a  7.46  7.74   COMB  8.08b  9.42c  —  —   SEM  0.06  0.1  0.05  0.05   P-value  0.001  0.004  0.001  0.001  ADG, kg               CON  1.30b  1.41  1.31  1.31   NR  1.21a  1.43  1.23  1.24   COMB  1.21a  1.46  —  —   SEM  0.02  0.02  0.02  0.01   P-value  0.001  0.25  0.001  0.001  G:F               CON  0.153a  0.154b  0.163  0.16   NR  0.155a  0.161a  0.165  0.159   COMB  0.150b  0.155b  —  —   SEM  0.0014  0.0016  0.0017  0.0019   P-value  0.02  0.03  0.24  0.12  Item1  Trial  1  2  3  4  DOF2  143  170  161  143  DOR3               CON  128  150  145  125   NR  123  141  131  112   COMB  51/77  77/73  —  —  Initial BW, kg               CON  337.6  304.3  308.4  327.4   NR  337.4  306.5  309.7  328.1   COMB  338.8  308.6  —  —   SEM  2  3  1.1  1.4   P-value  0.87  0.37  0.34  0.72  Final BW, kg               CON  523.3b  544.1a  518.1  514.3   NR  510.5a  550.3ab  507.2  504.7   COMB  512.4a  556.0b  —  —   SEM  3.9  2.8  3.9  1.9   P-value  0.03  0.05  0.002  0.002  DMI, kg/d               CON  8.47c  9.18b  7.99  8.13   NR  7.79a  8.93a  7.46  7.74   COMB  8.08b  9.42c  —  —   SEM  0.06  0.1  0.05  0.05   P-value  0.001  0.004  0.001  0.001  ADG, kg               CON  1.30b  1.41  1.31  1.31   NR  1.21a  1.43  1.23  1.24   COMB  1.21a  1.46  —  —   SEM  0.02  0.02  0.02  0.01   P-value  0.001  0.25  0.001  0.001  G:F               CON  0.153a  0.154b  0.163  0.16   NR  0.155a  0.161a  0.165  0.159   COMB  0.150b  0.155b  —  —   SEM  0.0014  0.0016  0.0017  0.0019   P-value  0.02  0.03  0.24  0.12  a–cMeans within trial and performance measure without a common superscript differ (P < 0.05). 1CON = roughage diet; NR = no roughage diet containing whole corn; COMB = steers fed CON diet followed by NR diet. 2DOF = average days on feed. 3DOR = days on experimental diet; for COMB treatment, DOR for CON and NR is partitioned using a forward slash. View Large Table 5. Effect of dietary treatment on growth performance and carcass characteristics for trial 6 Item  Dietary treatment1  SEM  P-value  CON  7.5WC  15WC  DOF2  167  167  167  —  —  DOR3  150  142  142  —  —  Performance                  Live                   Initial BW, kg  287.6  287.6  288.9  0.92  0.54    Final BW,4,5 kg  513.2  506.3  507.3  2.8  0.08    DMI,5 kg/d  7.84  7.46  7.54  0.046  0.002    ADG,5 kg  1.35  1.31  1.31  0.017  0.11    G:F  0.172  0.176  0.173  0.0015  0.25   Carcass                   HCW,5 kg  333.6  329.6  329.7  2.05  0.19    ADG,5,6 kg  1.05  1.03  1.02  0.013  0.22    G:F5,6  0.134  0.138  0.136  0.0011  0.09  Mortality, %  0.68  0.34  0.67  0.37  0.78  Tabular NEg,7 Mcal/kg   1.53  1.58  1.58  —  —  Performance NEg,7 Mcal/kg  1.42a  1.47b  1.45a  0.008  0.01  Dressing percentage  65  65.1  65  0.13  0.82  USDA yield grade, %                  1  4.46  4.08  3.91  2  0.97   2  31.8  36  34.8  3.3  0.65   3  55.4  55.9  55.8  4.5  1   45  7.88  4.1  5.51  1.4  0.23  USDA quality grade, %                  Prime  1.72  1.73  2.7  1.3  0.76   Choice5  71.9  68.2  66.2  2.3  0.15   Choice + Prime  73.6  69.9  68.9  2.9  0.4   Select  26  30.1  30.7  2.9  0.36  Item  Dietary treatment1  SEM  P-value  CON  7.5WC  15WC  DOF2  167  167  167  —  —  DOR3  150  142  142  —  —  Performance                  Live                   Initial BW, kg  287.6  287.6  288.9  0.92  0.54    Final BW,4,5 kg  513.2  506.3  507.3  2.8  0.08    DMI,5 kg/d  7.84  7.46  7.54  0.046  0.002    ADG,5 kg  1.35  1.31  1.31  0.017  0.11    G:F  0.172  0.176  0.173  0.0015  0.25   Carcass                   HCW,5 kg  333.6  329.6  329.7  2.05  0.19    ADG,5,6 kg  1.05  1.03  1.02  0.013  0.22    G:F5,6  0.134  0.138  0.136  0.0011  0.09  Mortality, %  0.68  0.34  0.67  0.37  0.78  Tabular NEg,7 Mcal/kg   1.53  1.58  1.58  —  —  Performance NEg,7 Mcal/kg  1.42a  1.47b  1.45a  0.008  0.01  Dressing percentage  65  65.1  65  0.13  0.82  USDA yield grade, %                  1  4.46  4.08  3.91  2  0.97   2  31.8  36  34.8  3.3  0.65   3  55.4  55.9  55.8  4.5  1   45  7.88  4.1  5.51  1.4  0.23  USDA quality grade, %                  Prime  1.72  1.73  2.7  1.3  0.76   Choice5  71.9  68.2  66.2  2.3  0.15   Choice + Prime  73.6  69.9  68.9  2.9  0.4   Select  26  30.1  30.7  2.9  0.36  a,bMeans within trial and performance measure without a common superscript differ (P < 0.05). 1CON = roughage diet; 7.5WC = no roughage diet containing 7.5% of diet DM as whole corn; 15WC = no roughage diet containing 15% of diet DM as whole corn. 2DOF = average days on feed. 3DOR = days on experimental diet. 44% pencil shrink applied to final BW. 5Roughage vs. whole corn diets (P < 0.10). 6Carcass performance calculated using initial carcass weight (initial BW × 55%; MacDonald et al., 2007) and HCW. 7Tabular NEg computed using tabular ingredient energy values reported in the NRC (1996); performance-based NEg computed from DMI and BW data with a 4% shrink applied (NRC, 1996); equivalent BW was assumed to be 591 kg. View Large Table 5. Effect of dietary treatment on growth performance and carcass characteristics for trial 6 Item  Dietary treatment1  SEM  P-value  CON  7.5WC  15WC  DOF2  167  167  167  —  —  DOR3  150  142  142  —  —  Performance                  Live                   Initial BW, kg  287.6  287.6  288.9  0.92  0.54    Final BW,4,5 kg  513.2  506.3  507.3  2.8  0.08    DMI,5 kg/d  7.84  7.46  7.54  0.046  0.002    ADG,5 kg  1.35  1.31  1.31  0.017  0.11    G:F  0.172  0.176  0.173  0.0015  0.25   Carcass                   HCW,5 kg  333.6  329.6  329.7  2.05  0.19    ADG,5,6 kg  1.05  1.03  1.02  0.013  0.22    G:F5,6  0.134  0.138  0.136  0.0011  0.09  Mortality, %  0.68  0.34  0.67  0.37  0.78  Tabular NEg,7 Mcal/kg   1.53  1.58  1.58  —  —  Performance NEg,7 Mcal/kg  1.42a  1.47b  1.45a  0.008  0.01  Dressing percentage  65  65.1  65  0.13  0.82  USDA yield grade, %                  1  4.46  4.08  3.91  2  0.97   2  31.8  36  34.8  3.3  0.65   3  55.4  55.9  55.8  4.5  1   45  7.88  4.1  5.51  1.4  0.23  USDA quality grade, %                  Prime  1.72  1.73  2.7  1.3  0.76   Choice5  71.9  68.2  66.2  2.3  0.15   Choice + Prime  73.6  69.9  68.9  2.9  0.4   Select  26  30.1  30.7  2.9  0.36  Item  Dietary treatment1  SEM  P-value  CON  7.5WC  15WC  DOF2  167  167  167  —  —  DOR3  150  142  142  —  —  Performance                  Live                   Initial BW, kg  287.6  287.6  288.9  0.92  0.54    Final BW,4,5 kg  513.2  506.3  507.3  2.8  0.08    DMI,5 kg/d  7.84  7.46  7.54  0.046  0.002    ADG,5 kg  1.35  1.31  1.31  0.017  0.11    G:F  0.172  0.176  0.173  0.0015  0.25   Carcass                   HCW,5 kg  333.6  329.6  329.7  2.05  0.19    ADG,5,6 kg  1.05  1.03  1.02  0.013  0.22    G:F5,6  0.134  0.138  0.136  0.0011  0.09  Mortality, %  0.68  0.34  0.67  0.37  0.78  Tabular NEg,7 Mcal/kg   1.53  1.58  1.58  —  —  Performance NEg,7 Mcal/kg  1.42a  1.47b  1.45a  0.008  0.01  Dressing percentage  65  65.1  65  0.13  0.82  USDA yield grade, %                  1  4.46  4.08  3.91  2  0.97   2  31.8  36  34.8  3.3  0.65   3  55.4  55.9  55.8  4.5  1   45  7.88  4.1  5.51  1.4  0.23  USDA quality grade, %                  Prime  1.72  1.73  2.7  1.3  0.76   Choice5  71.9  68.2  66.2  2.3  0.15   Choice + Prime  73.6  69.9  68.9  2.9  0.4   Select  26  30.1  30.7  2.9  0.36  a,bMeans within trial and performance measure without a common superscript differ (P < 0.05). 1CON = roughage diet; 7.5WC = no roughage diet containing 7.5% of diet DM as whole corn; 15WC = no roughage diet containing 15% of diet DM as whole corn. 2DOF = average days on feed. 3DOR = days on experimental diet. 44% pencil shrink applied to final BW. 5Roughage vs. whole corn diets (P < 0.10). 6Carcass performance calculated using initial carcass weight (initial BW × 55%; MacDonald et al., 2007) and HCW. 7Tabular NEg computed using tabular ingredient energy values reported in the NRC (1996); performance-based NEg computed from DMI and BW data with a 4% shrink applied (NRC, 1996); equivalent BW was assumed to be 591 kg. View Large Table 6. Effect of dietary treatment on HCW, dressing percentage, and carcass performance for trials 1 to 41 Item  Trial  1  2  3  4  HCW, kg               CON  337.7b  339.2a  329  338.9   NR  329.4a  340.6a  322.1  334   COMB  332.4ab  345.0b  —  —   SEM  2.7  1.6  2.5  1.2   P-value  0.04  0.08  0.002  0.008  Dressing percentage              CON  64.5  62.3b  66.2  65.8   NR  64.5  61.9a  66.2  66.2   COMB  64.9  62.1ab  —  —   SEM  0.18  0.12  0.18  0.15   P-value  0.28  0.08  0.64  0.05  Carcass ADG,2 kg              CON  1.06b  1.01  0.99  1.11   NR  1.01a  1.01  0.95  1.08   COMB  1.02a  1.03  —  —   SEM  0.01  0.02  0.02  0.01   P-value  0.002  0.27  0.001  0.001  Carcass G:F2              CON  0.125b  0.11b  0.124  0.136   NR  0.129a  0.113a  0.127  0.138   COMB  0.126b  0.109b  —  —   SEM  0.0008  0.001  0.0015  0.0011   P-value  0.02  0.06  0.01  0.1  Item  Trial  1  2  3  4  HCW, kg               CON  337.7b  339.2a  329  338.9   NR  329.4a  340.6a  322.1  334   COMB  332.4ab  345.0b  —  —   SEM  2.7  1.6  2.5  1.2   P-value  0.04  0.08  0.002  0.008  Dressing percentage              CON  64.5  62.3b  66.2  65.8   NR  64.5  61.9a  66.2  66.2   COMB  64.9  62.1ab  —  —   SEM  0.18  0.12  0.18  0.15   P-value  0.28  0.08  0.64  0.05  Carcass ADG,2 kg              CON  1.06b  1.01  0.99  1.11   NR  1.01a  1.01  0.95  1.08   COMB  1.02a  1.03  —  —   SEM  0.01  0.02  0.02  0.01   P-value  0.002  0.27  0.001  0.001  Carcass G:F2              CON  0.125b  0.11b  0.124  0.136   NR  0.129a  0.113a  0.127  0.138   COMB  0.126b  0.109b  —  —   SEM  0.0008  0.001  0.0015  0.0011   P-value  0.02  0.06  0.01  0.1  a,bMeans within trial and performance measure without a common superscript differ (P < 0.05). 1CON = roughage diet; NR = no roughage diet containing whole corn; COMB = steers fed CON diet followed by NR diet. 2Carcass performance calculated using initial carcass weight (initial BW × 55%; MacDonald et al., 2007) and HCW. View Large Table 6. Effect of dietary treatment on HCW, dressing percentage, and carcass performance for trials 1 to 41 Item  Trial  1  2  3  4  HCW, kg               CON  337.7b  339.2a  329  338.9   NR  329.4a  340.6a  322.1  334   COMB  332.4ab  345.0b  —  —   SEM  2.7  1.6  2.5  1.2   P-value  0.04  0.08  0.002  0.008  Dressing percentage              CON  64.5  62.3b  66.2  65.8   NR  64.5  61.9a  66.2  66.2   COMB  64.9  62.1ab  —  —   SEM  0.18  0.12  0.18  0.15   P-value  0.28  0.08  0.64  0.05  Carcass ADG,2 kg              CON  1.06b  1.01  0.99  1.11   NR  1.01a  1.01  0.95  1.08   COMB  1.02a  1.03  —  —   SEM  0.01  0.02  0.02  0.01   P-value  0.002  0.27  0.001  0.001  Carcass G:F2              CON  0.125b  0.11b  0.124  0.136   NR  0.129a  0.113a  0.127  0.138   COMB  0.126b  0.109b  —  —   SEM  0.0008  0.001  0.0015  0.0011   P-value  0.02  0.06  0.01  0.1  Item  Trial  1  2  3  4  HCW, kg               CON  337.7b  339.2a  329  338.9   NR  329.4a  340.6a  322.1  334   COMB  332.4ab  345.0b  —  —   SEM  2.7  1.6  2.5  1.2   P-value  0.04  0.08  0.002  0.008  Dressing percentage              CON  64.5  62.3b  66.2  65.8   NR  64.5  61.9a  66.2  66.2   COMB  64.9  62.1ab  —  —   SEM  0.18  0.12  0.18  0.15   P-value  0.28  0.08  0.64  0.05  Carcass ADG,2 kg              CON  1.06b  1.01  0.99  1.11   NR  1.01a  1.01  0.95  1.08   COMB  1.02a  1.03  —  —   SEM  0.01  0.02  0.02  0.01   P-value  0.002  0.27  0.001  0.001  Carcass G:F2              CON  0.125b  0.11b  0.124  0.136   NR  0.129a  0.113a  0.127  0.138   COMB  0.126b  0.109b  —  —   SEM  0.0008  0.001  0.0015  0.0011   P-value  0.02  0.06  0.01  0.1  a,bMeans within trial and performance measure without a common superscript differ (P < 0.05). 1CON = roughage diet; NR = no roughage diet containing whole corn; COMB = steers fed CON diet followed by NR diet. 2Carcass performance calculated using initial carcass weight (initial BW × 55%; MacDonald et al., 2007) and HCW. View Large Table 7. Mortality and estimated NEg content of diets in trials 1 to 41 Item  Trial  1  2  3  4  Mortality, %               CON  0  0.66  0.23  0.27   NR  0.61  1.26  0.24  0   COMB  0  0  —  —   SEM  0.2  0.55  0.16  0.13   P-value  0.13  0.39  0.99  0.17  Tabular NEg,2 Mcal/kg              CON  1.48  1.53  1.53  1.55   NR  1.57  1.56  1.61  1.63  Performance-based NEg,2 Mcal/kg             CON  1.35a  1.28a  1.38  1.28   NR  1.39b  1.34b  1.41  1.29   COMB  1.35a  1.29a  —  —   SEM  0.013  0.011  0.008  0.011   P-value  0.02  0.001  0.002  0.22  Item  Trial  1  2  3  4  Mortality, %               CON  0  0.66  0.23  0.27   NR  0.61  1.26  0.24  0   COMB  0  0  —  —   SEM  0.2  0.55  0.16  0.13   P-value  0.13  0.39  0.99  0.17  Tabular NEg,2 Mcal/kg              CON  1.48  1.53  1.53  1.55   NR  1.57  1.56  1.61  1.63  Performance-based NEg,2 Mcal/kg             CON  1.35a  1.28a  1.38  1.28   NR  1.39b  1.34b  1.41  1.29   COMB  1.35a  1.29a  —  —   SEM  0.013  0.011  0.008  0.011   P-value  0.02  0.001  0.002  0.22  a,bMeans within trial and net energy measure without a common superscript differ (P < 0.05). 1CON = roughage diet; NR = no roughage diet containing whole corn; COMB = steers fed CON diet followed by NR diet. 2Tabular NEg computed using tabular ingredient energy values reported in the NRC (1996); performance-based NEg computed from DMI and equivalent BW data with a 4% shrink applied (NRC, 1996); equivalent BW was assumed to be 591 kg. View Large Table 7. Mortality and estimated NEg content of diets in trials 1 to 41 Item  Trial  1  2  3  4  Mortality, %               CON  0  0.66  0.23  0.27   NR  0.61  1.26  0.24  0   COMB  0  0  —  —   SEM  0.2  0.55  0.16  0.13   P-value  0.13  0.39  0.99  0.17  Tabular NEg,2 Mcal/kg              CON  1.48  1.53  1.53  1.55   NR  1.57  1.56  1.61  1.63  Performance-based NEg,2 Mcal/kg             CON  1.35a  1.28a  1.38  1.28   NR  1.39b  1.34b  1.41  1.29   COMB  1.35a  1.29a  —  —   SEM  0.013  0.011  0.008  0.011   P-value  0.02  0.001  0.002  0.22  Item  Trial  1  2  3  4  Mortality, %               CON  0  0.66  0.23  0.27   NR  0.61  1.26  0.24  0   COMB  0  0  —  —   SEM  0.2  0.55  0.16  0.13   P-value  0.13  0.39  0.99  0.17  Tabular NEg,2 Mcal/kg              CON  1.48  1.53  1.53  1.55   NR  1.57  1.56  1.61  1.63  Performance-based NEg,2 Mcal/kg             CON  1.35a  1.28a  1.38  1.28   NR  1.39b  1.34b  1.41  1.29   COMB  1.35a  1.29a  —  —   SEM  0.013  0.011  0.008  0.011   P-value  0.02  0.001  0.002  0.22  a,bMeans within trial and net energy measure without a common superscript differ (P < 0.05). 1CON = roughage diet; NR = no roughage diet containing whole corn; COMB = steers fed CON diet followed by NR diet. 2Tabular NEg computed using tabular ingredient energy values reported in the NRC (1996); performance-based NEg computed from DMI and equivalent BW data with a 4% shrink applied (NRC, 1996); equivalent BW was assumed to be 591 kg. View Large Because diets containing no roughage, but without the addition of whole corn, were not tested, confounding existed to the extent that it was not possible to attribute effects solely to the removal of roughage, the addition of whole corn, or to the resulting changes in other dietary ingredients. Feeding finishing diets containing whole corn without roughage reduced final BW, ADG, and DMI by approximately 1.5, 3.7, and 5.7%, respectively, but G:F was improved an average of 3.5% relative to diets containing roughage. Vance et al. (1972) also observed that feed efficiency was improved for all-concentrate diets regardless of whether corn was fed whole or crimped. Cole et al. (1976) fed whole corn diets containing 0, 7, 14, or 21% roughage with the roughage being cottonseed hulls, and the study noted that steers fed the whole corn diet with no roughage consumed 15 to 25% less DM. Utley and McCormick (1980) observed that yearling steers fed whole corn, no-roughage diets had 20% less DMI than yearling steers fed whole corn diets with Bermuda grass pellets. Traxler et al. (1995) fed Holstein steers whole corn diet with no-roughage and observed no difference in ADG even though DMI was decreased 13% and feed efficiency (DMI/ADG) was improved by 15% when compared with diets containing roughage or roughage pellets. Steer calves fed diets containing 70, 85, or 100% concentrate from whole unprocessed, high-moisture corn had similar overall DMI and ADG (Loerch and Fluharty, 1998) but had a 7 to 9.4% improvement in feed efficiency (DMI/ADG) for steers finished on the 100% concentrate diet compared with steers finished on the 85% concentrate diet. Therefore, observations from trials 1 to 6 in the current study tend to match results from published small pen research trials. Performance-based NEg was 0.8 to 4.7% greater for steers finished on NR compared with CON diets. Greater NEg content of whole corn diets without roughage presumably is manifested through an increased supply of nonstructural carbohydrates for growth. To explore this possibility, starch intake of the dietary treatments fed in our trials was calculated using starch contents of 72.2, 70.8, and 67.2% for corn, milo, and wheat, respectively (DM basis; Kellems and Church, 1998). High-moisture corn was assumed to contain 65% starch, and sorghum silage was assumed to contain 31% starch (DM basis). Contributions of starch from other dietary ingredients were considered to be negligible and were not considered in the calculations. Using these estimated levels, starch intake was 3.4% greater for steers fed NR diets compared with those fed CON diets (4.90 vs. 4.74 kg/d, respectively). Although whole corn resists enzymatic activity in the digestive tract (Rust, 1983; Owens et al., 1986; Beauchemin et al., 1994; McAllister et al., 1994) unless it is chewed, the increase in total dietary starch content for NR treatments presumably would largely offset this decrease in starch digestibility. Using reported digestibility coefficients (Owens et al., 1986; Huntington, 1997), estimated starch digested in the total digestive tract was 2.5% greater for the NR treatments compared with the CON treatments (4.71 vs. 4.59 kg/d, respectively). The increased metabolite load as a result of a greater supply of fermentable starch probably induced a stronger feedback stimulus to satiety centers in the brain to reduce feed intake (Forbes, 2003). By definition, metabolites consist of any compound liberated during metabolism (Kellems and Church, 1998); however, within the context of starch utilization in ruminants, such metabolites would consist of glucose, VFA, and lactate. These metabolites involved not only in chemostatic regulation of feed intake mentioned previously, but also in the initiation of ruminal acidosis (Owens et al., 1998). The association between ruminal acidosis and feed intake is critical. One obvious response observed in feedlot cattle to subacute ruminal acidosis is a reduction in feed intake (Britton and Stock, 1987). In this study, DMI was less when the whole corn-no roughage diet was fed. Including roughage in high concentrate diets reduces the incidence of ruminal acidosis (Wise et al., 1968; Owens et al., 1998). Although ruminal acidosis may have been more prevalent with the NR diet than CON diets, the fact that BW gain decreased by only 3.7%, and G:F was improved, indicates that steers must have adapted to diets without roughage. Greater DMI for diets containing roughage also could be the result of increased saliva flow and ruminal motility (Nagaraja and Lechtenberg, 2007) associated with feeding of roughage. Both should increase ruminal outflow and postruminal starch supply but decrease the time for ruminal digestion of fiber and coarser concentrates. This also could explain the decreased diet NEg for diets containing roughage. By difference, the NEg value of whole corn in these trials ranged from 0.87 to 1.46 Mcal of NEg/kg, all being less than the NRC (1996) estimate of 1.55 Mcal of NEg/kg. However, NEg of whole corn increased linearly (R2 = 0.79; data not shown) with days on feed, a phenomenon that might be explained by decreased DMI or lighter BW of cattle earlier in these feeding studies. Although younger cattle (Owens et al., 1997) tend to chew and ruminate more thoroughly and thereby digest starch from whole corn more extensively than older cattle, initial BW was elevated in all trials and was not related to observed NE values. This discrepancy also may reflect other factors depressing value of the CON diet, e.g., suboptimal (e.g., moderately dry) high-moisture corn, coarse rolling of dry corn grain in the diet, or coarseness of flakes from milo or wheat grains. Dry matter intake as a percentage of BW for steers within each trial is plotted against the concentration of NDF in the diet from roughage as calculated from dietary ingredient analyses provided by NRC (1996). On the average (Figure 1), daily DMI of NR diets was 1.859% of mean BW, which is similar to the value of 1.856 estimated by Galyean and Defoor (2003). Across all 6 trials, as the NDF from roughage increased, DMI increased at a rate equal to 0.0199 (±0.0012)% for each 1% increase in NDF from roughage. This slope is less than that of 0.0275 proposed by Galyean and Defoor (2003). This slight difference in slope may be due to differences in the source or in processing of grain and roughage among the various trials and to presence of whole corn in all of our diets that did not contain added roughage. Figure 1. View largeDownload slide Observed DMI at various dietary roughage NDF concentrations (DMI = 1.906 + 0.0199 ± 0.0012 NDF; P < 0.05). Figure 1. View largeDownload slide Observed DMI at various dietary roughage NDF concentrations (DMI = 1.906 + 0.0199 ± 0.0012 NDF; P < 0.05). Yield grade (USDA) was less (P = 0.05) for NR compared with CON in trial 1, and more USDA Prime and Choice carcasses were noted (P < 0.02) for CON vs. NR in trial 3 (Tables 8 and 9). Other than this, differences observed for USDA yield and quality grade associated with diet were subtle. These results imply feeding diets containing whole corn without roughage had limited effect on carcass quality. Vance et al. (1972) fed Hereford steer calves whole or crimped corn diets with 0, 2.3, 4.5, 6.8, 9.1, and 11.3 kg/d of corn silage, and the study noted that feeding 4.5 kg/d of corn silage produced carcasses with the greatest marbling score and USDA quality grade. In other trials with whole corn-no added roughage diets, no effects on carcass characteristics have been reported (Wise et al., 1965; Utley and McCormick, 1980; Traxler et al., 1995). Effects of dietary energy density on carcass characteristics have not been widely detected (Krehbiel et al., 2006), perhaps due to the small numbers of animals used in small pen trials (Turgeon and Koers, 1997). Table 8. Effect of dietary treatment on USDA yield grade for trials 1, 3, and 41 Item  Trial  1  3  4  USDA yield grade 1, %          CON  11.5a  2.61  2.49   NR  14.0b  4.13  4.06   COMB  19.8c  —  —   SEM  0.93  0.79  0.66   P-value  0.002  0.21  0.05  USDA yield grade 2, %          CON  55.5a  36.3  37.6   NR  60.8b  41.9  42.4   COMB  64.2b  —  —   SEM  2.08  2.76  2.68   P-value  0.02  0.09  0.12  USDA yield grade 3, %          CON  30.0b  56.8  50.9   NR  19.1a  51.4  48.4   COMB  21.2a  —  —   SEM  2.1  2.43  2.18   P-value  0.02  0.15  0.43  USDA yield grade 4, %          CON  3.06b  4.18  8.4   NR  0.3a  2.51  4.77   COMB  0.58a  —  —   SEM  0.78  1.03  1.18   P-value  0.05  0.12  0.04  Item  Trial  1  3  4  USDA yield grade 1, %          CON  11.5a  2.61  2.49   NR  14.0b  4.13  4.06   COMB  19.8c  —  —   SEM  0.93  0.79  0.66   P-value  0.002  0.21  0.05  USDA yield grade 2, %          CON  55.5a  36.3  37.6   NR  60.8b  41.9  42.4   COMB  64.2b  —  —   SEM  2.08  2.76  2.68   P-value  0.02  0.09  0.12  USDA yield grade 3, %          CON  30.0b  56.8  50.9   NR  19.1a  51.4  48.4   COMB  21.2a  —  —   SEM  2.1  2.43  2.18   P-value  0.02  0.15  0.43  USDA yield grade 4, %          CON  3.06b  4.18  8.4   NR  0.3a  2.51  4.77   COMB  0.58a  —  —   SEM  0.78  1.03  1.18   P-value  0.05  0.12  0.04  a–cMeans within trial and carcass measure without a common superscript differ (P < 0.05). 1CON = roughage diet; NR = no roughage diet containing whole corn; COMB = steers fed CON diet followed by NR diet. View Large Table 8. Effect of dietary treatment on USDA yield grade for trials 1, 3, and 41 Item  Trial  1  3  4  USDA yield grade 1, %          CON  11.5a  2.61  2.49   NR  14.0b  4.13  4.06   COMB  19.8c  —  —   SEM  0.93  0.79  0.66   P-value  0.002  0.21  0.05  USDA yield grade 2, %          CON  55.5a  36.3  37.6   NR  60.8b  41.9  42.4   COMB  64.2b  —  —   SEM  2.08  2.76  2.68   P-value  0.02  0.09  0.12  USDA yield grade 3, %          CON  30.0b  56.8  50.9   NR  19.1a  51.4  48.4   COMB  21.2a  —  —   SEM  2.1  2.43  2.18   P-value  0.02  0.15  0.43  USDA yield grade 4, %          CON  3.06b  4.18  8.4   NR  0.3a  2.51  4.77   COMB  0.58a  —  —   SEM  0.78  1.03  1.18   P-value  0.05  0.12  0.04  Item  Trial  1  3  4  USDA yield grade 1, %          CON  11.5a  2.61  2.49   NR  14.0b  4.13  4.06   COMB  19.8c  —  —   SEM  0.93  0.79  0.66   P-value  0.002  0.21  0.05  USDA yield grade 2, %          CON  55.5a  36.3  37.6   NR  60.8b  41.9  42.4   COMB  64.2b  —  —   SEM  2.08  2.76  2.68   P-value  0.02  0.09  0.12  USDA yield grade 3, %          CON  30.0b  56.8  50.9   NR  19.1a  51.4  48.4   COMB  21.2a  —  —   SEM  2.1  2.43  2.18   P-value  0.02  0.15  0.43  USDA yield grade 4, %          CON  3.06b  4.18  8.4   NR  0.3a  2.51  4.77   COMB  0.58a  —  —   SEM  0.78  1.03  1.18   P-value  0.05  0.12  0.04  a–cMeans within trial and carcass measure without a common superscript differ (P < 0.05). 1CON = roughage diet; NR = no roughage diet containing whole corn; COMB = steers fed CON diet followed by NR diet. View Large Table 9. Effect of dietary treatment on USDA quality grade for trials 1 to 41 Item  Trial  1  2  3  4  USDA Prime, %              CON  0  3.29  0.82  0.14   NR  0.29  2.09  0.24  0.14   COMB  0  2.15  —  —   SEM  0.17  1.4  0.25  0.14   P-value  0.42  0.81  0.13  0.99  USDA Choice, %              CON  45.4  79.5  51.4  53.5   NR  41.1  85.2  46.3  54.2   COMB  40.4  87.2  —  —   SEM  4.4  4.2  2.4  3.4   P-value  0.62  0.44  0.06  0.8  USDA Choice + Prime, %             CON  45.4  82.8  52.1  53.6   NR  41.1  87.3  46.4  54.4   COMB  40.7  88.4  —  —   SEM  4.3  3.1  2.4  3.5   P-value  0.64  0.36  0.02  0.8  USDA Select, %              CON  54.3  17.2  47.7  46.4   NR  58.9  12.8  53.4  45.6   COMB  58.7  10.6  —  —   SEM  4.2  3.1  2.4  3.5   P-value  0.64  0.36  0.02  0.8  Item  Trial  1  2  3  4  USDA Prime, %              CON  0  3.29  0.82  0.14   NR  0.29  2.09  0.24  0.14   COMB  0  2.15  —  —   SEM  0.17  1.4  0.25  0.14   P-value  0.42  0.81  0.13  0.99  USDA Choice, %              CON  45.4  79.5  51.4  53.5   NR  41.1  85.2  46.3  54.2   COMB  40.4  87.2  —  —   SEM  4.4  4.2  2.4  3.4   P-value  0.62  0.44  0.06  0.8  USDA Choice + Prime, %             CON  45.4  82.8  52.1  53.6   NR  41.1  87.3  46.4  54.4   COMB  40.7  88.4  —  —   SEM  4.3  3.1  2.4  3.5   P-value  0.64  0.36  0.02  0.8  USDA Select, %              CON  54.3  17.2  47.7  46.4   NR  58.9  12.8  53.4  45.6   COMB  58.7  10.6  —  —   SEM  4.2  3.1  2.4  3.5   P-value  0.64  0.36  0.02  0.8  1CON = roughage diet; NR = no roughage diet containing whole corn; COMB = steers fed CON diet followed by NR diet. View Large Table 9. Effect of dietary treatment on USDA quality grade for trials 1 to 41 Item  Trial  1  2  3  4  USDA Prime, %              CON  0  3.29  0.82  0.14   NR  0.29  2.09  0.24  0.14   COMB  0  2.15  —  —   SEM  0.17  1.4  0.25  0.14   P-value  0.42  0.81  0.13  0.99  USDA Choice, %              CON  45.4  79.5  51.4  53.5   NR  41.1  85.2  46.3  54.2   COMB  40.4  87.2  —  —   SEM  4.4  4.2  2.4  3.4   P-value  0.62  0.44  0.06  0.8  USDA Choice + Prime, %             CON  45.4  82.8  52.1  53.6   NR  41.1  87.3  46.4  54.4   COMB  40.7  88.4  —  —   SEM  4.3  3.1  2.4  3.5   P-value  0.64  0.36  0.02  0.8  USDA Select, %              CON  54.3  17.2  47.7  46.4   NR  58.9  12.8  53.4  45.6   COMB  58.7  10.6  —  —   SEM  4.2  3.1  2.4  3.5   P-value  0.64  0.36  0.02  0.8  Item  Trial  1  2  3  4  USDA Prime, %              CON  0  3.29  0.82  0.14   NR  0.29  2.09  0.24  0.14   COMB  0  2.15  —  —   SEM  0.17  1.4  0.25  0.14   P-value  0.42  0.81  0.13  0.99  USDA Choice, %              CON  45.4  79.5  51.4  53.5   NR  41.1  85.2  46.3  54.2   COMB  40.4  87.2  —  —   SEM  4.4  4.2  2.4  3.4   P-value  0.62  0.44  0.06  0.8  USDA Choice + Prime, %             CON  45.4  82.8  52.1  53.6   NR  41.1  87.3  46.4  54.4   COMB  40.7  88.4  —  —   SEM  4.3  3.1  2.4  3.5   P-value  0.64  0.36  0.02  0.8  USDA Select, %              CON  54.3  17.2  47.7  46.4   NR  58.9  12.8  53.4  45.6   COMB  58.7  10.6  —  —   SEM  4.2  3.1  2.4  3.5   P-value  0.64  0.36  0.02  0.8  1CON = roughage diet; NR = no roughage diet containing whole corn; COMB = steers fed CON diet followed by NR diet. View Large An interaction between dietary treatment and days on feed was detected in trial 5 (Table 10). In agreement with the other trials, final BW and HCW were greater (P < 0.05) for CON than NR, but this advantage tended to diminish as days on feed increased. Dry matter intake and ADG also were greater (P < 0.05) for CON than NR, but the magnitude of difference between CON and NR treatments decreased as days on feed increased. From 155 to 169 d on feed, DMI and ADG were increased for NR treatments such that G:F tended to be improved (0.1584 vs. 0.1589, respectively). This stands in contrast with G:F for CON-fed steers, which became poorer during this same time interval (0.158 vs. 0.1524, respectively). As expected, feed intake and growth performance decreased as days on feed increased for steers fed the CON vs. NR diets (Van Koevering et al., 1995; Sissom et al., 2007; Winterholler et al., 2007), but why feed intake by steers fed NR tended to increase for groups fed longer is not readily apparent. Diet NEg calculated from feedlot performance was greater (P < 0.001) for NR, with the magnitude of improvement relative to CON treatments increasing with increasing days on feed. Interactions between days on feed and dietary treatment were not detected for carcass data and carcass performance. Dressing percentage and the number of USDA yield grade 3 and 4 carcasses increased linearly (P < 0.08) with more days on feed, whereas the number of USDA yield grade 2 carcasses and carcasses grading USDA Choice decreased (P < 0.09) with increasing days on feed. No differences were noted for percentage of USDA Prime carcasses. No explanation is readily apparent for this decrease in quality grade. Slaughter dates for endpoints corresponding to 134, 155, and 169 d on feed were March 1, March 22, and April 5, 1990, respectively. Table 10. Effect of dietary treatment and feeding duration on growth performance and carcass characteristics for trial 5 Item  Days on feed  SEM  P-value1  134  155  169  CON2  NR2  CON  NR  CON  NR  DIET  DOF  INT  DOR3  119  119  140  131  164  145  —  —  —  —  Performance                                 Live                                  Initial BW, kg  341  338  337  335  336  337  1.2  0.25  0.33  0.48    Final BW,4 kg  513  493a  534  515a  542  538  3.3  0.001  0.01  0.02    DMI, kg/d  8.3  7.48a  8.04  7.32a  8  7.47a  0.06  0.001  0.07  0.03    ADG, kg  1.29  1.16a  1.27  1.16a  1.22  1.19a  0.02  0.001  0.64  0.002    G:F  0.155  0.155  0.158  0.159  0.152  0.159a  0.0015  0.003  0.29  0.002   Carcass5                                  HCW, kg  332  321  350  338  358  354  2.5  0.002  0.01b  0.16    ADG, kg  1.08  1  1.06  0.99  1.02  1  0.012  0.001  0.11b  0.09    G:F  0.13  0.135  0.132  0.135  0.128  0.134  0.0011  0.001  0.18  0.29  Mortality, %  0.97  0  0.43  0  0.43  0  0.47  0.16  0.81  0.81  Tabular NEg,6 Mcal/kg  1.5  1.58  1.5  1.58  1.5  1.58  —  —  —  —  Performance NEg,6 Mcal/kg  1.37  1.39a  1.41  1.44a  1.38  1.46a  0.01  0.001  0.06  0.001  Dressing percentage  64.8  65  65.4  65.6  66  65.9  0.21  0.54  0.01b  0.75  USDA yield grade, %                                 1  2.62  3.96  2.62  4.4  2.58  4  1.6  0.28  0.99  0.99   2  41.4  53.3  32.7  38.8  34.7  33.5  3.1  0.07  0.01b  0.18   3  55.2  41.9  60.3  54.2  55  58.1  3.2  0.08  0.06b  0.11   4  0.87  0.88  4.4  2.64  7.3  4  1.5  0.13  0.08b  0.42  USDA quality grade, %                                 Prime  0  0.44  2.63  2.19  1.71  1.79  0.9  0.96  0.19  0.81   Choice + Prime  83.4  78.4  81.3  81.5  76.4  74.6  2.4  0.23  0.14  0.48   Choice  83.4  78  78.6  79.3  74.7  72.8  2.45  0.27  0.09b  0.44   Select  16.1  21.2  18.8  18.1  23.6  25.5  2.5  0.28  0.11  0.45  Item  Days on feed  SEM  P-value1  134  155  169  CON2  NR2  CON  NR  CON  NR  DIET  DOF  INT  DOR3  119  119  140  131  164  145  —  —  —  —  Performance                                 Live                                  Initial BW, kg  341  338  337  335  336  337  1.2  0.25  0.33  0.48    Final BW,4 kg  513  493a  534  515a  542  538  3.3  0.001  0.01  0.02    DMI, kg/d  8.3  7.48a  8.04  7.32a  8  7.47a  0.06  0.001  0.07  0.03    ADG, kg  1.29  1.16a  1.27  1.16a  1.22  1.19a  0.02  0.001  0.64  0.002    G:F  0.155  0.155  0.158  0.159  0.152  0.159a  0.0015  0.003  0.29  0.002   Carcass5                                  HCW, kg  332  321  350  338  358  354  2.5  0.002  0.01b  0.16    ADG, kg  1.08  1  1.06  0.99  1.02  1  0.012  0.001  0.11b  0.09    G:F  0.13  0.135  0.132  0.135  0.128  0.134  0.0011  0.001  0.18  0.29  Mortality, %  0.97  0  0.43  0  0.43  0  0.47  0.16  0.81  0.81  Tabular NEg,6 Mcal/kg  1.5  1.58  1.5  1.58  1.5  1.58  —  —  —  —  Performance NEg,6 Mcal/kg  1.37  1.39a  1.41  1.44a  1.38  1.46a  0.01  0.001  0.06  0.001  Dressing percentage  64.8  65  65.4  65.6  66  65.9  0.21  0.54  0.01b  0.75  USDA yield grade, %                                 1  2.62  3.96  2.62  4.4  2.58  4  1.6  0.28  0.99  0.99   2  41.4  53.3  32.7  38.8  34.7  33.5  3.1  0.07  0.01b  0.18   3  55.2  41.9  60.3  54.2  55  58.1  3.2  0.08  0.06b  0.11   4  0.87  0.88  4.4  2.64  7.3  4  1.5  0.13  0.08b  0.42  USDA quality grade, %                                 Prime  0  0.44  2.63  2.19  1.71  1.79  0.9  0.96  0.19  0.81   Choice + Prime  83.4  78.4  81.3  81.5  76.4  74.6  2.4  0.23  0.14  0.48   Choice  83.4  78  78.6  79.3  74.7  72.8  2.45  0.27  0.09b  0.44   Select  16.1  21.2  18.8  18.1  23.6  25.5  2.5  0.28  0.11  0.45  aNR differs (P < 0.05) from CON within a given DOF subclass. bLinear effect of DOF (P < 0.05). 1DIET = main effect of dietary treatment; DOF = main effect of days on feed; INT = interaction term. 2CON = roughage diet; NR = no roughage diet containing whole corn. 3DOR = days on experimental diet. 44% pencil shrink applied to final BW. 5Carcass performance calculated using initial carcass weight (initial BW × 55%; MacDonald et al., 2007) and HCW. 6Tabular NEg computed using tabular ingredient energy values reported in the NRC (1996); performance-based NEg computed from DMI and BW data with a 4% shrink applied (NRC, 1996); equivalent BW was assumed to be 591 kg. View Large Table 10. Effect of dietary treatment and feeding duration on growth performance and carcass characteristics for trial 5 Item  Days on feed  SEM  P-value1  134  155  169  CON2  NR2  CON  NR  CON  NR  DIET  DOF  INT  DOR3  119  119  140  131  164  145  —  —  —  —  Performance                                 Live                                  Initial BW, kg  341  338  337  335  336  337  1.2  0.25  0.33  0.48    Final BW,4 kg  513  493a  534  515a  542  538  3.3  0.001  0.01  0.02    DMI, kg/d  8.3  7.48a  8.04  7.32a  8  7.47a  0.06  0.001  0.07  0.03    ADG, kg  1.29  1.16a  1.27  1.16a  1.22  1.19a  0.02  0.001  0.64  0.002    G:F  0.155  0.155  0.158  0.159  0.152  0.159a  0.0015  0.003  0.29  0.002   Carcass5                                  HCW, kg  332  321  350  338  358  354  2.5  0.002  0.01b  0.16    ADG, kg  1.08  1  1.06  0.99  1.02  1  0.012  0.001  0.11b  0.09    G:F  0.13  0.135  0.132  0.135  0.128  0.134  0.0011  0.001  0.18  0.29  Mortality, %  0.97  0  0.43  0  0.43  0  0.47  0.16  0.81  0.81  Tabular NEg,6 Mcal/kg  1.5  1.58  1.5  1.58  1.5  1.58  —  —  —  —  Performance NEg,6 Mcal/kg  1.37  1.39a  1.41  1.44a  1.38  1.46a  0.01  0.001  0.06  0.001  Dressing percentage  64.8  65  65.4  65.6  66  65.9  0.21  0.54  0.01b  0.75  USDA yield grade, %                                 1  2.62  3.96  2.62  4.4  2.58  4  1.6  0.28  0.99  0.99   2  41.4  53.3  32.7  38.8  34.7  33.5  3.1  0.07  0.01b  0.18   3  55.2  41.9  60.3  54.2  55  58.1  3.2  0.08  0.06b  0.11   4  0.87  0.88  4.4  2.64  7.3  4  1.5  0.13  0.08b  0.42  USDA quality grade, %                                 Prime  0  0.44  2.63  2.19  1.71  1.79  0.9  0.96  0.19  0.81   Choice + Prime  83.4  78.4  81.3  81.5  76.4  74.6  2.4  0.23  0.14  0.48   Choice  83.4  78  78.6  79.3  74.7  72.8  2.45  0.27  0.09b  0.44   Select  16.1  21.2  18.8  18.1  23.6  25.5  2.5  0.28  0.11  0.45  Item  Days on feed  SEM  P-value1  134  155  169  CON2  NR2  CON  NR  CON  NR  DIET  DOF  INT  DOR3  119  119  140  131  164  145  —  —  —  —  Performance                                 Live                                  Initial BW, kg  341  338  337  335  336  337  1.2  0.25  0.33  0.48    Final BW,4 kg  513  493a  534  515a  542  538  3.3  0.001  0.01  0.02    DMI, kg/d  8.3  7.48a  8.04  7.32a  8  7.47a  0.06  0.001  0.07  0.03    ADG, kg  1.29  1.16a  1.27  1.16a  1.22  1.19a  0.02  0.001  0.64  0.002    G:F  0.155  0.155  0.158  0.159  0.152  0.159a  0.0015  0.003  0.29  0.002   Carcass5                                  HCW, kg  332  321  350  338  358  354  2.5  0.002  0.01b  0.16    ADG, kg  1.08  1  1.06  0.99  1.02  1  0.012  0.001  0.11b  0.09    G:F  0.13  0.135  0.132  0.135  0.128  0.134  0.0011  0.001  0.18  0.29  Mortality, %  0.97  0  0.43  0  0.43  0  0.47  0.16  0.81  0.81  Tabular NEg,6 Mcal/kg  1.5  1.58  1.5  1.58  1.5  1.58  —  —  —  —  Performance NEg,6 Mcal/kg  1.37  1.39a  1.41  1.44a  1.38  1.46a  0.01  0.001  0.06  0.001  Dressing percentage  64.8  65  65.4  65.6  66  65.9  0.21  0.54  0.01b  0.75  USDA yield grade, %                                 1  2.62  3.96  2.62  4.4  2.58  4  1.6  0.28  0.99  0.99   2  41.4  53.3  32.7  38.8  34.7  33.5  3.1  0.07  0.01b  0.18   3  55.2  41.9  60.3  54.2  55  58.1  3.2  0.08  0.06b  0.11   4  0.87  0.88  4.4  2.64  7.3  4  1.5  0.13  0.08b  0.42  USDA quality grade, %                                 Prime  0  0.44  2.63  2.19  1.71  1.79  0.9  0.96  0.19  0.81   Choice + Prime  83.4  78.4  81.3  81.5  76.4  74.6  2.4  0.23  0.14  0.48   Choice  83.4  78  78.6  79.3  74.7  72.8  2.45  0.27  0.09b  0.44   Select  16.1  21.2  18.8  18.1  23.6  25.5  2.5  0.28  0.11  0.45  aNR differs (P < 0.05) from CON within a given DOF subclass. bLinear effect of DOF (P < 0.05). 1DIET = main effect of dietary treatment; DOF = main effect of days on feed; INT = interaction term. 2CON = roughage diet; NR = no roughage diet containing whole corn. 3DOR = days on experimental diet. 44% pencil shrink applied to final BW. 5Carcass performance calculated using initial carcass weight (initial BW × 55%; MacDonald et al., 2007) and HCW. 6Tabular NEg computed using tabular ingredient energy values reported in the NRC (1996); performance-based NEg computed from DMI and BW data with a 4% shrink applied (NRC, 1996); equivalent BW was assumed to be 591 kg. 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TI - Manipulating grain processing method and roughage level to improve feed efficiency in feedlot cattle
JO - Journal of Animal Science
DO - 10.2527/jas.2009-1859
DA - 2010-01-01
UR - https://www.deepdyve.com/lp/oxford-university-press/manipulating-grain-processing-method-and-roughage-level-to-improve-e721sYmGaL
SP - 284
EP - 295
VL - 88
IS - 1
DP - DeepDyve
ER -