TY - JOUR
AU - Kim, Sung, Woo
AB - Abstract This study was conducted to evaluate the effects of suckling intensity (litter size and lactation length) to primiparious sows on production performance during current and subsequent parities. Upon farrowing, 115 primiparous sows (farrowing weight: 222.7 ± 20.0 kg) were initially allotted to 4 treatments in a 2 × 2 factorial arrangement with 2 litter sizes: 10 and 13 piglets (LS10 vs. LS13), and 2 lactation lengths: 21 and 27 d (LL21 vs. LL27). Upon weaning, sows were rebred and those farrowed successfully (n = 66) kept 10 piglets and weaned at 21 d in the second parity. Sows were fed ad libitum during lactation in both parities. Feed intake, BW loss, backfat loss, litter size, and litter weight gain during lactation in both parities were determined. Litter weight gain in LS13 was greater (P < 0.05) than that in LS10 (54.4 vs. 47.7 kg) during the first lactation. Sows in LS13 had a greater (P < 0.05) BW loss than sows in LS10 (24.1 vs. 17.4 kg). Body weight loss was not different between LL27 and LL21. Sows in LS13 tended to have a greater (P = 0.075) removal rate than those in LS10 (47.5 vs. 32.2%). Sows in LL27 had a smaller (P < 0.05) removal rate than those in LL21 (28.0 vs. 51.7%). In the second parity, gestation BW gain in LL27 tended to be greater (P = 0.098) than that in LL21 when the previous litter size was 10 piglets (56.1 vs. 33.2 kg). Litter performance and feed intake of sows were not affected by previous litter size, lactation length, and their interaction. The farrowing weight, farrowing body protein and lipid, body weight loss was not different between LS13 and LS10, whereas backfat loss in LS13 was smaller (P < 0.05) than that in LS10 during the second lactation (0.9 vs. 2.4 mm). The predicted body lipid loss in LS13 was also smaller than that in LS10 (2.3 vs. 5.3 kg) during the second lactation. Sows in LL27 had a smaller (P < 0.05) BW loss and body lipid loss during the second lactation than sows in LL21 (4.0 vs. 9.0 kg; 2.3 vs. 4.8 kg). The concentration of milk fat in LL27 was smaller (P < 0.05) than that in LL21 (7.9 vs. 9.1%). In conclusion, increasing suckling intensity to primiparous sows increased litter weight gain but increasing litter size reduced piglet ADG. Sow performance in the second lactation was not negatively affected by increasing suckling intensity of the first lactation. Interestingly, sows with an increased suckling intensity in the first lactation had reduced loss of body reserves in the second lactation. Introduction Sows require intensive nutritional management because of the continuous genetic selection on prolificacy and leaner body composition. Subsequently, sows nowadays have less body fat but need to produce a higher amount of milk to support litter growth. The primiparous sows are especially more vulnerable than the older ones because primiparous sows not only have less body reserves but also consume less feed during the lactation (Kim and Easter, 2001; NRC, 2012). Extensive body protein and lipid mobilization during the first lactation negatively affect production performance in a subsequent parity and detrimentally affect lifetime productivity of sows (Aherne et al., 1994; Boyd et al., 2000; Clowes et al., 2003a). Therefore, the recommended nutrient requirements for sows have distinct differences among different parities and farrowing body weight (Kim et al., 2001; NRC, 2012). A major question arises: do the primiparous sows require different management or does the suckling intensity of primiparous sows need to be reduced so that body reserves (protein, fat, and bone) can be conserved? Suckling intensity can affect milk production and body reserves through some planned changes in suckling frequency, litter size, lactation length, and size of piglets (Auldist et al., 1998; King, 2000; Hurley, 2001; Marshall et al., 2006). However, suckling intensity has started to change obligatorily since litter size continuously increases through genetic selection and lactation length is slowly increasing as well among these years. The number of pigs per litter in the United States increased by 2.4 pigs from 1988 to 2012 (NASS, 1994, 2014). On the other hand, lactation length is increasing due to the reduced use of antibiotic growth promoters and increased concerns in animal welfare and health at weaning. However, except for the detrimental effects, previous research also points out some beneficial effects of increasing suckling intensity on mammary growth of primiparous sows. Increasing suckling teat numbers not only results in an increased postpartum mammary growth but also increase the mammary development during the second lactation (Kim et al., 1999; Farmer et al., 2012). The reproductive performance of primiparous sows is compromised by the active growth and development of body tissues towards maturity (Whittemore, 1996). Management of suckling intensity such as litter size and lactation length affects the primiparous sow development and may further affect the sow lifetime productivity (Boyd et al., 2002; Spencer et al., 2003). Therefore, this study was conducted to evaluate the effects of suckling intensity (litter size and lactation length) of the primiparous sows on production performance during lactation in current and subsequent parities. Materials and Methods Animals and Experimental Design A protocol for the use of animals in this study was approved by North Carolina State University Animal Care and Use Committee. The experiment was conducted at a commercial sow farm (Smithfield Foods Inc., Kinston, NC). A total of 115 crossbred Large White × Landrace gilts (Smithfield Premium Genetics, Rose Hill, NC, BW of 222.7 ± 20.0 kg, approximately 350 d of age at farrowing) were initially allocated to 4 treatments in a 2 × 2 factorial arrangement with 2 litter sizes: 10 and 13 piglets (LS10 vs. LS13); and 2 lactation lengths: 21 and 27 d (LL21 vs. LL27) during the first lactation. Therefore, increased suckling intensity in the first lactation was achieved by increasing litter size and elongating lactation length. Within 24 h after farrowing, sows were allotted to 2 litter size (the first factor) groups: (1) 61 sows with litters of 9.8 ± 0.5 piglets; (2) 54 sows with litters of 13.4 ± 1.0 piglets (litter size was targeted at 14 piglets but the actual number was rather close to 13 piglets). The litter size was adjusted by cross-fostering using piglets as uniform birth weight as possible (piglets with an average weight among litters). At weaning, sows in either litter size group were further allotted to 1 of 2 subgroups with lactation length (the second factor) of 21.0 ± 1.4 or 27.0 ± 0.7 d, respectively. Subsequently, the weaning age for piglets in LL21 or LL27 was 21 or 27 d, respectively. The 4 treatments were coded as LS10-LL21, LS10-LL27, LS13-LL21, and LS13-LL27. The number of replications among treatments was different because not all sows successfully farrowed and some sows were removed from the experiment because of failure to conceive, abortion, high stillbirths, poor body condition, and locomotor problems. The number of sows or litters in the first parity was 40, 21, 30, and 24 for LS10-LL21, LS10-LL27, LS13-LL21, and LS13-LL27, respectively. Sows returned to gestation room after weaning and rebred. At day 42 postbreeding, sows were moved from individual stalls (0.61 m × 2.10 m) into the group pens with 6 sows per pen (2.2 m2 per sow). Pens had quarter stalls and were equipped with a handing nipple. In the second parity, any sows that did not come back to cycle normally (including culling, failure to conceive, anestrus, abortion) were excluded from experiment because the sows allowed for rebreeding after the pregnancy test would have an additional period to grow, which might affect the treatment effects. At day 108 of gestation in the second parity, sows were moved to farrowing crates (1.70 m × 2.30 m) again. Within 24 h after the farrowing, litter size was set to 10.1 ± 1.0 piglets and piglets were weaned at day 20.7 ± 0.6 of lactation during the second parity for all treatments. All sows during the second lactation were considered receiving the same suckling intensity. After the removal of sows that did not become pregnant or farrow, the number of sows or litters during the second lactation were 20, 18, 14, and 14 for LS10-LL21, LS10-LL27, LS13-LL21, and LS13-LL27, respectively. All sows were fed a 2-kg common diet daily during the second gestation. Sows were fed ad libitum during the entire period of lactation in both parities. The feed was corn-soybean meal-based and formulated to meet or exceed the nutrient requirements recommended by NRC (2012). During both lactations, the feed was provided daily at 0630, 1100, and 1630 h. Sows had free access to water. Collection of Sow and Piglets Performance Data Individual sows and piglets were weighed at farrowing, day 10 of lactation, and weaning in the first parity. At farrowing, day 10 of lactation, and weaning, the backfat thickness was measured twice using a digital backfat indicator (Renco lean-meter; Renco Corporation, Minneapolis, MN) with the digital backfat indicator probe placed over the last rib at 6 to 7 cm from the dorsal midline (P2 backfat). Flank-to-flank (in front of hind legs, from bottom of flank on one side over back of sow to the other flank) and heart girth (behind the front legs and in front of the first pairs of mammary glands) were measured with a cloth measuring tape (Cloth Tape Measure, Innovation Frontier Inc., Lakewood, CA). In the second parity, piglet and sow BW, and backfat thickness was measured at farrowing and weaning according to the same procedure mentioned previously. During the lactations of both parities, total number of piglets born, numbers of piglets born alive, stillborn, and mummified were recorded, and feed intake was recorded daily. During both parities, body composition including body lipid and protein of sows at farrowing and weaning was estimated according to the equations obtained from Dourmad et al. (2008) and NRC (2012). The estimated body composition equations are: body protein = −2.28 + 0.178 × 0.96 × body weight – 0.333 × P2 backfat; body lipid = −26.4 + 0.221 × 0.96 × body weight + 1.331 × P2 backfat. Milk Sampling and Analysis Colostrum samples (30 mL) were collected within 24 h after parturition in both lactations. During the second lactation, milk samples (30 mL) were collected at 4 d before weaning. Colostrum and milk were collected from all functional mammary glands after the injection of 1 mL oxytocin (Oxytocin 20 IU/mL, Bimeda Inc., Oakbrook Terrace, IL) into the ear vein. Colostrum and milk samples were stored at −80 °C for the later analysis of composition including fat, lactose, protein, and solids-not-fat, which were determined by Milkoscan 4000 (Foss Electric, Hillerød, Denmark) and in Virginia Tech United Federation of Dairy Herd Information Association Laboratory (Blacksburg, VA) according to Garst et al. (1999). The instrument for milk composition analysis was regularly calibrated to ensure the concentrations of components of milk within a CV of 3.5% and a standard deviation smaller than 0.04. Statistical Analysis Data were analyzed as a completely randomized design. The individual sow was considered as an experimental unit. Statistical analysis was performed with the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC). To achieve the homogeneity of variances, the DDFM=SATTERTHWAITE option was used in the MODEL statement to adjust the degrees of freedom. The GROUP=EFFECT option was specified in the REPEATED statement to adjust for unequal variances. Pooled standard error was used in the data set. Data of backfat thickness or estimated body lipid were analyzed with the backfat thickness or estimated body lipid at farrowing as a covariate in both lactations (Verbeke and Molenberghs, 1997; Littell et al., 2000). Data of piglet weight at weaning, weight gain at weaning, and ADG were analyzed with piglet birth weight as a covariate in the second parity. A logistic regression (LOGISTIC procedure of SAS) was used to evaluate the effects of litter size and lactation length on culling rate and sow removal rate with chi-square tests (Peltoniemi et al., 1999; Bates et al., 2003). Mean and SEM of culling rate and sow removal rate were provided by using LSMEANS procedure with ILINK option of SAS. Both least-square means and P-value in multiple comparisons were adjusted by specifying the ADJUST=TUKEY option in the LSMEANS statement. Probability values less than 0.05 were considered statistically significant and between 0.05 and 0.10 as trends. Results Performance of Litters in the First Parity Lactation length of the first parity for LL21 and LL27 was 21.0 ± 1.4 and 27.0 ± 0.7 (P < 0.05), respectively (Table 1). After cross-fostering, the litter size of LS10 and LS13 at the beginning of the first lactation was 9.9 ± 0.5 and 13.4 ± 1.0 (P < 0.05), respectively. The number of piglets total born or born alive in LS10-LL21 was smaller (P < 0.05) than that either in LS13-LL21 or LS13-LL27. Table 1. Performance of litters in the first parity LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows 40 21 30 24 Lactation length, days2 21.3b 26.6a 20.7b 26.7a 0.2 0.217 <0.001 0.143 Litter size at birth, piglet2 9.8b 10.0b 13.3a 13.5a 0.2 <0.001 0.153 0.825 Litter size at weaning, piglet2 9.4b 8.9b 11.8a 12.5a 0.3 <0.001 0.789 0.007 Total born, piglet2 11.8b 14.0ab 14.7a 14.8a 0.5 0.002 0.048 0.059 Born alive, piglet2 11.0b 13.1ab 14.0a 14.1a 0.5 0.001 0.056 0.076 Stillborn, piglet 0.9 1.0 0.7 0.7 0.2 0.278 0.863 0.735 Mummified, piglet 0.7 0.4 0.2 0.2 0.2 0.063 0.515 0.374 Piglet weight3 At birth, kg 1.57 1.53 1.50 1.52 0.03 0.274 0.814 0.464 At day 10, kg2 3.50a 3.31ab 3.16b 3.22ab 0.09 0.033 0.528 0.192 At weaning, kg2 5.98c 7.86a 5.59c 6.71b 0.12 <0.001 <0.001 0.005 Weight gain until day 10, kg 1.93 1.77 1.66 1.70 0.08 0.051 0.540 0.247 Weight gain at weaning, kg2 4.41c 6.33a 4.09cd 5.19b 0.14 <0.001 <0.001 0.001 ADG from birth to day 10, kg2 0.192a 0.185ab 0.177ab 0.166b 0.007 0.026 0.253 0.790 ADG from birth to weaning, kg2 0.208b 0.238a 0.198b 0.195b 0.005 <0.001 0.008 0.001 Litter weight At birth, kg2 15.3b 15.2b 19.9a 20.6a 0.5 <0.001 0.580 0.448 At day 10, kg2 33.5b 31.0b 39.4a 41.6a 1.1 <0.001 0.906 0.030 At weaning, kg2 56.4c 69.6b 65.9b 83.3a 2.1 <0.001 <0.001 0.269 Weight gain at day 10, kg2 18.1ab 15.8b 19.5a 21.1a 1.0 0.001 0.680 0.043 Weight gain at weaning, kg2 41.0d 54.4b 46.0c 62.7a 1.7 <0.001 <0.001 0.336 LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows 40 21 30 24 Lactation length, days2 21.3b 26.6a 20.7b 26.7a 0.2 0.217 <0.001 0.143 Litter size at birth, piglet2 9.8b 10.0b 13.3a 13.5a 0.2 <0.001 0.153 0.825 Litter size at weaning, piglet2 9.4b 8.9b 11.8a 12.5a 0.3 <0.001 0.789 0.007 Total born, piglet2 11.8b 14.0ab 14.7a 14.8a 0.5 0.002 0.048 0.059 Born alive, piglet2 11.0b 13.1ab 14.0a 14.1a 0.5 0.001 0.056 0.076 Stillborn, piglet 0.9 1.0 0.7 0.7 0.2 0.278 0.863 0.735 Mummified, piglet 0.7 0.4 0.2 0.2 0.2 0.063 0.515 0.374 Piglet weight3 At birth, kg 1.57 1.53 1.50 1.52 0.03 0.274 0.814 0.464 At day 10, kg2 3.50a 3.31ab 3.16b 3.22ab 0.09 0.033 0.528 0.192 At weaning, kg2 5.98c 7.86a 5.59c 6.71b 0.12 <0.001 <0.001 0.005 Weight gain until day 10, kg 1.93 1.77 1.66 1.70 0.08 0.051 0.540 0.247 Weight gain at weaning, kg2 4.41c 6.33a 4.09cd 5.19b 0.14 <0.001 <0.001 0.001 ADG from birth to day 10, kg2 0.192a 0.185ab 0.177ab 0.166b 0.007 0.026 0.253 0.790 ADG from birth to weaning, kg2 0.208b 0.238a 0.198b 0.195b 0.005 <0.001 0.008 0.001 Litter weight At birth, kg2 15.3b 15.2b 19.9a 20.6a 0.5 <0.001 0.580 0.448 At day 10, kg2 33.5b 31.0b 39.4a 41.6a 1.1 <0.001 0.906 0.030 At weaning, kg2 56.4c 69.6b 65.9b 83.3a 2.1 <0.001 <0.001 0.269 Weight gain at day 10, kg2 18.1ab 15.8b 19.5a 21.1a 1.0 0.001 0.680 0.043 Weight gain at weaning, kg2 41.0d 54.4b 46.0c 62.7a 1.7 <0.001 <0.001 0.336 1LS, litter size; LL, lactation length. 2Within a row, means lacking a common superscript differ (P < 0.05). 3Average weight of piglet per litter. Open in new tab Table 1. Performance of litters in the first parity LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows 40 21 30 24 Lactation length, days2 21.3b 26.6a 20.7b 26.7a 0.2 0.217 <0.001 0.143 Litter size at birth, piglet2 9.8b 10.0b 13.3a 13.5a 0.2 <0.001 0.153 0.825 Litter size at weaning, piglet2 9.4b 8.9b 11.8a 12.5a 0.3 <0.001 0.789 0.007 Total born, piglet2 11.8b 14.0ab 14.7a 14.8a 0.5 0.002 0.048 0.059 Born alive, piglet2 11.0b 13.1ab 14.0a 14.1a 0.5 0.001 0.056 0.076 Stillborn, piglet 0.9 1.0 0.7 0.7 0.2 0.278 0.863 0.735 Mummified, piglet 0.7 0.4 0.2 0.2 0.2 0.063 0.515 0.374 Piglet weight3 At birth, kg 1.57 1.53 1.50 1.52 0.03 0.274 0.814 0.464 At day 10, kg2 3.50a 3.31ab 3.16b 3.22ab 0.09 0.033 0.528 0.192 At weaning, kg2 5.98c 7.86a 5.59c 6.71b 0.12 <0.001 <0.001 0.005 Weight gain until day 10, kg 1.93 1.77 1.66 1.70 0.08 0.051 0.540 0.247 Weight gain at weaning, kg2 4.41c 6.33a 4.09cd 5.19b 0.14 <0.001 <0.001 0.001 ADG from birth to day 10, kg2 0.192a 0.185ab 0.177ab 0.166b 0.007 0.026 0.253 0.790 ADG from birth to weaning, kg2 0.208b 0.238a 0.198b 0.195b 0.005 <0.001 0.008 0.001 Litter weight At birth, kg2 15.3b 15.2b 19.9a 20.6a 0.5 <0.001 0.580 0.448 At day 10, kg2 33.5b 31.0b 39.4a 41.6a 1.1 <0.001 0.906 0.030 At weaning, kg2 56.4c 69.6b 65.9b 83.3a 2.1 <0.001 <0.001 0.269 Weight gain at day 10, kg2 18.1ab 15.8b 19.5a 21.1a 1.0 0.001 0.680 0.043 Weight gain at weaning, kg2 41.0d 54.4b 46.0c 62.7a 1.7 <0.001 <0.001 0.336 LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows 40 21 30 24 Lactation length, days2 21.3b 26.6a 20.7b 26.7a 0.2 0.217 <0.001 0.143 Litter size at birth, piglet2 9.8b 10.0b 13.3a 13.5a 0.2 <0.001 0.153 0.825 Litter size at weaning, piglet2 9.4b 8.9b 11.8a 12.5a 0.3 <0.001 0.789 0.007 Total born, piglet2 11.8b 14.0ab 14.7a 14.8a 0.5 0.002 0.048 0.059 Born alive, piglet2 11.0b 13.1ab 14.0a 14.1a 0.5 0.001 0.056 0.076 Stillborn, piglet 0.9 1.0 0.7 0.7 0.2 0.278 0.863 0.735 Mummified, piglet 0.7 0.4 0.2 0.2 0.2 0.063 0.515 0.374 Piglet weight3 At birth, kg 1.57 1.53 1.50 1.52 0.03 0.274 0.814 0.464 At day 10, kg2 3.50a 3.31ab 3.16b 3.22ab 0.09 0.033 0.528 0.192 At weaning, kg2 5.98c 7.86a 5.59c 6.71b 0.12 <0.001 <0.001 0.005 Weight gain until day 10, kg 1.93 1.77 1.66 1.70 0.08 0.051 0.540 0.247 Weight gain at weaning, kg2 4.41c 6.33a 4.09cd 5.19b 0.14 <0.001 <0.001 0.001 ADG from birth to day 10, kg2 0.192a 0.185ab 0.177ab 0.166b 0.007 0.026 0.253 0.790 ADG from birth to weaning, kg2 0.208b 0.238a 0.198b 0.195b 0.005 <0.001 0.008 0.001 Litter weight At birth, kg2 15.3b 15.2b 19.9a 20.6a 0.5 <0.001 0.580 0.448 At day 10, kg2 33.5b 31.0b 39.4a 41.6a 1.1 <0.001 0.906 0.030 At weaning, kg2 56.4c 69.6b 65.9b 83.3a 2.1 <0.001 <0.001 0.269 Weight gain at day 10, kg2 18.1ab 15.8b 19.5a 21.1a 1.0 0.001 0.680 0.043 Weight gain at weaning, kg2 41.0d 54.4b 46.0c 62.7a 1.7 <0.001 <0.001 0.336 1LS, litter size; LL, lactation length. 2Within a row, means lacking a common superscript differ (P < 0.05). 3Average weight of piglet per litter. Open in new tab Piglet birth weight was not different between either 2 litter size groups or 2 lactation groups during the first lactation. At both day 10 of lactation and at weaning, piglet average weight and ADG in LS13 were smaller (P < 0.05) than those in LS10. Specifically, average weaning weight and weight gain of piglets in LS13-LL27 were smaller (P < 0.05) than those in LS10-LL27. Average weaning weight, weight gain, and ADG from birth to weaning in LL27 were greater (P < 0.05) than those in LL21. Specifically, ADG from birth to weaning in LS10-LL27 was greater (P < 0.05) than those in LS10-LL21. Weight of the litter at birth, at day 10 of lactation, and at weaning in LS13 was greater (P < 0.05) than those in LS10. At both day 10 of lactation and at weaning, litter weight gain in LS13 was greater (P < 0.05) than that in LS10. Litter weight and weight gain at weaning in LL27 were greater (P < 0.05) than those in LL21. Performance of Sows in the First Parity Weight of sows at farrowing, day 10 of lactation and weaning were not different between either 2 litter size groups or 2 lactation groups (Table 2). The ADFI was not different between either 2 litter size groups or 2 lactation groups. The BW loss at day 10 or at weaning in LS13 was greater (P < 0.05) as compared to those in LS10. The BW loss at weaning was not different between LL27 and LL21. Backfat thickness at farrowing in LS13 was smaller (P < 0.05) than that in LS10. The backfat loss at weaning was not different between either 2 litter size groups or 2 lactation groups. Flank-to-flank loss at day 10 of lactation and at weaning in LS13 was greater (P < 0.05) than those in LS10. Heart girth loss at weaning in LL27 was greater (P < 0.05) than those in LL21. Table 2. Performance of sows in the first parity LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows 40 21 30 24 ADFI, kg/d 4.3 4.5 4.4 4.6 0.1 0.501 0.101 0.724 Body weight At farrowing, kg2 220.5 223.7 226.8 219.9 4.0 0.755 0.632 0.199 At day 10, kg 215.9 217.6 218.7 207.5 4.9 0.386 0.261 0.129 At weaning, kg 203.9 205.6 202.4 196.3 4.1 0.241 0.629 0.400 BW loss at day 10, kg 4.6 6.1 8.1 12.3 2.7 0.012 0.135 0.476 BW loss at weaning, kg 16.6b 18.2ab 24.5a 23.6ab 2.0 0.005 0.883 0.596 Backfat thickness3 At farrowing, mm4 28.8a 30.0a 26.1ab 23.8b 1.5 0.003 0.719 0.228 At day 10, mm 22.5 22.1 21.4 23.3 1.0 0.992 0.502 0.290 At weaning, mm 20.6 19.4 19.0 19.6 0.9 0.506 0.786 0.360 Backfat loss at day 10, mm5 4.7 5.2 5.9 4.0 1.0 0.992 0.502 0.290 Backfat loss, mm6 6.7 7.8 8.2 7.6 0.9 0.506 0.786 0.360 Flank-to-flank At farrowing, cm 109.7 109.1 110.1 109.7 1.1 0.562 0.601 0.909 At day 10, cm 110.0 109.5 108.9 107.8 1.0 0.149 0.417 0.716 At weaning, cm 108.0 106.5 106.6 104.5 1.3 0.122 0.103 0.796 Loss at day 10, cm5 −0.3 −0.5 1.2 2.0 0.8 0.022 0.724 0.584 Flank-to-flank loss, cm4,6 1.7b 2.6ab 3.6ab 5.2a 1.0 0.019 0.178 0.679 Heart girth At farrowing, cm 111.8 113.0 111.8 112.3 1.4 0.735 0.489 0.773 At day 10, cm 112.1 112.6 111.3 109.5 1.1 0.128 0.633 0.352 At weaning, cm 108.3 106.5 108.0 105.5 1.2 0.545 0.056 0.754 Loss at day 10, cm5 −0.2 0.4 0.5 2.7 1.2 0.225 0.239 0.510 Heart girth loss, cm6 3.5 6.5 3.8 6.8 1.3 0.841 0.021 0.996 LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows 40 21 30 24 ADFI, kg/d 4.3 4.5 4.4 4.6 0.1 0.501 0.101 0.724 Body weight At farrowing, kg2 220.5 223.7 226.8 219.9 4.0 0.755 0.632 0.199 At day 10, kg 215.9 217.6 218.7 207.5 4.9 0.386 0.261 0.129 At weaning, kg 203.9 205.6 202.4 196.3 4.1 0.241 0.629 0.400 BW loss at day 10, kg 4.6 6.1 8.1 12.3 2.7 0.012 0.135 0.476 BW loss at weaning, kg 16.6b 18.2ab 24.5a 23.6ab 2.0 0.005 0.883 0.596 Backfat thickness3 At farrowing, mm4 28.8a 30.0a 26.1ab 23.8b 1.5 0.003 0.719 0.228 At day 10, mm 22.5 22.1 21.4 23.3 1.0 0.992 0.502 0.290 At weaning, mm 20.6 19.4 19.0 19.6 0.9 0.506 0.786 0.360 Backfat loss at day 10, mm5 4.7 5.2 5.9 4.0 1.0 0.992 0.502 0.290 Backfat loss, mm6 6.7 7.8 8.2 7.6 0.9 0.506 0.786 0.360 Flank-to-flank At farrowing, cm 109.7 109.1 110.1 109.7 1.1 0.562 0.601 0.909 At day 10, cm 110.0 109.5 108.9 107.8 1.0 0.149 0.417 0.716 At weaning, cm 108.0 106.5 106.6 104.5 1.3 0.122 0.103 0.796 Loss at day 10, cm5 −0.3 −0.5 1.2 2.0 0.8 0.022 0.724 0.584 Flank-to-flank loss, cm4,6 1.7b 2.6ab 3.6ab 5.2a 1.0 0.019 0.178 0.679 Heart girth At farrowing, cm 111.8 113.0 111.8 112.3 1.4 0.735 0.489 0.773 At day 10, cm 112.1 112.6 111.3 109.5 1.1 0.128 0.633 0.352 At weaning, cm 108.3 106.5 108.0 105.5 1.2 0.545 0.056 0.754 Loss at day 10, cm5 −0.2 0.4 0.5 2.7 1.2 0.225 0.239 0.510 Heart girth loss, cm6 3.5 6.5 3.8 6.8 1.3 0.841 0.021 0.996 1LS, litter size; LL, lactation length. 2Sows were weighed within 24 h after farrowing. 3The sample size in backfat measurement was 23, 20, 16, and 11 for treatment LS10-LL21, LS10-LL27, LS13-LL21, and LS13-LL27, respectively. Data of backfat thickness at day 10 of lactation, at weaning, backfat loss at day 10 of lactation, and backfat loss at weaning were analyzed with backfat at farrowing as a covariate. 4Within a row, means lacking a common superscript differ (P < 0.05). 5Backfat loss at d 10 = backfat thickness at farrowing—backfat thickness at d 10 of lactation. Flank loss and heart girth loss calculations at d 10 of lactation and weaning were similar to backfat loss calculation. 6Backfat loss = backfat thickness at farrowing—backfat thickness at weaning; Flank-to-flank loss and heart girth loss calculations were the same as backfat loss calculation. Open in new tab Table 2. Performance of sows in the first parity LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows 40 21 30 24 ADFI, kg/d 4.3 4.5 4.4 4.6 0.1 0.501 0.101 0.724 Body weight At farrowing, kg2 220.5 223.7 226.8 219.9 4.0 0.755 0.632 0.199 At day 10, kg 215.9 217.6 218.7 207.5 4.9 0.386 0.261 0.129 At weaning, kg 203.9 205.6 202.4 196.3 4.1 0.241 0.629 0.400 BW loss at day 10, kg 4.6 6.1 8.1 12.3 2.7 0.012 0.135 0.476 BW loss at weaning, kg 16.6b 18.2ab 24.5a 23.6ab 2.0 0.005 0.883 0.596 Backfat thickness3 At farrowing, mm4 28.8a 30.0a 26.1ab 23.8b 1.5 0.003 0.719 0.228 At day 10, mm 22.5 22.1 21.4 23.3 1.0 0.992 0.502 0.290 At weaning, mm 20.6 19.4 19.0 19.6 0.9 0.506 0.786 0.360 Backfat loss at day 10, mm5 4.7 5.2 5.9 4.0 1.0 0.992 0.502 0.290 Backfat loss, mm6 6.7 7.8 8.2 7.6 0.9 0.506 0.786 0.360 Flank-to-flank At farrowing, cm 109.7 109.1 110.1 109.7 1.1 0.562 0.601 0.909 At day 10, cm 110.0 109.5 108.9 107.8 1.0 0.149 0.417 0.716 At weaning, cm 108.0 106.5 106.6 104.5 1.3 0.122 0.103 0.796 Loss at day 10, cm5 −0.3 −0.5 1.2 2.0 0.8 0.022 0.724 0.584 Flank-to-flank loss, cm4,6 1.7b 2.6ab 3.6ab 5.2a 1.0 0.019 0.178 0.679 Heart girth At farrowing, cm 111.8 113.0 111.8 112.3 1.4 0.735 0.489 0.773 At day 10, cm 112.1 112.6 111.3 109.5 1.1 0.128 0.633 0.352 At weaning, cm 108.3 106.5 108.0 105.5 1.2 0.545 0.056 0.754 Loss at day 10, cm5 −0.2 0.4 0.5 2.7 1.2 0.225 0.239 0.510 Heart girth loss, cm6 3.5 6.5 3.8 6.8 1.3 0.841 0.021 0.996 LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows 40 21 30 24 ADFI, kg/d 4.3 4.5 4.4 4.6 0.1 0.501 0.101 0.724 Body weight At farrowing, kg2 220.5 223.7 226.8 219.9 4.0 0.755 0.632 0.199 At day 10, kg 215.9 217.6 218.7 207.5 4.9 0.386 0.261 0.129 At weaning, kg 203.9 205.6 202.4 196.3 4.1 0.241 0.629 0.400 BW loss at day 10, kg 4.6 6.1 8.1 12.3 2.7 0.012 0.135 0.476 BW loss at weaning, kg 16.6b 18.2ab 24.5a 23.6ab 2.0 0.005 0.883 0.596 Backfat thickness3 At farrowing, mm4 28.8a 30.0a 26.1ab 23.8b 1.5 0.003 0.719 0.228 At day 10, mm 22.5 22.1 21.4 23.3 1.0 0.992 0.502 0.290 At weaning, mm 20.6 19.4 19.0 19.6 0.9 0.506 0.786 0.360 Backfat loss at day 10, mm5 4.7 5.2 5.9 4.0 1.0 0.992 0.502 0.290 Backfat loss, mm6 6.7 7.8 8.2 7.6 0.9 0.506 0.786 0.360 Flank-to-flank At farrowing, cm 109.7 109.1 110.1 109.7 1.1 0.562 0.601 0.909 At day 10, cm 110.0 109.5 108.9 107.8 1.0 0.149 0.417 0.716 At weaning, cm 108.0 106.5 106.6 104.5 1.3 0.122 0.103 0.796 Loss at day 10, cm5 −0.3 −0.5 1.2 2.0 0.8 0.022 0.724 0.584 Flank-to-flank loss, cm4,6 1.7b 2.6ab 3.6ab 5.2a 1.0 0.019 0.178 0.679 Heart girth At farrowing, cm 111.8 113.0 111.8 112.3 1.4 0.735 0.489 0.773 At day 10, cm 112.1 112.6 111.3 109.5 1.1 0.128 0.633 0.352 At weaning, cm 108.3 106.5 108.0 105.5 1.2 0.545 0.056 0.754 Loss at day 10, cm5 −0.2 0.4 0.5 2.7 1.2 0.225 0.239 0.510 Heart girth loss, cm6 3.5 6.5 3.8 6.8 1.3 0.841 0.021 0.996 1LS, litter size; LL, lactation length. 2Sows were weighed within 24 h after farrowing. 3The sample size in backfat measurement was 23, 20, 16, and 11 for treatment LS10-LL21, LS10-LL27, LS13-LL21, and LS13-LL27, respectively. Data of backfat thickness at day 10 of lactation, at weaning, backfat loss at day 10 of lactation, and backfat loss at weaning were analyzed with backfat at farrowing as a covariate. 4Within a row, means lacking a common superscript differ (P < 0.05). 5Backfat loss at d 10 = backfat thickness at farrowing—backfat thickness at d 10 of lactation. Flank loss and heart girth loss calculations at d 10 of lactation and weaning were similar to backfat loss calculation. 6Backfat loss = backfat thickness at farrowing—backfat thickness at weaning; Flank-to-flank loss and heart girth loss calculations were the same as backfat loss calculation. Open in new tab Culling Rate and Sow Removal Rate In the second parity, the culling rate was not affected by litter size, lactation length, and their interaction (Table 3). Sows in LS13 tended to have a greater (P = 0.075) removal rate than sows in LS10. Sows in LL27 had a smaller (P < 0.05) removal rate in the second parity than sows in LL21. Table 3. Logistic regression of litter size and lactation length on culling rate and sow removal rate in the second parity LS10 LS13 P-value > Chi-square1 Item LL21 LL27 LL21 L L27 SEM LS LL LS × LL Culling rate, %2 27.5 14.3 30.0 25.0 7.6 0.257 0.389 0.546 Sow removal rate, %3 50.0 14.3 53.3 41.7 7.9 0.075 0.011 0.138 LS10 LS13 P-value > Chi-square1 Item LL21 LL27 LL21 L L27 SEM LS LL LS × LL Culling rate, %2 27.5 14.3 30.0 25.0 7.6 0.257 0.389 0.546 Sow removal rate, %3 50.0 14.3 53.3 41.7 7.9 0.075 0.011 0.138 1LS, litter size; LL, lactation length. Difference was received from the F-test, the null hypothesis was tested in a Chi-square distribution. 2Data of culling rate were cataloged as either cull or not cull for each sow. Data of culling rate were analyzed by using the LOGISTIC procedure (SAS Inst. Inc., Cary, NC). Probability modeled was cull = “YES”. Culling reason includes death, lameness, low productivity, and so on. 3Reason to remove sows from experiment including culling, failure to conceive, anestrus, abortion because rebreeding after the pregnancy test would lead to additional days to recover and grow after the first parity, which would affect the treatment effects (suckling intensity). Open in new tab Table 3. Logistic regression of litter size and lactation length on culling rate and sow removal rate in the second parity LS10 LS13 P-value > Chi-square1 Item LL21 LL27 LL21 L L27 SEM LS LL LS × LL Culling rate, %2 27.5 14.3 30.0 25.0 7.6 0.257 0.389 0.546 Sow removal rate, %3 50.0 14.3 53.3 41.7 7.9 0.075 0.011 0.138 LS10 LS13 P-value > Chi-square1 Item LL21 LL27 LL21 L L27 SEM LS LL LS × LL Culling rate, %2 27.5 14.3 30.0 25.0 7.6 0.257 0.389 0.546 Sow removal rate, %3 50.0 14.3 53.3 41.7 7.9 0.075 0.011 0.138 1LS, litter size; LL, lactation length. Difference was received from the F-test, the null hypothesis was tested in a Chi-square distribution. 2Data of culling rate were cataloged as either cull or not cull for each sow. Data of culling rate were analyzed by using the LOGISTIC procedure (SAS Inst. Inc., Cary, NC). Probability modeled was cull = “YES”. Culling reason includes death, lameness, low productivity, and so on. 3Reason to remove sows from experiment including culling, failure to conceive, anestrus, abortion because rebreeding after the pregnancy test would lead to additional days to recover and grow after the first parity, which would affect the treatment effects (suckling intensity). Open in new tab Performance of Litters and Sows in the Second Parity and within 2 Cycles In the second parity, lactation length and litter size at birth was not different between either 2 litter size groups or 2 lactation groups (Table 4). The number of piglets total born, born alive, stillborn, and mummified, and birth weight during the second lactation was not affected by the 2 factors and their interaction. Either piglet or litter weaning weight and weight gain were not affected by previous litter size, lactation length, and their interaction. Table 4. Performance of sows and litters in the second parity LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS x LL Number of sows2 20 18 14 14 Lactation length, days 20.6 20.8 20.6 20.6 0.2 0.330 0.433 0.433 Litter size at birth, piglet 13.6 12.1 13.8 13.1 1.0 0.510 0.209 0.656 Litter size after CF, piglet3 10.1 10.1 10.1 10.3 0.3 0.527 0.771 0.788 Litter size at weaning, piglet 10.1 10.1 10.2 10.3 0.2 0.434 0.878 0.896 Total born, piglet 13.2 13.6 13.5 13.4 0.7 0.896 0.844 0.780 Born alive, piglet 12.5 12.9 13.0 13.0 0.8 0.679 0.784 0.784 Stillborn, piglet 0.7 0.7 0.5 0.4 0.2 0.289 0.799 0.926 Mummified, piglet 0.2 0.0 0.1 0.0 0.1 0.455 0.118 0.455 Piglet weight4,5 Weight at birth, kg 1.49 1.58 1.53 1.58 0.07 0.813 0.237 0.738 Weight after CF, kg 1.55 1.63 1.53 1.64 0.06 0.851 0.075 0.753 Weight at weaning, kg 6.80 7.18 6.95 6.81 0.16 0.489 0.506 0.112 ADG, kg 0.253 0.269 0.261 0.254 0.008 0.675 0.585 0.158 Litter weight Weight at birth, kg 20.1 18.9 20.4 20.0 1.2 0.484 0.474 0.702 Weight after CF, kg 15.6 16.4 15.6 16.8 0.7 0.771 0.129 0.766 Weight at weaning, kg 67.4 72.9 69.5 70.9 2.2 0.977 0.121 0.354 Weight gain, kg 51.8 56.5 53.9 54.2 1.8 0.945 0.174 0.214 Sow lactation ADFI, kg/d6 7.1 7.4 7.1 7.1 0.2 0.428 0.546 0.588 Sow weight Gestation weight gain, kg7,8 33.2B 56.1A 50.2AB 41.8AB 7.1 0.843 0.278 0.023 At farrowing, kg 235.5 250.4 251.0 235.5 6.9 0.969 0.962 0.027 At weaning, kg 228.2 243.1 240.2 234.8 7.3 0.774 0.459 0.115 BW loss, kg7,9 7.3a 7.3a 10.8a 0.7b 2.5 0.490 0.029 0.029 Backfat thickness10 At farrowing, mm 19.8 20.6 18.2 17.3 1.1 0.023 0.956 0.411 At weaning, mm 16.3 17.2 18.1 18.6 0.7 0.010 0.236 0.742 Backfat loss, mm 2.8 2.0 1.1 0.6 0.5 0.010 0.236 0.742 Within 2 cycles, from the farrowing of parity 1 to the weaning of parity 2 Body weight gain, kg 0.2 25.3 12.8 13.8 8.5 0.945 0.095 0.120 Backfat loss, mm10 13.2 12.0 8.4 5.5 3.2 0.050 0.453 0.777 LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS x LL Number of sows2 20 18 14 14 Lactation length, days 20.6 20.8 20.6 20.6 0.2 0.330 0.433 0.433 Litter size at birth, piglet 13.6 12.1 13.8 13.1 1.0 0.510 0.209 0.656 Litter size after CF, piglet3 10.1 10.1 10.1 10.3 0.3 0.527 0.771 0.788 Litter size at weaning, piglet 10.1 10.1 10.2 10.3 0.2 0.434 0.878 0.896 Total born, piglet 13.2 13.6 13.5 13.4 0.7 0.896 0.844 0.780 Born alive, piglet 12.5 12.9 13.0 13.0 0.8 0.679 0.784 0.784 Stillborn, piglet 0.7 0.7 0.5 0.4 0.2 0.289 0.799 0.926 Mummified, piglet 0.2 0.0 0.1 0.0 0.1 0.455 0.118 0.455 Piglet weight4,5 Weight at birth, kg 1.49 1.58 1.53 1.58 0.07 0.813 0.237 0.738 Weight after CF, kg 1.55 1.63 1.53 1.64 0.06 0.851 0.075 0.753 Weight at weaning, kg 6.80 7.18 6.95 6.81 0.16 0.489 0.506 0.112 ADG, kg 0.253 0.269 0.261 0.254 0.008 0.675 0.585 0.158 Litter weight Weight at birth, kg 20.1 18.9 20.4 20.0 1.2 0.484 0.474 0.702 Weight after CF, kg 15.6 16.4 15.6 16.8 0.7 0.771 0.129 0.766 Weight at weaning, kg 67.4 72.9 69.5 70.9 2.2 0.977 0.121 0.354 Weight gain, kg 51.8 56.5 53.9 54.2 1.8 0.945 0.174 0.214 Sow lactation ADFI, kg/d6 7.1 7.4 7.1 7.1 0.2 0.428 0.546 0.588 Sow weight Gestation weight gain, kg7,8 33.2B 56.1A 50.2AB 41.8AB 7.1 0.843 0.278 0.023 At farrowing, kg 235.5 250.4 251.0 235.5 6.9 0.969 0.962 0.027 At weaning, kg 228.2 243.1 240.2 234.8 7.3 0.774 0.459 0.115 BW loss, kg7,9 7.3a 7.3a 10.8a 0.7b 2.5 0.490 0.029 0.029 Backfat thickness10 At farrowing, mm 19.8 20.6 18.2 17.3 1.1 0.023 0.956 0.411 At weaning, mm 16.3 17.2 18.1 18.6 0.7 0.010 0.236 0.742 Backfat loss, mm 2.8 2.0 1.1 0.6 0.5 0.010 0.236 0.742 Within 2 cycles, from the farrowing of parity 1 to the weaning of parity 2 Body weight gain, kg 0.2 25.3 12.8 13.8 8.5 0.945 0.095 0.120 Backfat loss, mm10 13.2 12.0 8.4 5.5 3.2 0.050 0.453 0.777 1LS, litter size; LL, lactation length. 2Number of corresponding sows were used in the analysis. Some sows were removed from the experiment due to abortion, pregnancy failure, lameness, vulva discharge, not conceive, and death. 3CF is cross-fostering. 4Average weight of piglet per litter 5Data of piglet weight at weaning, weight gain at weaning, and ADG were analyzed with the average piglet weight after cross-fostering as a covariate. 6Sample size in ADFI of sow was 20, 16, 12, and 13 for LS10-LL21, LS10-LL27, LS13-LL21, and LS13-LL27, respectively. 7Within a row, means lacking a common uppercase superscript tend to differ (0.05 ≤ P < 0.10); means lacking a common lowercase superscript differ (P < 0.05). 8Gestation weight gain = weight at farrowing in the second lactation – weight at weaning in the first lactation. 9Sample size for sow weight loss was 18, 16, 11, and 13 sows for LS10-LL21, LS10-LL27, LS13-LL21, and LS13-LL27, respectively; BW loss = weight at farrowing—weight at weaning. 10Backfat thickness at weaning and backfat loss was analyzed with backfat thickness at farrowing as a covariate. Backfat loss = backfat thickness at farrowing—backfat thickness at weaning. Open in new tab Table 4. Performance of sows and litters in the second parity LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS x LL Number of sows2 20 18 14 14 Lactation length, days 20.6 20.8 20.6 20.6 0.2 0.330 0.433 0.433 Litter size at birth, piglet 13.6 12.1 13.8 13.1 1.0 0.510 0.209 0.656 Litter size after CF, piglet3 10.1 10.1 10.1 10.3 0.3 0.527 0.771 0.788 Litter size at weaning, piglet 10.1 10.1 10.2 10.3 0.2 0.434 0.878 0.896 Total born, piglet 13.2 13.6 13.5 13.4 0.7 0.896 0.844 0.780 Born alive, piglet 12.5 12.9 13.0 13.0 0.8 0.679 0.784 0.784 Stillborn, piglet 0.7 0.7 0.5 0.4 0.2 0.289 0.799 0.926 Mummified, piglet 0.2 0.0 0.1 0.0 0.1 0.455 0.118 0.455 Piglet weight4,5 Weight at birth, kg 1.49 1.58 1.53 1.58 0.07 0.813 0.237 0.738 Weight after CF, kg 1.55 1.63 1.53 1.64 0.06 0.851 0.075 0.753 Weight at weaning, kg 6.80 7.18 6.95 6.81 0.16 0.489 0.506 0.112 ADG, kg 0.253 0.269 0.261 0.254 0.008 0.675 0.585 0.158 Litter weight Weight at birth, kg 20.1 18.9 20.4 20.0 1.2 0.484 0.474 0.702 Weight after CF, kg 15.6 16.4 15.6 16.8 0.7 0.771 0.129 0.766 Weight at weaning, kg 67.4 72.9 69.5 70.9 2.2 0.977 0.121 0.354 Weight gain, kg 51.8 56.5 53.9 54.2 1.8 0.945 0.174 0.214 Sow lactation ADFI, kg/d6 7.1 7.4 7.1 7.1 0.2 0.428 0.546 0.588 Sow weight Gestation weight gain, kg7,8 33.2B 56.1A 50.2AB 41.8AB 7.1 0.843 0.278 0.023 At farrowing, kg 235.5 250.4 251.0 235.5 6.9 0.969 0.962 0.027 At weaning, kg 228.2 243.1 240.2 234.8 7.3 0.774 0.459 0.115 BW loss, kg7,9 7.3a 7.3a 10.8a 0.7b 2.5 0.490 0.029 0.029 Backfat thickness10 At farrowing, mm 19.8 20.6 18.2 17.3 1.1 0.023 0.956 0.411 At weaning, mm 16.3 17.2 18.1 18.6 0.7 0.010 0.236 0.742 Backfat loss, mm 2.8 2.0 1.1 0.6 0.5 0.010 0.236 0.742 Within 2 cycles, from the farrowing of parity 1 to the weaning of parity 2 Body weight gain, kg 0.2 25.3 12.8 13.8 8.5 0.945 0.095 0.120 Backfat loss, mm10 13.2 12.0 8.4 5.5 3.2 0.050 0.453 0.777 LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS x LL Number of sows2 20 18 14 14 Lactation length, days 20.6 20.8 20.6 20.6 0.2 0.330 0.433 0.433 Litter size at birth, piglet 13.6 12.1 13.8 13.1 1.0 0.510 0.209 0.656 Litter size after CF, piglet3 10.1 10.1 10.1 10.3 0.3 0.527 0.771 0.788 Litter size at weaning, piglet 10.1 10.1 10.2 10.3 0.2 0.434 0.878 0.896 Total born, piglet 13.2 13.6 13.5 13.4 0.7 0.896 0.844 0.780 Born alive, piglet 12.5 12.9 13.0 13.0 0.8 0.679 0.784 0.784 Stillborn, piglet 0.7 0.7 0.5 0.4 0.2 0.289 0.799 0.926 Mummified, piglet 0.2 0.0 0.1 0.0 0.1 0.455 0.118 0.455 Piglet weight4,5 Weight at birth, kg 1.49 1.58 1.53 1.58 0.07 0.813 0.237 0.738 Weight after CF, kg 1.55 1.63 1.53 1.64 0.06 0.851 0.075 0.753 Weight at weaning, kg 6.80 7.18 6.95 6.81 0.16 0.489 0.506 0.112 ADG, kg 0.253 0.269 0.261 0.254 0.008 0.675 0.585 0.158 Litter weight Weight at birth, kg 20.1 18.9 20.4 20.0 1.2 0.484 0.474 0.702 Weight after CF, kg 15.6 16.4 15.6 16.8 0.7 0.771 0.129 0.766 Weight at weaning, kg 67.4 72.9 69.5 70.9 2.2 0.977 0.121 0.354 Weight gain, kg 51.8 56.5 53.9 54.2 1.8 0.945 0.174 0.214 Sow lactation ADFI, kg/d6 7.1 7.4 7.1 7.1 0.2 0.428 0.546 0.588 Sow weight Gestation weight gain, kg7,8 33.2B 56.1A 50.2AB 41.8AB 7.1 0.843 0.278 0.023 At farrowing, kg 235.5 250.4 251.0 235.5 6.9 0.969 0.962 0.027 At weaning, kg 228.2 243.1 240.2 234.8 7.3 0.774 0.459 0.115 BW loss, kg7,9 7.3a 7.3a 10.8a 0.7b 2.5 0.490 0.029 0.029 Backfat thickness10 At farrowing, mm 19.8 20.6 18.2 17.3 1.1 0.023 0.956 0.411 At weaning, mm 16.3 17.2 18.1 18.6 0.7 0.010 0.236 0.742 Backfat loss, mm 2.8 2.0 1.1 0.6 0.5 0.010 0.236 0.742 Within 2 cycles, from the farrowing of parity 1 to the weaning of parity 2 Body weight gain, kg 0.2 25.3 12.8 13.8 8.5 0.945 0.095 0.120 Backfat loss, mm10 13.2 12.0 8.4 5.5 3.2 0.050 0.453 0.777 1LS, litter size; LL, lactation length. 2Number of corresponding sows were used in the analysis. Some sows were removed from the experiment due to abortion, pregnancy failure, lameness, vulva discharge, not conceive, and death. 3CF is cross-fostering. 4Average weight of piglet per litter 5Data of piglet weight at weaning, weight gain at weaning, and ADG were analyzed with the average piglet weight after cross-fostering as a covariate. 6Sample size in ADFI of sow was 20, 16, 12, and 13 for LS10-LL21, LS10-LL27, LS13-LL21, and LS13-LL27, respectively. 7Within a row, means lacking a common uppercase superscript tend to differ (0.05 ≤ P < 0.10); means lacking a common lowercase superscript differ (P < 0.05). 8Gestation weight gain = weight at farrowing in the second lactation – weight at weaning in the first lactation. 9Sample size for sow weight loss was 18, 16, 11, and 13 sows for LS10-LL21, LS10-LL27, LS13-LL21, and LS13-LL27, respectively; BW loss = weight at farrowing—weight at weaning. 10Backfat thickness at weaning and backfat loss was analyzed with backfat thickness at farrowing as a covariate. Backfat loss = backfat thickness at farrowing—backfat thickness at weaning. Open in new tab In the second parity, sows in LS10-LL27 tended to have a greater weight gain (P = 0.098) during the following gestation than sows in LS10-LL21. The lactational ADFI was not affected by previous litter size, lactation length, and their interaction. The BW of sows at farrowing and weaning was not affected by 2 factors and their interaction. Sows in LL27 had a smaller BW loss (P < 0.05) during the second lactation than sows in LL21, whereas BW loss was not different between LS13 and LS10. Backfat thickness at farrowing in LS13 was smaller (P < 0.05) than that in LS10. Backfat loss in LS13 was smaller (P < 0.05) than that in LS10 and backfat thickness at weaning in LS13 was greater (P < 0.05) than that in LS10 with the backfat thickness at farrowing as a covariate. Backfat thickness at farrowing and weaning and backfat loss did not differ between LL27 and LL21. Within 2 cycles (from the farrowing of the first parity to the weaning of the second parity), body weight gain was not different between LS13 and LS10. Sows in LL27 tended to have a greater (P = 0.095) body weight gain than sows in LL21. Sows in LS13 tended to have a smaller backfat loss (P = 0.050) than sows in LS10. Backfat loss within 2 cycles was not different between LL27 and LL21. Estimated Body Composition of Sows in the First and Second Parities In the first parity, estimated body protein at farrowing was not different between either 2 litter size groups or 2 lactation length groups (Table 5). The estimated body lipid at farrowing in LS13 was smaller (P < 0.05) than that in LS10. Estimated body lipid at weaning and body lipid loss was not different between LS13 and LS10 when the farrowing estimated body lipid was used as a covariance. The predicted body protein loss in LS13 was greater (P < 0.05) than that in LS10. The predicted body protein and lipid loss did not differ between LL27 and LL21. Table 5. Estimated body composition of sows in the first and second parities1 LS10 LS13 P-value2 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows in parity 1 21 7 16 11 Estimated body composition at farrowing in parity 1 Body protein, kg 30.8 31.6 31.4 32.7 1.3 0.463 0.374 0.838 Body lipid, kg 59.1 61.8 55.2 53.0 2.2 0.022 0.924 0.340 Estimated body composition at weaning in parity 1 Body protein, kg 30.6 32.9 30.2 31.2 1.1 0.447 0.215 0.620 Body lipid, kg 44.2 44.5 42.0 42.4 1.9 0.912 0.866 0.325 Predicted body composition change at lactation in parity 1 Body protein, kg −0.2 1.3 −1.2 −1.5 0.6 0.004 0.326 0.146 Body lipid, kg −13.6 −16.6 −14.4 −10.9 1.9 0.297 0.915 0.181 Number of sows in parity 2 18 16 11 13 Estimated body composition at farrowing in parity 2 Body protein, kg 35.8 38.0 38.9 36.7 1.0 0.381 0.967 0.031 Body lipid, kg3 50.3AB 55.0A 51.9AB 46.9B 3.0 0.205 0.960 0.060 Estimated body composition at weaning in parity 2 Body protein, kg 35.6 37.6 37.5 36.6 1.1 0.611 0.534 0.123 Body lipid, kg 44.8 50.0 47.8 46.4 2.0 0.916 0.443 0.194 Predicted body composition change at lactation in parity 2 Body protein, kg −0.3 −0.4 −1.4 0 0.4 0.368 0.160 0.101 Body lipid, kg4 −5.5a −5.0a −4.1ab −0.5b 1.2 <0.001 <0.001 0.001 LS10 LS13 P-value2 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows in parity 1 21 7 16 11 Estimated body composition at farrowing in parity 1 Body protein, kg 30.8 31.6 31.4 32.7 1.3 0.463 0.374 0.838 Body lipid, kg 59.1 61.8 55.2 53.0 2.2 0.022 0.924 0.340 Estimated body composition at weaning in parity 1 Body protein, kg 30.6 32.9 30.2 31.2 1.1 0.447 0.215 0.620 Body lipid, kg 44.2 44.5 42.0 42.4 1.9 0.912 0.866 0.325 Predicted body composition change at lactation in parity 1 Body protein, kg −0.2 1.3 −1.2 −1.5 0.6 0.004 0.326 0.146 Body lipid, kg −13.6 −16.6 −14.4 −10.9 1.9 0.297 0.915 0.181 Number of sows in parity 2 18 16 11 13 Estimated body composition at farrowing in parity 2 Body protein, kg 35.8 38.0 38.9 36.7 1.0 0.381 0.967 0.031 Body lipid, kg3 50.3AB 55.0A 51.9AB 46.9B 3.0 0.205 0.960 0.060 Estimated body composition at weaning in parity 2 Body protein, kg 35.6 37.6 37.5 36.6 1.1 0.611 0.534 0.123 Body lipid, kg 44.8 50.0 47.8 46.4 2.0 0.916 0.443 0.194 Predicted body composition change at lactation in parity 2 Body protein, kg −0.3 −0.4 −1.4 0 0.4 0.368 0.160 0.101 Body lipid, kg4 −5.5a −5.0a −4.1ab −0.5b 1.2 <0.001 <0.001 0.001 1Estimation of body composition at farrrowing and weaning were made from the following equations (Dourmad et al., 2008; NRC, 2012): Body protein = −2.28 + 0.178 × 0.96 × body weight – 0.333 × P2 backfat. Body lipid = −26.4 + 0.221 × 0.96 × body weight + 1.331 × P2 backfat. 2LS, litter size; LL, lactation length. 3Within a row, means lacking a common uppercase superscript tend to differ (0.05 ≤ P < 0.10). 4Within a row, means lacking a common superscript differ (P < 0.05). Open in new tab Table 5. Estimated body composition of sows in the first and second parities1 LS10 LS13 P-value2 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows in parity 1 21 7 16 11 Estimated body composition at farrowing in parity 1 Body protein, kg 30.8 31.6 31.4 32.7 1.3 0.463 0.374 0.838 Body lipid, kg 59.1 61.8 55.2 53.0 2.2 0.022 0.924 0.340 Estimated body composition at weaning in parity 1 Body protein, kg 30.6 32.9 30.2 31.2 1.1 0.447 0.215 0.620 Body lipid, kg 44.2 44.5 42.0 42.4 1.9 0.912 0.866 0.325 Predicted body composition change at lactation in parity 1 Body protein, kg −0.2 1.3 −1.2 −1.5 0.6 0.004 0.326 0.146 Body lipid, kg −13.6 −16.6 −14.4 −10.9 1.9 0.297 0.915 0.181 Number of sows in parity 2 18 16 11 13 Estimated body composition at farrowing in parity 2 Body protein, kg 35.8 38.0 38.9 36.7 1.0 0.381 0.967 0.031 Body lipid, kg3 50.3AB 55.0A 51.9AB 46.9B 3.0 0.205 0.960 0.060 Estimated body composition at weaning in parity 2 Body protein, kg 35.6 37.6 37.5 36.6 1.1 0.611 0.534 0.123 Body lipid, kg 44.8 50.0 47.8 46.4 2.0 0.916 0.443 0.194 Predicted body composition change at lactation in parity 2 Body protein, kg −0.3 −0.4 −1.4 0 0.4 0.368 0.160 0.101 Body lipid, kg4 −5.5a −5.0a −4.1ab −0.5b 1.2 <0.001 <0.001 0.001 LS10 LS13 P-value2 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Number of sows in parity 1 21 7 16 11 Estimated body composition at farrowing in parity 1 Body protein, kg 30.8 31.6 31.4 32.7 1.3 0.463 0.374 0.838 Body lipid, kg 59.1 61.8 55.2 53.0 2.2 0.022 0.924 0.340 Estimated body composition at weaning in parity 1 Body protein, kg 30.6 32.9 30.2 31.2 1.1 0.447 0.215 0.620 Body lipid, kg 44.2 44.5 42.0 42.4 1.9 0.912 0.866 0.325 Predicted body composition change at lactation in parity 1 Body protein, kg −0.2 1.3 −1.2 −1.5 0.6 0.004 0.326 0.146 Body lipid, kg −13.6 −16.6 −14.4 −10.9 1.9 0.297 0.915 0.181 Number of sows in parity 2 18 16 11 13 Estimated body composition at farrowing in parity 2 Body protein, kg 35.8 38.0 38.9 36.7 1.0 0.381 0.967 0.031 Body lipid, kg3 50.3AB 55.0A 51.9AB 46.9B 3.0 0.205 0.960 0.060 Estimated body composition at weaning in parity 2 Body protein, kg 35.6 37.6 37.5 36.6 1.1 0.611 0.534 0.123 Body lipid, kg 44.8 50.0 47.8 46.4 2.0 0.916 0.443 0.194 Predicted body composition change at lactation in parity 2 Body protein, kg −0.3 −0.4 −1.4 0 0.4 0.368 0.160 0.101 Body lipid, kg4 −5.5a −5.0a −4.1ab −0.5b 1.2 <0.001 <0.001 0.001 1Estimation of body composition at farrrowing and weaning were made from the following equations (Dourmad et al., 2008; NRC, 2012): Body protein = −2.28 + 0.178 × 0.96 × body weight – 0.333 × P2 backfat. Body lipid = −26.4 + 0.221 × 0.96 × body weight + 1.331 × P2 backfat. 2LS, litter size; LL, lactation length. 3Within a row, means lacking a common uppercase superscript tend to differ (0.05 ≤ P < 0.10). 4Within a row, means lacking a common superscript differ (P < 0.05). Open in new tab During the second lactation, the estimated body lipid at farrowing in LS13-LL27 tended to be smaller (P < 0.05) than that in LS10-LL27. Estimated body lipid and protein at weaning in LS13 were not different between either 2 litter size groups or 2 lactation length groups. The predicted body lipid loss during lactation in LS13 was smaller (P < 0.05) than that in LS10. The predicted body lipid loss during lactation in LL27 was smaller (P < 0.05) than that in LL21. Composition of Colostrum and Milk in the First and Second Parity Sows During the second lactation, concentrations of colostrum fat, lactose, protein, and solids-not-fat were not affected by 2 factors and their interaction (Table 6). The composition of milk in LS13 and LS10 did not differ. The concentration of milk fat in LL27 was smaller (P < 0.05) than that in LL21 when litter size was 10 piglets during the first lactation. Table 6. Composition of colostrum and milk in the first and second parities (wet basis) LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Numbers of sows in the first parity 10 18 15 9 Colostrum, % Fat 10.3 7.5 8.5 9.0 1.1 0.855 0.310 0.121 Protein 9.1 6.2 7.5 8.9 1.0 0.608 0.482 0.054 Solids-not-fat 14.1 13.1 12.6 13.9 1.0 0.746 0.882 0.246 Lactose2 3.2b 4.2a 3.2b 3.4ab 0.3 0.097 0.029 0.089 Numbers of sows in the second parity 20 18 14 14 Colostrum, % Fat 7.9 7.5 7.1 8.0 0.6 0.818 0.790 0.341 Protein 9.9 10.5 10.4 9.7 0.8 0.803 0.997 0.341 Solids-not-fat 14.4 14.8 14.9 14.4 0.6 0.977 0.949 0.404 Lactose 2.9 2.8 3.0 3.1 0.1 0.172 0.790 0.278 Milk, day 18 of lactation, % Fat2 8.4b 8.4b 9.7a 7.4b 0.4 0.625 0.014 0.014 Protein 4.5 4.5 4.7 4.4 0.1 0.821 0.221 0.251 Solids-non-fat 11.6 11.7 11.6 11.5 0.1 0.539 0.916 0.725 Lactose 5.2 5.3 5.0 5.2 0.1 0.317 0.286 0.495 LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Numbers of sows in the first parity 10 18 15 9 Colostrum, % Fat 10.3 7.5 8.5 9.0 1.1 0.855 0.310 0.121 Protein 9.1 6.2 7.5 8.9 1.0 0.608 0.482 0.054 Solids-not-fat 14.1 13.1 12.6 13.9 1.0 0.746 0.882 0.246 Lactose2 3.2b 4.2a 3.2b 3.4ab 0.3 0.097 0.029 0.089 Numbers of sows in the second parity 20 18 14 14 Colostrum, % Fat 7.9 7.5 7.1 8.0 0.6 0.818 0.790 0.341 Protein 9.9 10.5 10.4 9.7 0.8 0.803 0.997 0.341 Solids-not-fat 14.4 14.8 14.9 14.4 0.6 0.977 0.949 0.404 Lactose 2.9 2.8 3.0 3.1 0.1 0.172 0.790 0.278 Milk, day 18 of lactation, % Fat2 8.4b 8.4b 9.7a 7.4b 0.4 0.625 0.014 0.014 Protein 4.5 4.5 4.7 4.4 0.1 0.821 0.221 0.251 Solids-non-fat 11.6 11.7 11.6 11.5 0.1 0.539 0.916 0.725 Lactose 5.2 5.3 5.0 5.2 0.1 0.317 0.286 0.495 1LS, litter size; LL, lactation length. 2Within a row, means lacking a common superscript differ (P < 0.05). Open in new tab Table 6. Composition of colostrum and milk in the first and second parities (wet basis) LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Numbers of sows in the first parity 10 18 15 9 Colostrum, % Fat 10.3 7.5 8.5 9.0 1.1 0.855 0.310 0.121 Protein 9.1 6.2 7.5 8.9 1.0 0.608 0.482 0.054 Solids-not-fat 14.1 13.1 12.6 13.9 1.0 0.746 0.882 0.246 Lactose2 3.2b 4.2a 3.2b 3.4ab 0.3 0.097 0.029 0.089 Numbers of sows in the second parity 20 18 14 14 Colostrum, % Fat 7.9 7.5 7.1 8.0 0.6 0.818 0.790 0.341 Protein 9.9 10.5 10.4 9.7 0.8 0.803 0.997 0.341 Solids-not-fat 14.4 14.8 14.9 14.4 0.6 0.977 0.949 0.404 Lactose 2.9 2.8 3.0 3.1 0.1 0.172 0.790 0.278 Milk, day 18 of lactation, % Fat2 8.4b 8.4b 9.7a 7.4b 0.4 0.625 0.014 0.014 Protein 4.5 4.5 4.7 4.4 0.1 0.821 0.221 0.251 Solids-non-fat 11.6 11.7 11.6 11.5 0.1 0.539 0.916 0.725 Lactose 5.2 5.3 5.0 5.2 0.1 0.317 0.286 0.495 LS10 LS13 P-value1 Item LL21 LL27 LL21 LL27 SEM LS LL LS × LL Numbers of sows in the first parity 10 18 15 9 Colostrum, % Fat 10.3 7.5 8.5 9.0 1.1 0.855 0.310 0.121 Protein 9.1 6.2 7.5 8.9 1.0 0.608 0.482 0.054 Solids-not-fat 14.1 13.1 12.6 13.9 1.0 0.746 0.882 0.246 Lactose2 3.2b 4.2a 3.2b 3.4ab 0.3 0.097 0.029 0.089 Numbers of sows in the second parity 20 18 14 14 Colostrum, % Fat 7.9 7.5 7.1 8.0 0.6 0.818 0.790 0.341 Protein 9.9 10.5 10.4 9.7 0.8 0.803 0.997 0.341 Solids-not-fat 14.4 14.8 14.9 14.4 0.6 0.977 0.949 0.404 Lactose 2.9 2.8 3.0 3.1 0.1 0.172 0.790 0.278 Milk, day 18 of lactation, % Fat2 8.4b 8.4b 9.7a 7.4b 0.4 0.625 0.014 0.014 Protein 4.5 4.5 4.7 4.4 0.1 0.821 0.221 0.251 Solids-non-fat 11.6 11.7 11.6 11.5 0.1 0.539 0.916 0.725 Lactose 5.2 5.3 5.0 5.2 0.1 0.317 0.286 0.495 1LS, litter size; LL, lactation length. 2Within a row, means lacking a common superscript differ (P < 0.05). Open in new tab Discussion Genetic selection and improvement in management have resulted in a gradual increase in total number of piglets born throughout these years. A sow currently gives birth to 10 to 16 piglets per litter and 25 to 30 pigs per year (Kim et al., 2013). More piglets per litter require greater milk production to support their growth. Litter size at the beginning of lactation basically determines the number of functional mammary glands throughout the lactation period. Accordingly, there is a strong linear relationship between milk production and litter size (Elsley, 1971; King et al., 1989), simply because more functional mammary glands can produce a greater amount of milk. Our results are consistent with what Kim et al. (1999) found that sows with a larger litter size had a greater increase in litter weight but had lower growth of individual pigs than sows with the smaller litter size. However, primiparous sows with a larger litter size require additional nutrients for milk production and mammary growth (Pettigrew, 1993; Kim et al., 1999), and can encounter a severer negative balance of energy and protein during lactation (Boyd et al., 2000). The present experiment indicated that the primiparous sows only consumed 4.5-kg lactation feed per day as compared with 7.2-kg lactation feed per day in the second parity. The amount of lactation feed which is consumed by primiparous sows is not optimal to provide adequate nutrients (Touchette et al., 1998). Therefore, sows with a larger litter need to mobilize more body reserves to fill in this large nutrient gap. In the present experiment, sows lost an additional 3% farrowing weight (7.8 vs. 10.8% of farrowing body weight) and an additional 6.0% body protein (gaining 1.8 vs. losing 4.2% of farrowing body protein) during the first lactation when litter size increased from 10 to 13 piglets. The result of increased weight loss with increased litter size is similar to what Rydhmer et al. (1992) found. The range of the predicted body protein loss is similar to what Touchette et al. (1998) estimated (a range from 0.40 to 1.48 kg for a 17-d lactation). However, the sow reproductive performance that is characterized by weaning-to-estrus interval, farrowing rate, and second litter size is compromised when body protein and lipid in the first parity are not properly managed (Vesseur et al., 1994; Boyd et al., 2000; Thaker and Bilkei, 2005). In this case, the infertility of sows is related to the reduced ovarian follicle development and embryo survival (Aherne and Williams,1992; Foxcroft, 1992; Clowes et al., 2003b). Nevertheless, the present experiment indicated that the additional body tissue mobilization due to increased litter size did not affect the total born, born alive, and birth weight in the second parity. This could a result of greater farrowing body weight and body protein mass in the current experiment as compared with what Clowes et al. (2003a) reported. The advantage of a large body mass is obvious. The body weight loss in the current study is relatively smaller than the breakpoint (7.5% reduction in body weight during the first lactation) reported by Vesseur et al. (1994); the protein loss in the current study was relatively smaller than the breakpoint (12% loss of parturition protein mass) reported by Clowes et al. (2003a). Similarly, as Boyd et al. (2000) illustrated, a 4-kg body protein loss represented 16.6% of total protein mass for 165-kg sows (farrowing weight) but only 12.1% for 195-kg sows. Subsequently, the weaning weight in the current study was also greater than that reported by Clowes et al. (2003a,b). As Williams and Mullan (1989) suggested, a weaning weight of primiparous sow larger than 150 kg is required to minimize the weaning-to-estrus interval, especially when sows are nursing the large litters. Therefore, it also suggests that a larger initial body size with greater body reserves may reduce the detrimental effects of body reserves loss during lactation on the subsequent reproductive performance. However, before increasing the breeding weight, an economic analysis should be conducted to balance the cost for additional feed and the benefit of improved reproductive performance in commercial practices. However, increasing lactation length did not statistically increase weight loss, body protein and lipid loss during the first lactation. Even Willis et al. (2003) reported that sows weaned at day 24 of lactation had a greater backfat loss and a poorer body condition at weaning than sows early weaned at day 14 of lactation. Tantasuparuk et al. (2001) indicated that weight loss during lactation decreased by 0.6% per day as the lactation length increased from 17 to 34 d. Moreover, Rojkittikhun et al. (1993) showed that the primiparous sows could even gain weight from day 28 to 35 of lactation. Similarly, our results implied that the rate of body tissue mobilization slows down along with the lactation period. This is in agreement with the pattern of body tissue mobilization during lactation estimated by Boyd et al. (2000). On the other hand, lactation length may influence the subsequent reproductive performance of sows. Longer lactation length could provide more time for uterine recovery and for uterine endometrium restoration. Svajgr et al. (1974) indicated that uterine involution was not complete until 30 to 34 d of lactation and incomplete uterine involution may impair subsequent fertility. Therefore, increasing lactation length from 14 to 34 d resulted in a decreased weaning-to-service interval (Xue et al., 1993), an increased conception rate (Cole et al., 1975), an increased farrowing rate (Hays et al., 1978), and subsequently a larger litter size. Similarly, we observed that increasing lactation length from 21 to 27 d reduced the sow removal rate by 23.7%, however, increasing lactation length did not affect the litter size during the second lactation. The possible explanation for the insignificant results of born alive could also be related to the weaning weight and weaning body composition, both of which did not differ between 2 lactation length groups. As we discussed in the previous paragraph, minimum body size and body protein level at the first weaning need to be reached without compromising the reproductive ability in the rest parties (Williams and Mullan 1989; Clowes et al., 2003a). Nevertheless, LS10-LL21 was initially allotted with sows having smaller numbers of piglets total born and born alive as compared with the other groups before the cross-fostering. This imbalance in total born and born alive at the beginning of the experiment was to minimize the cross-fostering across different treatment groups, especially between the 2 litter size groups. However, the influence of this confounding effect on the results of total born and born alive in the second parity is considered less severe. Because litter phenotype in the first parity is poorly correlated to that in later parities due to the variation in farrowing BW, immune status, physiological age, chronological age, and interactions among these traits (Knol et al., 2010). Because of similar reasons, Serenius et al. (2003) recommended that the number of piglets total born in the first and later parties should be treated as separated fertility traits in breeding value estimation. Accordingly, the total born and born alive are more consistent and repeatable as sows get mature (Knol et al., 2010; Foxcroft, 2012). Therefore, in the current study, the interpretation of suckling intensity effects on the subsequent total born and born alive mainly focuses on the effects of body tissue mobilization as we discussed above, instead of genetic effects. Insufficient recovery of body reserves during gestation may compromise the second litter performance because sow may not have enough body reserves to mobilize. Boyd et al. (2000) suggested a net body weight gain of 30 to 35 kg in the second gestation, which is relatively lower than our result, is important for moderate growth and recovery of body reserves. As a result, sows with 13 piglets under a 21-d lactation length mobilized more body protein but ended with a greater estimated body protein mass at the subsequent farrowing, as compared with sows with 10 piglets. These results implied that sows with 13 piglets in the first lactation restored a greater amount of body protein during the subsequent gestation as compared with sows with 10 piglets. On the other hand, at a litter size of 10 piglets, sows with a longer lactation length during the first lactation had a 23-kg greater (tendency) weight gain during the following gestation than sows with a shorter lactation length. However, the feed intake during the second lactation was not negatively affected by the increased gestation weight gain. This result is conflicting with what O’Grady et al. (1985) found that lactation feed intake decreases with increased gestation weight gain. This may also be related to the differences of gestation feed intake, parities, and body condition between the 2 studies. Collectively, combining the effects of litter size and lactation length on gestation weight gain and protein deposition, it may imply that sows subjected to an increased previous suckling intensity underwent a subsequent compensatory growth, which was characterized by an accelerated anabolism (Wilson and Osbourn, 1960; MacPherson et al., 1969; Reese et al., 1982; Hornick et al., 2000). Sows that have mobilized a greater amount of protein reserve could restore their protein reserve greater during the subsequent gestation as compared with those which have mobilized less protein reserve. This also suggests body protein deposition in pregnant sows is relatively efficient after the muscle depletion during the previous lactation (Noblet et al., 1990). Our results also indicated that sows with a greater previous suckling intensity mobilized less lipid reserve and lost less body weight in the second lactation, as a consequence, those sows had a greater overall weight gain during the whole cycles of 2 parities. Nevertheless, the litter weight gain of sows with an increased previous suckling intensity did not decrease during the second lactation as expected. Because the responses in litter weight gain reflect the milk production, whose nutrients are originally from dietary feed intake (exogenous) and body reserves of sows (endogenous) (Pettigrew, 1993; Revell et al., 1998). The question may arise that how could sows with an increased previous suckling intensity have a reduced BW and backfat losses and still maintain the milk production at the same time? With the lactational feed intake not affected by the previous suckling intensity, sow might have a reduced maintenance requirement and increased efficiency in transporting fatty acid for beta-oxidation and in utilizing ME for milk production. This speculation is related to the accelerated pregnancy anabolism which is possibly induced by an increased previous suckling intensity. In addition, we observed that increasing the suckling intensity of a previous lactation reduced the concentration of milk fat in the subsequent lactation. Reduced body lipid loss suggested that the available substrates and energy for fatty acid synthesis in mammary glands decreased. Therefore, reduced concentration of milk fat was consistent with the result of decreased backfat loss and decreased predicted body lipid loss. However, the smaller concentration of milk fat did not significantly affect the litter performance in the second lactation. For the insignificant results of piglets total born and sow culling rate, it could be either due to missing a real effect or due to being underpowered. An insufficient sample size, small effect size, and large variation cause a less strong statistical power. Generally, the variation of sow variables is considered greater than that of nursery and grower-finisher pigs (Johnson et al., 2003). Even for pigs at the same phase, the variation for variables such as survival rate, morbidity, and culling rate is greater than that for the growth performance variables because the former ones are greatly influenced by some confounding factors such as health status, stress status, management, and genetics. The other reason is that the errors for the former variables are not normally distributed. In the present experiment, evaluating the carryover effects of treatments required a long time across 2 parities and might further increase the variation and reduce the effect size. Because of these possible variabilities mentioned above, the appropriate sample size is required to reach a sufficient statistical power. Therefore, further study with a larger sample size is needed to determine the effects of suckling intensity in the first parity on the survival rate of sows during the whole reproductive lifecycle, considering a sow can only make a positive net income after reaching parity 3. Furthermore, the effects of suckling intensity on sow lifetime productivity (lifetime born alive) are worth being validated in commercial-scale on-farm researches in the future. In conclusion, increasing suckling intensity (litter size and lactation length) of primiparous sows increased the litter weight gain whereas increasing litter size reduced piglet ADG. The performance of sows in the second lactation was not negatively affected by increasing suckling intensity of the first lactation. 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TI - Effect of suckling intensity of primiparous sows on production performance during current and subsequent parities
JO - Journal of Animal Science
DO - 10.1093/jas/skz341
DA - 2019-12-17
UR - https://www.deepdyve.com/lp/oxford-university-press/effect-of-suckling-intensity-of-primiparous-sows-on-production-yJ8euIil2p
SP - 1
VL - Advance Article
IS - 
DP - DeepDyve
ER -