PS6-14. Effects of Pig Weaning Weight and Sex on Growth Performance, Fecal Score, and Blood Antioxidant Capacity in Early Nursery Period

Abstract This experiment was conducted to evaluate the effects of weaning weight (WW) and sex on growth performance, fecal score, and blood antioxidant parameters in nursery pigs. At weaning (19.0 ± 1.35 d of age), a total of 64 newly weaned pigs (32 barrows and 32 gilts) were allotted to two WW categories: high WW (HWW) pigs with body weight (BW) over 5.5 kg (average 6.30 ± 0.53 kg) and low WW (LWW) pigs with BW less than 5.5 kg (average 4.85 ± 0.46 kg) in eight replicate pens per treatment (4 pens of barrows and 4 pens of gilts). Pigs were fed a common corn-soybean meal-based nursery diet for 28 d post-weaning in 2 phases (d 0-14 and d 14-28 postweaning). Individual BW and pen feed disappearance were recorded weekly to calculate average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F). Fecal score was recorded daily using a 4-scale system (1=normal, 4=severe diarrhea). Blood samples were collected weekly from 1 pig per pen for the analysis of plasma malondialdehyde (MDA) and superoxide dismutase (SOD). No significant sex effects were observed in any growth performance and blood antioxidant parameters. There were no significant differences in ADG (0.068 and 0.060 kg/d for HWW and LWW, respectively) and ADFI (0.151 and 0.134 g/kg, respectively) in d 0-7 postweaning. However, the HWW pigs had greater overall ADG in d 0-28 postweaning (P 0.05; 0.316 and 0.265 kg/d, respectively). Overall ADFI in d 0-28 postweaning tended to be greater in the HWW pigs than the LWW pigs (P = 0.06; 0.558 and 0.476 kg/d, respectively), whereas G:F and fecal score were not affected by WW in the entire nursery period. Plasma MDA levels tended to be greater in the LWW pigs than in the HWW pigs at d 7 postweaning (P = 0.07; 1.98 and 1.74 µM, respectively). Plasma MDA levels at d 7 postweaning tended to have negative correlations with WW (P = 0.09, r=-0.47), ADG (P = 0.10, r=-0.45) and ADFI (P = 0.09, r=-0.48) in d 0-7 postweaning. Plasma SOD activity did not differ between WW treatments during the entire nursery period, while WW had positive correlations with plasma SOD activity at d 7 (P = 0.10, tendency; r = 0.48), d 21 (P 0.05, r = 0.55), and d 28 postweaning (P 0.05, r = 0.56). There were no correlations observed between WW and plasma MDA and SOD levels at weaning. In conclusion, although WW did not affect growth performance in the first week postweaning, greater WW was associated with increased feed intake and growth rate in the overall nursery period, without affecting feed efficiency, and correlated with enhanced antioxidant capacity and reduced oxidative stress.