PSIV-A-8 - Effect of piglet birth weight and castration age on growth performance, hematological parameters, and blood malondialdehyde levels in suckling period

Abstract: This study was conducted to investigate the effect of piglet birth weight and castration age on growth performance, hematological parameters, and antioxidant status of suckling pigs. A total of 32 male piglets from 8 sow litters with 10–14 piglets were used. At birth (d 0 of age), sow litters were randomly assigned to 2 castration age treatments (d 4 and 9 of age; initial body weight: 1.40 ± 0.24 and 1.49 ± 0.33 kg, respectively) based on litter size and weight. Then, male piglets were assigned to low-birth weight (< 1.3 kg; 0.8-1.3 kg; initial body weight: 1.20 ± 0.15 kg) and high-birth weight ( >1.5 kg; 1.5-2.2 kg; initial body weight: 1.69 ± 0.19 kg). Therefore, four treatments were: 1) d4-HBW: high-birth weight pigs castrated on d 4 of age (n = 6), 2) d9-HBW: high-birth weight pigs castrated on d 9 of age (n = 12), 3) d4-LBW: low-birth weight pigs castrated on d 4 of age (n = 9), and 4) d9-LBW: low-birth weight pigs castrated on d 9 of age (n = 5). Growth performance was recorded at d 0, 4, 9, and weaning (20.6 ± 0.8 d of age). Blood samples were collected from 4 pigs per treatment for complete blood count and plasma malondialdehyde analyses. There were no interactions observed in any measurements. There were no significant differences (P > 0.60) in weaning weight (5.28 and 5.47 kg for d 4 and 9 of castration age, respectively) and overall growth rate (0.189 and 0.191 kg/d, respectively) during the suckling period between the castration age groups. Pigs castrated at d 4 of age had lower hemoglobin levels (P< 0.05; 120.6 and 127.3 g/L, respectively) but higher basophil percentage (P = 0.07, tendency; 0.85 and 0.50%, respectively) than those castrated at d 9 of age. Plasma malondialdehyde levels decreased by increasing castration age from d 4 to 9 of age (P< 0.05; 13.39 and 9.60 µM, respectively). The HBW pigs had greater average daily gain (P < 0.05; 0.229 and 0.151 kg/d for the HBW and LBW pigs, respectively) in the overall suckling period than the LBW pigs, resulting in 2.04 kg heavier weaning weight (P < 0.05; 6.39 and 4.35 kg, respectively). The HBW piglets had lower hemoglobin (P < 0.05; 119.8 and 128.1 g/L, respectively) and hematocrit (P = 0.06, tendency; 37.98 and 41.81%, respectively) levels at weaning. In conclusion, the castration age did not affect growth performance of suckling pigs until weaning, while late castration resulted in greater hemoglobin levels and lower oxidative stress levels at weaning than early castration. The HBW piglets grew faster and had heavier weight and lower hemoglobin and hematocrit levels at weaning than the LBW piglets.