Effect Of Weaning Age On Antioxidant Capacities,Growth Related Hormones And Functional Gene Expressions In Piglets

The study was aimed to evaluate the effects of weaning age on the growth performance, endocrine function, the degree of stress stimulation in piglets, and explore the molecular mechanism of weaning age on the growth of piglets, this experiments compared with the effects of weaning age on body weight, plasma biochemistry parameters, growth related hormones, serum antioxidant capacity, the expression of related-growth genes of different tissues in piglets, and so as to scientifically determine the reasonable nutrition strategy, the suitable weaning age of piglets and provide theory and practical basis for pig production. 1 Effect of weaning age on growth performance, plasma biochemistry parameters and endocrine indices of pigletsA total of 24 crossed-bred(Duroc × Landrace × Yorkshine) piglets from 8 litters with similar age and body weight were randomly assigned to 4 groups with 6 replicates in each group and 1 piglet in each replicate. The 4 groups were 14 days of age weaning group, 21 days of age weaning group, 28 days of age weaning group and 35 days of age weaning group, respectively. All piglets were fed until 42 days of age and the effects of weaning age on body weight, plasma biochemistry parameters and endocrine indices were determined. The results showed as follows: 1) the diarrhea symptoms of individual piglets were observed occasionally during the whole test period. At 42 days of age, the body weight of piglets was no significant difference among all groups(P>0.05). 2) Plasma TP and GLU contents were gradually increased with the delayed weaning age, TP contents in 35 days of age weaning groups was significantly higher than that in 14 and 21 days of age weaning group(P<0.05); GLU contents in 14 days of age weaning groups was lower than that in 28 and 35 days of age weaning groups(P<0.05); plasma CHO and TG contents at different weaning ages were no significant difference(P>0.05); plasma CK and LDH activities were gradually decreased with the delayed weaning age, CK activity in 28 and 35 days of age weaning groups was lower than in 14 and 21 days of age weaning groups(P<0.05); plasma LDH activity in 35 days of age weaning groups was lower than in 14 days of age weaning groups(P<0.05); plasma ALT, AST and ALP activities at different weaning ages was no significant difference(P>0.05). 3) Plasma GH, T3 and T4 contents of piglets were no significant difference among all groups(P>0.05); INS contents in 35 days of age weaning groups were higher than in 14 days of age weaning groups. These results indicate that early weaned can significantly affect plasma TP, GLU contents and CK, LDH activities, the changed degrees of these indexes are greater with the more early weaning age, the effect of different weaning age on growth performance and growth related hormones of piglets is no significant different. 2 Effect of weaning age on plasma antioxidant capacity in pigletsIn order to research the effect of weaning age on plasma antioxidant capacity of piglets, the plasma malondialdehyde(MDA) content of piglets and the total superoxide enzyme(T-SOD), glutathione peroxidase(GSH-Px), catalase(CAT) activities of different weaning ages piglets were determined. The results showed as follows: the MDA content in 21, 28 and 35 days of age weaning groups was lower than in 14 days of age weaning groups(P<0.05); the T-SOD and GSH-Px activities of piglets were gradually increased with the delayed weaning age, the T-SOD and GSH-Px activities of piglets in 28 and 35 days of age weaning groups were higher than in 14 days of age weaning groups(P<0.05); the CAT activity of piglets was no significant difference among all groups(P>0.05). These results indicate that weaning age can significantly affect the antioxidant capacity of piglets, and early weaning can decrease antioxidant capacity in piglets. 3 Effect of weaning age on the expression of different tissues growth related genes in pigletsAccording to the above experimental design, the liver and muscle samples were collected, and the expression of growth related genes were analysed. 1)At 42 days of age, the expression of liver GHR m RNA and IGF-Ⅰ m RNA in 28 days of age weaning groups was significantly higher than that in other three weaning group(P<0.05). The expression of liver IGF-ⅠR m RNA at different weaning ages group was no significant difference(P>0.05). 2) The expression of longissimus dorsi muscle(LD) GHR m RNA in 21 days of age weaning groups was significantly higher than that in other three weaning groups(P<0.05). The expression of LD IGF-Ⅰ m RNA in 14 days of age weaning groups was significantly higher than that in 21 days of age weaning group(P<0.05). The expression of LD IGF-ⅠR m RNA in 21 days of age weaning groups was significantly higher than that in other three weaning groups(P<0.05). 3) The expression of semitendinosus GHR m RNA in 21 days of age weaning groups was significantly higher than that in other three weaning group(P<0.05). The expression of semitendinosus IGF-Ⅰ m RNA in 14 days of age weaning groups was significantly higher than that in other three weaning groups(P<0.05). The expression of semitendinosus IGF-ⅠR m RNA in 21 days of age weaning groups was significantly higher than that in other three weaning groups(P<0.05). 4) The expression of cardiac muscle GHR m RNA at different weaning ages group was no significant difference(P > 0.05). The expression of cardiac muscle IGF-Ⅰ m RNA in 35 days of age weaning groups was significantly higher than that in 14 and 21 days of age weaning groups(P<0.05). The expression of cardiac muscle IGF-ⅠR m RNA in 21 days of age weaning groups was significantly higher than that in other three weaning groups(P<0.05). 5) The protein contents of liver GHR and IGF-Ⅰ in 28 days of age weaning groups was significantly higher than that in other three weaning group(P<0.05). The protein contents of liver IGF-ⅠR at different weaning ages group was no significant difference(P>0.05). 6) The protein content of LD GHR and IGF-ⅠR in 21 days of age weaning groups was significantly higher than that in 14, 28 and 35 days of age weaning group(P < 0.05). The protein content of LD IGF- Ⅰ in 14 days of age weaning groups was significantly higher than that in 21 days of age weaning group(P<0.05). 7) The protein content of semitendinosus GHR and IGF-ⅠR in 21 days of age weaning groups was significantly higher than that in 14, 28 and 35 days of age weaning group(P<0.05). The protein content of semitendinosus IGF-Ⅰ at different weaning ages group was no significant difference(P > 0.05). The results indicate that weaning age can significantly affect the expression of liver and muscle growth related genes. Compared with the liver GHR m RNA and protein expression, the effect of weaning age on the expression of muscle GHR is different. The effect of weaning age on GHR m RNA, IGF-Ⅰ m RNA and IGF-ⅠR m RNA of LD and semitendinosus are similar, but the effect of weaning age on IGF-Ⅰ m RNA of cardiac muscle and that of LD and semitendinosus are different. The effect patterns of weaning age on IGF-ⅠR m RNA of LD, semitendinosus and cardiac muscle are similar, and the effect patterns of weaning age on GHR and IGF- Ⅰ R protein contents of LD and semitendinosus are similar.