Genetic Parameter Estimation Of Litter Uniformity And Correlation Study Of Serum Level Of Cortisol And Insulin And Piglets Birth Weight

Piglets uniformity has caused great negative impact on pig industry,and cortisol and insulin were related with birth weight. In this study, REML(restricted maximum likelihood) method with an animal model were used to estimate the genetic parameters of 8 reproductive traits in the Large White pig; GLM program of was used to analyze the effects of a particular year, mating season and fetal times on reproductive traits; Duncan method was used to conduct the multiple comparison of reproductive traits between each fixed effect; radioimmunoassay was used to test the cortisol and insulin levels in serum of different birth weighty piglets. This study could provide data support on genetic force of piglet uniformity for breeding operations and provide important reference function for exploring the effects of cortisol and insulin on birth weight.1. Genetic parameters estimation of piglet uniformityThe study used five models to estimate the variance components and genetic parameters of CV0、CV3、TNB、NBA、NBD、TLW0、TLW3、GL of Large White. The result presented that model V is the better model than other models.Because the residual variance of model V is the least. It seemed more appropriate to estimate variance components use model Vhe results suggest that the heritability estimates of TNB, NBA, NBD, CV0, CV3, TLW0, TLW3 and GL were 0.14, 0.13, 0.07, 0.07, 0.02, 0.11, 0.08 and 0.09, respectively. The results also showed that there are remarkable positive genetic correlations between TNB and NBA(0.93), TNB and TLW0(0.61), TNB and TLW3(0.61), NBA and TLW0(0.65), NBA and TLW3(0.73), CV0 and CV3(0.65), TLW0 and TLW3(0.91); whereas TNB and CV0, TNB and CV3, CV0 and NBD exhibited small genetic correlations(0.29,0.17, 0.22, respectively).The analysis of variance on fixed effects showed that there is no significant effect of year on TNB and CV0(P>0.05) and extremely significant effect of year on the other 6 reproduction traits(P<0.01). Mating season had significant effect on CV0(P<0.05) but had no significant effect on TNB, NBA, and CV3(P>0.05). Parity had significant effect on TNB, NBA, NBD(P<0.05) and had significant effect on CV0, CV3, TLW0, TLW3 and GL(P<0.01). Litter size classification had significant effect on all the reproduction traits(P<0.01)According to the least squares means(LSM) of the reproductive traits, with the increase of parity, TNB, NBA, TLW0, TLW3 presents the same change law that they are at the lowest levels at the first parity, then gradually rise, and reach the maximum at the 3rd or 4th parity before they start to decline. The effect of the season on the reproductive traits is that the best production performance is in winter; with the litter size increasing, CV0, CV3 and NBD go up, but MBW0, MBW3 and GL decline; and with the litter size increasing, the proportion of piglets at birth weight less than 1Kg increases while that of piglets at birth weight greater than 1.8Kg goes down.2. Analysis on correlation between birth weight and serum cortisol and insulinTen flocks of Large White pigs including 40 newborn piglets were selected as the experimental samples, with 2 at low birth weight(<1.0Kg) and 2 at high birth weight(>1.2Kg) in each flock. When piglets were born, we conducted blood sampling from vena cava anterior, extracted serum by centrifugation method, and measured contents of COR and INS in the serum by radioimmunoassay.The serum cortisol in high birth weight group and in low birth weight group were 214.72(ng/ml) and 267.87(ng/ml), respectively. The serum insulin in high birth weight group and in low birth weight group were 28.67(m IU/L) and 20.92(m IU/L), respectively. There was significant difference in the contents of serum cortisol and serum insulin between two groups. There was a significant negative correlation between serum cortisol and birth weight(rg=-0.32), the correlation coefficient between serum cortisol and birth weight was 0.23 and the correlation coefficient between two groups was not significant(P=0.09). The result and provide important reference function for exploring the effects of cortisol and insulin on birth weight.