Genetic Parameter Estimation Of Growth Traits And Breeding Target Determination Of Angus Cattle In Ningxia

In this study,The measured data were from the weight and body size traits of Angus cattle in Ningxia from 2016 to 2019,the genetic parameters of body weight and body size in five growth stages of Angus cattle were estimated by using the method of DMU_AI module of DMU software and constrained maximum likelihood(ai-reml)combined with the algorithm of expectation maximization(EM)and the multi character animal model;Based on the existing breeding and production conditions of Angus cattle,the marginal benefit and economic importance of target traits are calculated by the difference method to determine the breeding target of Angus cattle.The results are as follows:1.The heritability estimates of body weight,body height,body length,Chest girth,abdomen circumference,Shin circumference and Cross height at the primary stage were 0.4929,0.7097,0.6586,0.5610,0.5174,0.6212 and 0.7121,respectively.The phenotypic correlation coefficients of each trait ranged from-0.0290 to 0.8263,and the genetic correlation coefficients ranged from-0.2920 to 0.8934;The estimated heritability of body weight,body height,body length,Chest girth,abdomen circumference,Shin circumference and Cross height at 6 months of age were 0.3847,0.4498,0.4013,0.7972,0.5887,0.6682 and 0.4573,respectively.The phenotypic correlation coefficients of all traits at 6 months of age ranged from 0.2172 to 0.6693,and the genetic correlation coefficients ranged from 0.1241 to 0.8148.The estimated heritability values of body weight,body height,body length,Chest girth,abdomen circumference,Shin circumference and Cross height at 12 months of age were 0.5031,0.4539,0.5962,0.5990,0.5464,0.7410 and 0.5312,respectively.The phenotypic correlation coefficients ranged from 0.3302 to 0.7324,and the genetic correlation coefficients ranged from 0.0747 to 0.7303.The estimated heritability values of body weight,body height,body length,Chest girth,abdomen circumference,Shin circumference and Cross height at 18 months were 0.5185,0.5565,0.7144,0.6580,0.8251,0.6490 and 0.5011,respectively.The phenotypic correlation coefficients ranged from 0.3996 to 0.8482,and the genetic correlation coefficients ranged from 0.2093 to 0.7539.The estimated heritability values of body weight,body height,body length,Chest girth,abdomen circumference,Shin circumference and Cross height at 24 months were 0.6925,0.5303,0.7155,0.7141,0.7988,0.6316 and 0.4432,respectively.The phenotypic correlation coefficients ranged from 0.1587 to 0.7901,and the genetic correlation coefficients ranged from 0.3097 to 0.9697.3.Three kinds of breeding target traits(growth and development traits,reproduction traits and carcass traits)were determined to include eight traits,namely,birth weight,weaning weight,12-month-old weight,18-month-old weight,growth ability,age of first birth,calving interval and carcass quality.The marginal benefits of each trait were 28.40 yuan,24.61 yuan,17.96 yuan,15.35 yuan,1.72 yuan,3.63 yuan,6.01 yuan and 960.00 yuan in turn.Its relative economic importance is 3.76%,10.31%,28.40%,22.41%,0.16%,0.24%,8.45%and 26.27%respectively,The relative economic importance of growth and development traits,reproduction traits and carcass traits was 65.04%,8.69%and 26.27%,respectively,which was similar to 7:1:3The results will provide an important theoretical basis for the selection of Angus cattle core group and the establishment of a reasonable selection and breeding program.