关键词: 奶牛; 遗传参数; 健康性状; 平衡育种

Abstract: 【Objective】 The objective of this study was to perform a genetic analysis using farm production data to determine the genetic parameters of five common diseases in Chinese Holstein.The findings would guide the formulation of dairy cattle breeding strategies that incorporate health traits,thereby facilitating an enhancement in the health status of the dairy cattle population in China.【Method】 Quality control was performed on 230 826 calving records from 95 710 cows and 333 038 disease records from 121 811 cows,collected from 30 national dairy farms during the period of 2019 to 2022.These records were then matched and compiled into a phenotypic dataset.The phenotype for each individual cow in each calving event was defined based on the presence or absence of disease,with 0 representing healthy and 1 representing diseased.The diseases considered were mastitis (MAST),clinical ketosis (KET),retained placenta (RETP),metritis (MET),and displaced abomasum (DA).A single-trait repeatability model was used to estimate the variance components for each trait,followed by the calculation of heritability and repeatability.A two-trait repeatability model was employed to estimate the phenotypic correlation and genetic correlation between traits.Both models incorporated fixed effects for farm-year,parity,and calving season.The effect of selection on health traits was investigated by comparing the disease incidence in the offspring of bulls ranked in the top 20 and bottom 20 for estimated breeding values (EBV).This comparison was performed using a chi-square test.【Result】 The results showed that the heritability for the traits MAST,KET,RETP,MET,and DA was estimated to be 0.063±0.005,0.051±0.005,0.015±0.002,0.033±0.003,and 0.020±0.002,respectively,all of which were characterized as traits with low heritability.Genetic correlations among these traits varied from ―0.110 to 0.684,with notably strong positive correlations observed between KET and DA as well as MET and RETP.For all traits,the average incidence rate of the offspring of the top 20 bulls of EBV was significantly lower than that of the offspring of the bottom 20 bulls (P＜0.01),and the difference in incidence rate reached 2.2 to 7.4 times.【Conclusion】 In this study,all five health traits exhibited low heritability,but they could be improved by selective breeding.Thus,it’s validated to incorporate the heallth traits in Chinese Holstein genetic improvement program to achieve balanced breeding objectives.

Key words: dairy cow; genetic parameters; heallth traits; balanced breeding