荷斯坦牛皮肤褶皱厚度及体况评分性状遗传分析

本研究通过对荷斯坦牛颈侧部、肋部和后乳房基部皮肤褶皱厚度（分别简称为颈部、肋部和乳房皮褶厚）及体况评分（body condition score，BCS）进行大群测定，旨在探究荷斯坦牛不同部位皮肤褶皱厚度和BCS的群体特征，并建模估计荷斯坦牛不同部位皮肤褶皱厚度及BCS的遗传参数。本研究于2015—2020年夏季测定了北京地区12个规模化牧场10 915头泌乳荷斯坦牛的皮肤褶皱厚度，同时对测定牛群进行了体况评分，使用单性状和四性状动物模型分别对颈部皮褶厚、肋部皮褶厚、乳房皮褶厚和BCS进行遗传分析并估计遗传参数，并计算了上述4个性状与奶牛寿命和繁殖等重要功能性状之间的近似遗传相关。结果显示，荷斯坦牛乳房皮褶厚、颈部皮褶厚、肋部皮褶厚和体况评分分别为（7.49±1.45） mm、（7.27±1.34） mm、（11.74±1.90） mm和（2.94±0.79）；乳房皮褶厚和颈部皮褶厚为中等遗传力性状，遗传力分别为0.11和0.15；肋部皮褶厚和体况评分为中高遗传力性状，遗传力分别为0.28和0.22；不同部位的皮褶厚之间存在中高遗传相关，颈部和肋部皮褶厚之间的遗传相关最高（0.69），颈部和乳房皮褶厚之间的遗传相关最低（0.21）；BCS与不同部位皮褶厚之间遗传相关的差异较大，BCS与颈部、肋部皮褶厚之间为正遗传相关（0.28、0.13），BCS与乳房皮褶厚之间为负遗传相关（-0.25）；体况评分和皮褶厚性状与部分重要功能性状之间存在中等遗传相关。本研究对奶牛3个部位的皮肤褶皱厚度和BCS性状进行了遗传分析，研究获得的遗传参数有助于通过皮肤褶皱厚度和BCS理解奶牛体脂沉积的遗传基础，助力我国奶牛的平衡育种。

Genetic Analysis on Skinfold Thickness and Body Condition Score Traits in Holstein Cows

In this study, the skinfold thickness over the neck (STN), rib (STR) and udder (STU) of Holstein cows (referred to as neck, ribs and breast skinfold thickness, respectively) and body condition score (BCS) were measured in a large population. The purpose was to explore the population characteristics of skinfold thickness in different body positions and BCS, and to estimate the genetic parameters of skinfold thickness in different body positions and BCS of Holstein cows by modeling. The STN, STR, STU and BCS of 10 915 lactating Holstein cows from 12 dairy farms were measured in summer from 2017 to 2020. The single-trait and four-trait animal models were employed to perform genetic analysis, and heritabilities and genetic correlations for STN, STR, STU and BCS were obtained. Furthermore, the approximate genetic correlations between skinfold thickness, BCS and important functional traits (longevity and reproduction traits) were calculated. The results showed that the STU, STN, STR and BCS in Holstein cows were (7.49±1.45) mm, (7.27±1.34) mm, (11.74±1.90) mm and (2.94±0.79), respectively. There were moderate heritabilities for STN (0.15) and STU (0.11), and moderate to high heritabilities for STR (0.28) and BCS (0.22). The moderate to high genetic correlations among the skinfold thickness over the different body positions were found, ranging from 0.21 (STN and STU) to 0.69 (STN and STR). There was a large variation for genetic correlations between BCS and skinfold thickness over the different body positions, ranging from -0.25 (BCS and STU) to 0.28 (BCS and STN). The moderate genetic correlations between skinfold thickness, BCS and some functional traits were found. In this study, the genetic analysis on skinfold thickness and BCS traits were performed, and the heritabilities and genetic correlations for skinfold thickness over the different body positions and BCS were estimated. The results from the current study could help us understand the genetic foundation for fat deposition in dairy cattle, and was beneficial for balance breeding in Chinese Holstein population.