奶牛体型外貌评分与产奶量的相关分析

Correlation analysis between 305 days' milk yield and conformation score traits of Chinese Holstein cattle

以西安市第二奶牛场选取的健康、泌乳正常的第3泌乳期奶牛为研究对象,随机抽取50头奶牛,测定其305d产奶量及15个体型外貌评分性状,采用相关分析方法确定整体评分及15个性状与305d产奶量之间的关系,以整体评分及15个性状为自变量,305d产奶量为依变量,采用多元回归分析法,经统计检验后,保留作用大的自变量,建立了"最优"回归方程。结果表明,整体评分与305d产奶量之间存在弱正相关,差异不显著;15个评分性状中,后房高度、后房宽度与305d产奶量呈极显著相关;乳房中隔和乳房深度与305d产奶量呈显著相关;利用这4个评分性状建立了估计305d产奶量的"最优"回归方程,通过对生产中30头牛的估测,并与实际测定值进行差异显著性检验(t-检验),差异不显著(P>0.05),表明该回归方程准确可靠;后房高度、后房宽度、乳房中隔和乳房深度是影响305d产奶量的最主要因素。

Data for this study were collected from 50 dairy cattle in the third milk period in Second Dairy Cattle Farm of Xi'an City.15 conformation traits and 305 days' yield (Y) were measured and conformation scores were calculated.The correlation coefficients were calculated.The four conformation traits as independent variables,and 305 days' yield as a dependent variable,path analysis,path coefficients (P),determination coefficients (d) and correlation index (R^2) were calculated.The results showed that 4 correlation coefficients between each udder character and the 305 days' yield were all significantly different (P<0.05).But the correlation coefficient between conformation score and the 305 days' yield was not significant (P>0.05).Hind udder height (X_10) and Hind udder width (X_11) gave predominant effects,Sept-udder (X_12) and Udder depth (X_13) gave slightly direct effect and significant indirect effect through udder girth on 305 days' yield.It was clear that the path coefficient analysis could reveal the relationship between the independent variables and the dependent variable.