麦洼牦牛184天乳量与相关性状的线性关系

对１３４头成年麦洼母牦牛犊牛初生重、最高月产奶量、乳脂率以及产犊前６个月时的体重、体高、体长、胸围、评分８个性状与１８４天产奶量的直线相关及上述８个性状与后者的偏回归和标准偏回归关系作了分析。结果显示，最高月产奶量与１８４天产奶量有明显的直线正向关系（ｐ＜０．０１），两者的偏回归关系为明显的同向绝对量增长态势（ｐ＜０．０１），前者对后者产生较大的正直接作用（ｐ＜０．０１），对后者的相对决定程度最高，是最为重要的早期选择性状。发现乳脂率与１８４天产奶量在线性范畴内相对独立，此结果区别于普通奶牛，可作为该二性状同时正向选择的科学依据，体重、体长、胸围分别与１８４天产奶量呈明显的正直线相关（ｐ＜０．０５或ｐ＜０．０１），可作为产奶量趋向性预测的早期信息。

The Linear Relation between 184-day Milk Yield ofMaiwa Female Yaks and its Correlative Traits

The correlation is analysed between 184 -day milk yield of 134 Maiwa female yaksand their eight traits, that is, calf birthweight, the highest monthly-milk yield, the butter-fatpercentage, bodyweight, the height at wither, body length, heartgirth and the score, and also thepartial regression and standard peial regression of the above traits to milk yield. The bodyweight, theheight at wither, the bodylensth, the heartgirthand the seore are measured 6 months before calving.The results reveal that there is a positive straight line correlation between the highest monthly-milkyteld and 184-day milk yieid (p<0. 01 ) , and the panial-resression relation between the foamer andthe latter is very obvious(p<0. 01). There is a tendency of synchronous increase in them, and theformer plays a direct role in the increase of the latter(p<0. 01 ) and the coefficient of detennination ofhighest monthly-milk yield is higher than other traits. Therefore, it is the most important character forthe selection in early stase. It has been discovered that the relation between milkfat and 184-daymilk yield is relatively independent in linear relation. This result is different from other ordinary milkcows, so that the two traits can be used as a scientific basis for synchronisni selection. Each of thebodyweight, the bodylensth, and the heartgirth presents a positive straight line correlation with the184-day milk yield (p< 0. 05 or p<0. 01). They are able to act as an early inforniation of theforecast for the trend of milk yield.