关键词: 奶牛, 长寿性, 遗传评估, 遗传相关, 遗传标记, 遗传选育

Abstract:

Longevity is an important functional trait in dairy cattle. In addition to yield traits, longevity is more economically important than other traits in dairy breeding. The characteristics of longevity include low heritability, unfollowing normal distribution and performance later, hence longevity is the most difficult trait to select in dairy breeding. Since the 1950s, dairy breeders have begun to pay attention to longevity traits. Now, researches on longevity traits have continued. After the 1990s, longevity has been included in total selection index in many countries. However, longevity traits currently are not included in China Dairy Performance Index (CPI), and the study on longevity traits is also in its infancy in China. This review presented the trait definitions, methods of genetic evaluation, relationships between other traits, genetic makers, and selection strategies on longevity traits to systematically introduce its research and application in dairy industry. The complex relationships between longevity and other traits were described by summarizing the genetic correlation coefficients reported by many studies. The selection strategies for longevity traits in the various countries with developed dairy industry were highlighted by summarizing information collected from their dairy breeding program. Furthermore, this review also summarized the studies on longevity traits in dairy cattle in China. Longevity traits had various definitions, and there were various models used to preform genetic analysis, including linear model, threshold model, survival model and random regression model. There were low to moderate genetic correlations between longevity and other traits, including yield, linear type, fertility, health and workability traits, in which the higher genetic correlations were found between longevity and linear type traits in udder system. Generally, dairy cows with better performance on fertility and health traits were better on longevity. Among different populations, there were some differences on relationships between longevity and other traits, which were largely influenced by selection goals of current population. The total selection indexes in many countries included longevity. In addition to using direct longevity to select it, the indirect selection methods were also used in many countries. Udder system, strength, rump angle, feet and leg system, and mastitis resistance were comment traits used to indirect selection. Many genetic markers associated with longevity have been found in various populations, most of which were in genetic regions that have been reported to be associated with traits such as reproduction, disease and body type. Finally, this review also proposed the necessities of collecting longevity data, estimating genetic parameters, locating genetic markers, exploring evaluation model and selection strategy in China dairy cattle population.

Key words: longevity, genetic evaluation, genetic correlation, genetic maker, genetic selection, dairy cattle