Selection strategies for fertility traits of Holstein cows in Iran

Efficient reproductive performance is an important prerequisite for sustainable dairy production systems. Moreover, reproductive performance has become one of the most important functional traits in the dairy cattle industry, because of its economic importance, as well as its effect on animal welfare. The objective of present study was to evaluate the consequence of alternative selection strategies to improve fertility performance of Holstein cows in Iran. The traits milk production (. M), number of inseminations per conception (INS), days from calving to first insemination (DFS), maternal calving difficulty (MCD) and direct calving difficulty (DCD) were included in an aggregate genotype (. H). The selection indices in each strategy were a different combination of fertility traits and milk production. Although fertility traits were included in the aggregate genotype, in the first selection strategy, in which selection was based on milk production, unfavorable genetic gain for fertility traits occurred. In the second strategy, in which genetic gain for milk production was restricted to zero, in comparison to the other strategies, the genetic gains for profit and fertility traits were lowest and highest, respectively. In the third strategy, in which genetic gain for fertility traits was restricted to zero, the genetic gains for milk production and profit differed little compared to the first strategy. Favorable genetic gains were obtained for both fertility traits and milk production in the fourth strategy, in which proportional restriction was used. Although the genetic gain for milk production in this strategy was lower than in the first strategy, genetic gain for profit showed slightly differed. © 2012 Elsevier B.V.