كليدواژه :
Selection Index , breeding Goal , هدف اصلاح نژاد , productive system , سيستم توليد , Economic value , ضرايب اقتصادي , Iranian Holstein , گاو هولشتين
چكيده لاتين :
Useing economic value estimates of milk yield, milk fat percentage and herd life, as traits of breeding goal and their genetic and phenotype parameters, for Iranian Holstein cows, seven selection indices were studied. First index included the information of breeding goal traits, second to fourth index included milk yield, milk fat percentage and one of the type characters (Rear Udder Height, Front Teats Placement and Front Udder Attachment ,respectively) as correlated traits with herd life, fifth index included production traits, and all of three type characters, sixth and seventh which were reduced indices, included milk yield and fat percentage and just milk yield, respectively. Economic values estimated under maximum profit and minimum cost interests, and input limitation for situations of years 1975 and 2000. Genetic gain in breeding goal and selection accuracy were estimated for different indices and two kind of interests and economic situations in two different years.The fifth index that have the highest number of traits and the seventh index that had the fewest number of characters, resulted in the highest and the least gain, respectively. The ranking of selection accuracy of these indices showed the same pattern, too.Those indices in which type characters were used instead of herd life ( indices 2,3,4 and 5), resulted in higher genetic gain. Effect of change in breeding policy for herd life, in productive -- management parameters and in prices on selection indices coefficients and their genetic gain, were investigated. Results showed that change in breeding direction in one character, had no effect on the ranking of indices. The index number 5, as having the most amount of information, made higest genetic gain. Change in production - management parameters and prices, didnʹt change the ranking of indices (except for one index). Despite of great changes in economic values in all cases, the index that had the highest number of traits, led to the highest genetic gain, and optimum selection index was stable at change of environmental situations of production system.
