Authors : Z. Daliri , S.H. Hafezian , A. Shad Parvar and G. Rahimi
Abstract: The aim of this study was to explore the impact of production and type traits on the functional herd life of Iranian Holstein cows using multiple regression models. The data set consisted of 896,834 registered cows from 2005 herds calving from 1971-2003. The obtained records from these cows used to estimate the correlation coefficients between THL and FHL traits using milk production and 19 linear type traits. The data set related to registered Holstein cows were provided by NABC of Iran. Parameters were estimated using univariable animal model with the restricted maximum Likelihood method. Heritability and Breeding Value were estimated using univariable analysis for milk, fat and protein yield during 305 days. Heritability for these traits was calculated 0.25, 0.23 and 0.19, respectively. The Heritability values for THL and FHL ranged from 0.04-0.03, respectively. Among type traits, teat length had the lowest (0.007) and rear teat placement had the highest heritability (0.50) values. Phenotypic correlation between FHL and stature, body depth, rump width and udder characteristics was negative, which indicates the cows with smaller body, shorter stature have longer productive life. The phenotypic correlation between FHL and feet angularity, mammary ligaments, teat length and production traits (milk and fat yield) were positive. Feet and legs along with mammary system also had a strong relationship with functional longevity. Among the linear type traits, udder traits such as teat height and rear udder width were the most important, with a strong relationship with functional herd life of cows. The type traits of stature, size and rear udder height showed the lowest relationship with functional longevity. The obtained results at the present study shoed that the improvement of production along with type traits either through genetics or management would have a positive influence on the functional longevity of cows.
Z. Daliri , S.H. Hafezian , A. Shad Parvar and G. Rahimi , 2008. Genetic Relationships among Longevity, Milk Production and Linear Type Traits in Iranian Holstein Cattle. Journal of Animal and Veterinary Advances, 7: 512-515.