Genetic relationship of conformation traits with lactose percentage and urea concentration in milk of Polish Holstein?Friesian cows

摘要

The objective of this study was to estimate genetic correlations of lactose percentage and ureaconcentration in milk with conformation traits related to udder and legs of Polish Holstein?Friesiancows. Data consisted of 5,813 test?day records and type scores of 791 primiparous cows. The analysisinvolved two descriptive traits (udder, feet and legs, scored from 50 to 100) and 11 linearly scored traits(describing udder: fore udder height, rear udder height, central ligament, udder depth, udder width,fore teat placement, teat length, rear teat placement; describing legs: rear legs – side view, foot angle,rear legs – rear view; on a scale of 1 to 9). Genetic correlations were calculated based on (co)variancesestimated using the Bayesian method via Gibbs sampling and the multitrait animal model. Geneticcorrelations between lactose content and conformation traits ranged from ?0.18 to 0.23, while thosebetween milk urea concentration and conformation traits ranged between ?0.02 and 0.43, respectively.Absolute values of average genetic correlations with daily lactose percentage exceeded 0.15 only forudder (descriptive trait) and several linearly scored traits, i.e. central ligament, udder depth, rearteat placement, and rear legs – rear view. Milk urea content was weakly or moderately geneticallycorrelated with six type traits: udder, and five linearly scored traits: fore udder height, centralligament, udder width, teat length, and rear legs – side view. Absolute values of genetic correlationsbetween these traits exceeded 0.15. Our results showed that type traits connected with udder weremore highly genetically correlated with both lactose and milk urea contents than type traits describinglegs. It meant that an increase in both lactose percentage and urea concentration in milk might beexpected as an indirect response to selection for better udder, whereas selection for improvement oflegs would not affect lactose percentage and milk urea content.