Joint estimation of genetic parameters for daily recorded milk yield and body weight in first lactation Holstein cows. T. Tribout1, S. Minery1,2, B. Dassé3, D. Saunier4, V. Ducrocq1, D. Boichard1 The objective of the study was to jointly estimate the genetic parameters for daily recorded milk production (MY24) and body weight (BW) in first lactation Holstein cows. A total of 329,334 MY24 and BW phenotypes recorded from day in milk (DIM) 1 to 335 on 2,207 primiparous Holstein cows, calving from October 2013 to April 2017, were analyzed. The data came from 36 commercial dairy farms equipped with milking robots with automatic weighing platform, members of the Bretagne Conseil Elevage Ouest network. The variance components, heritability and genetic correlations for MY24 and BW were estimated using a bi-variate random regression test day model, where additive genetic and permanent environmental effects for the lactation and body weight curves were modeled using orthogonal Legendre polynomials of the second and fifth orders, respectively. The heritability for MY24 increased from 0.02 to 0.26 from DIM 1 to DIM 300, and then decreased. The heritability for BW increased from 0.26 (DIM 1) to 0.42 (DIM 100), remained quite stable until DIM 322, and then declined. The genetic correlations between BW and MY24 were positive. They were very low (<0.20) in early lactation, but larger after DIM15. This preliminary study will be repeated on a larger dataset and extended to multiparous cows, to evaluate the possibility of uncoupling body mobilization in early lactation from milk production. Keywords: random regression, genetic parameters, milk yield, body weight, dairy cow, milking robots
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Electronic Poster Session - Biology & Species - Bovine (dairy) 2, , 489, 2018
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