The use of conformation traits to aid selection for functional cows becomes more important as once-a-day (OAD) milking for whole or part season becomes more common. In 2013, Massey University Dairy 1 farm transitioned their mixed-breed herd milked twice-a-day (TAD) to an OAD spring-calving system. All cows on the farm were scored for 14 inspector-scored type traits and four farmer-scored traits, for a total of 1,617 lactation records over seven seasons (2013-2019, 168 to 258 cows per year). Genetic parameters, breed and heterosis effects were obtained from an animal model that included the fixed effects of year of scoring and cow age at scoring, and the covariates of proportion Holstein-Friesian, heterosis between Holstein-Friesian and Jersey, and the random effects of permanent environment of cow and random additive genetic effect of animal. Stature and live weight were found to have the greatest heritability estimates (0.46 and 0.41 respectively), while leg angle and body condition score had the lowest (0.03 and 0.04 respectively). Breed had a significant effect on all type scores, with heterosis also having significant effects; this is an important consideration with the increasing importance of type scores for cows in OAD milking systems. Jersey cows had greater front udder and udder support scores than did Holstein-Friesians (P<0.05), while Holstein-Friesians had greater stature and liveweight scores (P<0.05). From this study, genetic selection for improved udder conformation would see beneficial gains over time, whilst body condition score is heritable, would not be similarly improved. Keywords: Traits other than production; once-a-day milking; genetic parameters

NW, Sneddon, DJ Donaghy, and N Lopez-villalobos

Proceedings of the New Zealand Society of Animal Production, Volume 80, Online, 51-54, 2020
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