Genet. Sel. Evol.
Volume 36, Number 5, September-October 2004
|Page(s)||563 - 576|
Bayesian segregation analysis of milk flow in Swiss dairy cattle using Gibbs samplingHoucine Ilahi and Haja N. Kadarmideen
Statistical Animal Genetics Group, Institute of Animal Sciences, Swiss Federal Institute of Technology, ETH-Zentrum, Universitätsstrasse 65, 8092 Zurich, Switzerland
(Received 16 February 2004; accepted 21 May 2004)
Abstract - Segregation analyses with Gibbs sampling were applied to investigate the mode of inheritance and to estimate the genetic parameters of milk flow of Swiss dairy cattle. The data consisted of 20 4397, 655 989 and 40 242 lactation records of milk flow in Brown Swiss, Simmental and Holstein cattle, respectively (4 to 22 years). Separate genetic analyses of first and multiple lactations were carried out for each breed. The results show that genetic parameters especially polygenic variance and heritability of milk flow in the first lactation were very similar under both mixed inheritance (polygenes + major gene) and polygenic models. Segregation analyses yielded very low major gene variances which favour the polygenic determinism of milk flow. Heritabilities and repeatabilities of milk flow in both Brown Swiss and Simmental were high (0.44 to 0.48 and 0.54 to 0.59, respectively). The heritability of milk flow based on scores of milking ability in Holstein was intermediate (0.25). Variance components and heritabilities in the first lactation were slightly larger than those estimates for multiple lactations. The results suggest that milk flow (the quantity of milk per minute of milking) is a relevant measurement to characterise the cows milking ability which is a good candidate trait to be evaluated for a possible inclusion in the selection objectives in dairy cattle.
Key words: segregation analysis / Bayesian method / major gene / milk flow / Swiss cattle
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© INRA, EDP Sciences 2004