The aims of this study were to compare 305-day or less than 305-day milk yield estimated by the test interval method and the Wood model method, and to estimate genetic parameters of 305-day or less than 305-day milk yield estimated by test interval method (MY) and Wood model method (WMY), lactation length (LL), fat percentage (FP) and protein percentage (PP) from first lactation dairy cattle raised in Thailand. The data comprised 11,753 monthly test-day records from 1,300 first lactation of purebred Holstein-Friesian (HF) and crossbred HF with local or zebu animals. Genetic parameters were estimated by univariate and bivariate linear mixed animal model using ASReml-R. The fixed effects were herd, breed group, year of calving, season of calving and the interaction between year and season of calving and the random effects were animal and residual. The estimated heritabilities for MY, WMY, LL, FP and PP were 0.22 ± 0.06, 0.23 ± 0.06, 0.09 ± 0.04, 0.16 ± 0.05 and 0.47 ± 0.07, respectively. The genetic correlations were high between two milk yield estimates (MY and WMY), and moderate to high between milk yield and LL (0.51 to 0.78), and low to moderate among milk composition (FP and PP) and LL (-0.17 to 0.42). Overall the heritability estimates of all the traits analysed were moderate to high except LL, these indicated that most traits in this herd can be improved by selective breeding. Keywords: milk traits, lactation length, wood model

Santi Pangmao, Peter Thomson, Mehar Khatkar

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Electronic Poster Session - Biology & Species - Bovine (dairy) 2, , 797, 2018
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