Use of mixed-model methodology to estimate genetic and environmental parameters for production traits in Caracu cattle

Abstract

The objectives of this study were to evaluate environmental effects and to estimate genetic parameters of productive traits of Caracu cows. The data consisted of milk production records of cows calving between 1983 and 1990. The production traits were: milk yield per lactation (PTL), first lactation milk yield (PLP), and daily milk yield during the first interval between calving (PLIEP). The number of observations, least-squares means and standard error for traits analysed were: (2792) 1547.7±34.0 kg for PTL; (1323) 1356.8±30.3 kg for PLP; and (729) 3.5±0.10 kg for PLIEP. The fixed effects of month and year of calving and sex of calf were significantly (P<0.01) for productive traits. Heretability estimates, obtained by Derivative Free Restricted Maximum Likehood (DFREML), were PLT, 0.34±0.08; PLP, 0.55±0.08; and PLIEP, 0.22±0.11. Estimate of repeatability for milk yield was 0.42±0.01.