Genetics and environmental trends in growth performance of Horro (Zebu) and crosses of Holstein Friesian and Jersey cattle breeds

Phenotypic, genetics and environmental trends of birth (BW), weaning (WW) and one year weight (YW), and average daily gain were considered on data collected from Horro cattle and their crosses during the year 1980-2008. Estimated breeding value (EBV) of all animals were generated from a univariate model analysis by the general linear mixed model by residual maximum likelihood (ASREML) while least square means for annual breeding values was calculated by the General Linear Model procedure of the statistical analysis systems (SAS). Direct heritability estimates from bivariate analyses in the present study were 0.61, 0.34 and 0.42 for BW, WW, and YW, respectively. The overall mean predicted breeding value for birth, weaning and one year weight were 0.11±0.06 kg, 0.13± 0.09 kg and1.2 ±1.4 kg, respectively. The results shown that breeding value trends have been improving and there was about 0.016 kg, 0.031 kg, 0.14 kg genetic gain in BW, WW and YW per year. The negative phenotypic and environmental trends were more pronounced for weaning weight and pre-weaning average daily gains in this study.  Therefore, selection of in Horro and their crosses at one year weight would be suggested from present result due to high breeding annual value, high genetic correlation and positive environmental regression value.   Key words: Breeds genetics, environment, trends.