Genetic analysis of the growth rate of Israeli Holstein calves.

Weight of male and female Israeli Holstein calves and yearling gain were analyzed on 285 800 records from 105 935 animals from 458 herds recorded between 1994 and 2007. The difference between the sexes increased until around 400 days, at which point the difference between males and females was 110 kg. Yearling gain, defined as 365 × (weight - 35)/age + 35, was greatest for males at approximately 300 days and for females at 225 days. Yearling gain of male and female calves were highly correlated genetically; thus records from both sexes were combined into a joint genetic analysis. Heritability and repeatability were 0.33 and 0.73 in the analysis of both sexes, and similar in the single-sex analyses. Yearling gain is also highly correlated genetically with various measures of mature cow size. Yearling gain was positively correlated with milk, fat, protein production and somatic cell score, but negatively correlated with fertility and cow survival. Yearling gain was also positively correlated with both the sire and maternal grandsire effects on dystocia, but not with calf mortality. The genetic trend for yearling gain was 0.16 kg/year, while phenotypic trends for first and last weighings were both negative.