GENETIC-PARAMETERS FOR BODY-WEIGHT AND GROWTH IN DUTCH BLACK-AND-WHITE REPLACEMENT STOCK

Genetic parameters for body weight and growth were estimated using data on 631 Black and White growing dairy heifers, from 60 sires, and born between 1982 and 1990. Body weights were collected monthly and by linear interpolation adjusted to weights at 10, 20, 30, 40 and 50 weeks of age, at breeding, at 26 and 13 weeks before calving and at calving. Also weight at 2 days after calving was recorded. Heifers were fed a restricted amount of concentrate and ad libitum roughage. Data were analyzed using an animal model, considering year-season, parity of dam, and genetic group as fixed effects. Average age and weight at calving were 733 days and 508 kg, respectively. Unadjusted average daily gains from birth to 50 weeks of age and from breeding to calving were 731 (SD 68) and 527 (SD 107) g day-1, respectively. Heifers born from second and third parity dams were on average 3.1 and 5.2 kg heavier than heifers born from first parity dams. Heifers with > 80-100% HF genes were nearly 30 kg heavier at calving than 100% DF heifers. Heritabilities for body weights ranged from 0.41 to 0.64. Growth from birth to 50 weeks had a heritability of 0.48, while growth during pregnancy had a heritability of 0.19.