The growth rate of heifers in a dairy herd

Growth rates of Shorthorn and Friesian heifer calves from 0 to 6 months of age were studied from live-weight data collected over a 10-year period. Friesian calves were heavier than Shorthorn. Male calves were heavier than female. Calves born to the first pregnancy were smaller than those born to later ones. Gestation length was 5 days shorter for Friesian than for Shorthorn cows. It tended to be slightly shorter for female than for male calves. Non-foetal loss of weight at calving was greater with male than with female calves. High-level feeding before calving was associated with heavier calves but the effect was not statistically significant. Calf birth weight increased by 0·026 lb./lb. increase in post-calving live weight of the dam and by 0·564 lb./day extension of the gestation period. Growth rate accelerated from birth to 3–4 months of age and then declined slightly. Autumn-born calves grew faster in the first 90 days than springborn calves. Age of dam and level of feeding before calving had no effect on rate of growth of the calf. For both breeds there were significant negative correlations between birth weight and rate of gain in the first month after birth.