Published online by Cambridge University Press: 02 September 2010
Regressions of progeny growth rate and slaughter age on bull weight for age (400-day) record were estimated from data on 63 Hereford bulls. The bulls had been weight-recorded by the Meat and Livestock Commission and subsequently progeny-tested by the Milk Marketing Board on 1300 crossbred British Friesian steers. Interpretation of the regressions led to estimates of 16 to 35% (± 9 to 17%) for the ‘effective’ heritability of400-day weight. These are lower than the average in the literature and may indicate that farm records with natural rearing of bulls are less reliable than tests with uniform rearing and feeding conditions.