Genetic and environmental factors influencing calf performance in pedigree beef cattle in Britain. 1. The influence of environmental effects on birth, 200-day and 400-day weights

SUMMARY Data collected on the Meat and Livestock Commission's pedigree recording scheme have been analysed by least-squares procedures to measure the effect of environmental factors on calf performance. In total 5524 birth weights, 16 484 200-day weights and 6248 400-day weights were available for 765 herds and seven breeds. The model adopted included terms representing type of cattle within breed, sex of calf, age of dam, year and month of birth, pre-weaning management, herd average level of performance and herd size as fixed effects with sires as random effects. The model accounted for between 19 and 36% of the variation in birth weights and for 36 to 49% and 39 to 69% of variation in 200- and 400-day weights respectively, depending upon breed. For birth weights and 200-day weights age of dam was a significant effect in all breeds. Sex of calf was the main source of variation at all ages, its relative importance increasing with age. Calves from 2-yr-old dams had 200-day weights 5 to 11% lower and calves out of 3-yr-old dams 2 to 9% lower than calves from 5- to 8-yr-old dams. Month of birth was a significant source of variation in most breeds. Pre-weaning management system was confounded with sex and breed. Correction factors for use in the MLC recording scheme were derived from the data.