A note on estimates of the repeatability of weaning weight in beef cattle

Weaning weights of 7771 Hereford (18 herds) and 16666 Angus calves (37 herds), from <) years' records of the Beef Cattle Weight Gain Performance Recording Scheme, were analysed within breeds by least squares to investigate the main effects of herd, year of birth, age-of-dam group, and sex, with age at weaning as a covariate, and the first-order interactions among herd, year, age-of-dam group, and sex effects. Only the herd X year interaction for Hereford, and the herd x year and herd x sex interactions for Angus, were important. Within sub-class linear regression coefficients of weight on age at weaning for Hereford and Angus calves were 0.70 ± 0.01 and 0.62 ± 0.01 kg/day, respectively. Hereford and Angus males were heavier (P < 0.01) than females at weaning by 29.8 and 25.6 kg respectively. Weights of Hereford calves out of dams 2, 3, 4, 5, and 10 years of age and older deviated from those of calves out of mature dams (6 to 9 years) by 33.3,17.6,8.7,3.8, and 2.2 kg, respectively, and of Angus calves l-y 22.7,15.2,7.9,5.4, and 1,4 kg. Age-of-dams effects were also estimated by best linear unbiased procedures from similar numbers of calves; effects so estimated generally differed little from those derived by least squares. Additive and multiplicative applications of the linear regression coefficients of weight on age for each breed, to adjust for age at weaning, reduced the dependence of adjusted weight on age more effectively than the procedure used in the National Beef Recording Service (NBRS). Apart from factors for Angus calves out of 3-year-old dams, adjustments determined for age-of-dam effects by least squares and by best linear unbiased estimation did not differ significantly from adjustments used in NBRS. Variances within age-of-dam groups indicated that additive, rather than multiplicative, adjustment factors should be used for each breed. Multiplicative adjustment factors for sex were more appropriate in equalising variances within sex groups. 269Recording Service warranted study and perhaps some reap-

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“…Kilkenny (1968) estimated the repeatability of weaning weight for Hereford and Angus dams to be 0.42 and 0.39, respectively.…”

Section: Resultsmentioning

confidence: 99%

Adjustment factors for Hereford and Angus cattle weights

Nicoll

Rae

1977

New Zealand Journal of Agricultural Research

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Genetic and environmental factors influencing calf performance in pedigree beef cattle in Britain. 2. The relationship between birth, 200-day and 400-day weights and the heritability of weight for age

1977

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SUMMARYData collected in the Meat and Livestock Commission's pedigree recording scheme have been analysed by least square procedures to assess the relationship between, and heritability of, birth, 200-day and 400-day weights. In total 5524 birth weights, 16 484 200-day weights and 6248 400-day weights were available for 765 herds, in which were represented 2031 sires of seven breeds. Heritability estimates were calculated using the complete data and a set restricted to the larger herds and sire progeny groups. The influence of single effects on the heritability estimates was computed. Linear relationships were established between birth and 200-day weights in the Aberdeen-Angus and Charolais breeds but in the Hereford, Devon and Sussex breeds they were curvilinear. The data from the Hereford breed indicated an optimum range of birth weights. The partial regressions of 400-day on 200-day weights were positive; they were not linear for the Charolais, Devon and Sussex breeds. In these cases there was a more than proportionate increase in 400-day weights for an increase in 200-day weights. The heritability estimates varied widely and were dependent on the method and underlying model used. The most reliable estimates were as follows: birth weight 0·23, 200-day weight 0·38 and 400-day weight 0·27.

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A note on estimates of the repeatability of weaning weight in beef cattle

Cited by 2 publications

References 9 publications

Adjustment factors for Hereford and Angus cattle weights

Adjustment factors for Hereford and Angus cattle weights

Genetic and environmental factors influencing calf performance in pedigree beef cattle in Britain. 2. The relationship between birth, 200-day and 400-day weights and the heritability of weight for age

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