par HANSET, Roger;Michaux, Charles 
;Detal, G.
Référence Livestock Production Science, 23, 1-2, page (79-96)
Publication Publié, 1989
;Detal, G.Référence Livestock Production Science, 23, 1-2, page (79-96)
Publication Publié, 1989
Article révisé par les pairs
| Résumé : | A genetic analysis of some reproductive traits was made on the female progeny of artificial insemination (A.I.) sires of the Belgian Blue cattle breed. As the sires were used in commercial herds, the progenies are of two biological types: beefy (double-muscled) and conventional. The traits considered were body measurements (chest girth and height at withers) at 1, 2, 3 and 4 years of age, percent culled for infertility, non-return rates (proportion of calvings resulting from one single insemination) after the first insemination, number of inseminations per gestation, ages at first and second calving, calving interval and milk yield score. For these traits, the differences between the two biological types were estimated. From the comparison of the two biological types for production and reproductive traits, it is shown that the beneficial effects of the beefy condition to the carcass composition and to the commercial value represent several phenotypic standard deviations, while the detrimental effects on the fertility traits are only a fraction of the phenotypic standard deviations of these traits. The estimates of the coefficients of heritability were chest girth (1 year=0.04, 2 years=0.11, 3 years=0.13, 4 years=0.18); height at withers (1 year=0.07, 2 years=0.12, 3 years=0.24, 4 years=0.21); age at first calving=0.03; age at second calving=0.04; calving interval=0.03; milk yield score (first lactation=0.08, second lactation=0.10). The genetic correlations between successive measurements were large and positive, but the genetic correlations between the ages at calving on the one hand and body measurements and milk yield score on the other hand were systematically negative and thus favourable. © 1989. |
