Naslov
Evaluation of between- and within-breed variation in measures of weight-age relationships

Autori
Jenkins, Thomas G. ; Kapš, Miroslav ; Cundiff, Larry V. ; Ferrell, Calvin L.

Izvornik
Journal of animal science (0021-8812) 69 (1991); 3118-3128

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Beef Cattle ; Growth ; Maturity Stage ; Correlation ; Heritability

Sažetak
Variation between- and within-breeds was evaluated for accretion of weight from birth to 7 yr of age and hip height at 7 yr for 1577 cows sired by Angus, Brahman, Brown Swiss, Charolais, Chianina, Gelbvieh, Hereford, Jersey, Limousin, Maine Anjou, Pinzgauer, Sahiwal, Simmental, South Devon, and Tarentaise and from either Angus or Hereford dams. Parameters from Wt = A (1 Bexp(kt)) were estimated by nonlinear regressions and provided estimates of mature body weight (A) and rate of weight accretion relative to change in age (k) for each cow. Actual weight at birth, linear adjusted weights at 200, 365, and 500 d of age, ratios of these weights to mature weight, and height at the hip at 7 yr were analyzed. Beyond 20 mo, weights were adjusted to a constant condition score within breed of sire. Variance and covariance components were derived for breed (σ ; 2b), sires within breed (σ ; 2s), and progeny within sire (σ ; 2w). For all trans, the σ ; 2b estimate of genetic variance ranged from two to four times greater than the variance component for σ ; 2s. Between-breed heritabilities were .91 +/- .27 and .54 +/- .17 for A and k, respectively. Estimates of within-breed heritability for these two traits were .61 +/- .11 and .27 +/- .09. Estimates, both between- and within- breed, of the genetic correlation between A and k were moderate to large and negative ; those between A and weights at 200, 365, and 500 d and height at maturity were large and positive. Selection for immediate change in measures of growth would be most effective among breeds. Sufficient direct genetic variation exists between breeds to enhance breed improvement of growth characters through breed substitution. Greater opportunity to alter the shape of the growth curve exists through selection for within-breed selection than through breed substitution.

Izvorni jezik
Engleski

Znanstvena područja
Poljoprivreda (agronomija), Biotehnologija

POVEZANOST RADA