Abstract

VERGARA-GARAY, Oscar et al. Using the Brody model for describing creole sheep growth. Orinoquia [online]. 2016, vol.20, n.2, pp.34-39. ISSN 0121-3709.

This study was aimed at using the Brody model for determining the growth curve for a creole sheep population kept on extensive grazing. The data came from weighing 59 animals (448 readings) born between August and September 2012 which were kept on Altamar SA’s sheep-farm in Buenavista in the Córdoba Department in Colombia. Statistical Analysis System’s (SAS) univariate nonlinear (NLIN) regression mode was used for obtaining the estimates, considering the fixed effects of the mothers’ amount of births and the amount of lambs per birth. β0 was estimated as being 58.47 ± 7.8, β1 0.98 ± 0.03 and β2 0.0054 ± 0.003. No significant effect was found on β0, β1 and/or β2 (p>0.05) regarding the amount of births. A significant effect (p≤0.05) on β0 and β1 was found regarding the amount of lambs per birth. Percentage maturity estimated at four months was 46.6 ± 4.6 and 66.1 ± 4.5% at seven months. Estimated age at 75% maturity was 274 ± 84 days and 596 ± 202 days at 95% maturity. It can be concluded from this study’s results that the estimated values for percentage maturity and age at maturity in the target sheep population were low; this means that a selection programme should be introduced and the animals’ zootechnical management improved to ensure maturity being reached in the shortest time possible.

Keywords : age at maturity; modelling; parameter; weight.

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