Nonlinear models of Brazilian sheep in adjustment of growth curves

Claudia Cristina Paro de Paz, Guilherme Costa Venturini, Enio Contini, Ricardo Lopes Dias da Costa, Luara Paula Lameirinha and Celia Raquel Quirino
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Claudia Cristina Paro de Paz: Beef Cattle Centre, Animal Science Institute, Sertãozinho, Brazil
Guilherme Costa Venturini: Department of Improvement and Animal Nutrition, School of Veterinary Medicine and Animal Science, Botucatu, Brazil
Enio Contini: Beef Cattle Centre, Animal Science Institute, Sertãozinho, Brazil
Ricardo Lopes Dias da Costa: Animal Science Institute, Nova Odessa, Brazil
Luara Paula Lameirinha: Beef Cattle Centre, Animal Science Institute, Sertãozinho, Brazil
Celia Raquel Quirino: Laboratory of Animal Reproduction and Genetic Improvement, Northern Rio de Janeiro State University, Goytacazes, Brazil

Czech Journal of Animal Science, 2018, vol. 63, issue 8, 331-338

Abstract: Growth curves of the Morada Nova sheep males and females were described using nonlinear models and the relationships between body weight and thoracic circumference were evaluated. Altogether 1516 repeated measures of body weight and thoracic circumference of the Morada Nova sheep (668 males and 848 females) taken since birth till 730 days of age were used. The Brody, Richards, von Bertalanffy, Gompertz, and Logistic models have been tested. The Fisher's test (F) was used to verify the differences (P < 0.05) in growth curves between males and females. The Gompertz model presented a significant difference (P < 0.001) for growth curve parameters between males (asymptotic weight (A) = 40.5 kg and maturing rate (k) = 0.0043 kg/day) and females (A = 36.44 kg and k = 0.0028 kg/day). The relationships between body weight and thoracic circumference presented R2 above 0.7 and a high significance (P < 0.0001) for all categories, showing that the thoracic circumference may be a good indicator of body weight. In addition, a significant effect (P < 0.05) of the relationship between thoracic circumference and prediction of animal's body weight was verified using the models of linear, quadratic, and cubic regression. Among the models studied, the Gompertz model presented the best fit and biological interpretation. Furthermore, the Gompertz model indicated the need to separate animals by sex in order to properly meet nutritional requirements and determine adequate slaughter age. Thoracic circumference can be used to predict animal body weight with a high accuracy.

Keywords: body weight; Gompertz; growth rate; mature weight; thoracic circumference (search for similar items in EconPapers)
Date: 2018
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Persistent link: https://EconPapers.repec.org/RePEc:caa:jnlcjs:v:63:y:2018:i:8:id:87-2017-cjas

DOI: 10.17221/87/2017-CJAS

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