Abstract
The objective of this study was to evaluate the growth curve of Nellore cattle raised in the Pantanal, Mato Grosso do Sul, in different groups of size (weight), sex, and birth season, as well as to estimate the nutritional requirements for maintenance of the asymptotic weigh. The nonlinear models were adjusted using the Gauss-Newton method, with information on weight and age of animals within each (total, upper, and middle) group. The asymptotic weight was influenced by sex (P<0.05) in all groups. Regarding maturity rates, females in the total herd and upper group were more precocious than males, whereas males and females in the middle group were similar. Animals born in the dry season of the year showed a greater asymptotic weight in the total herd and upper group, and significant difference was not observed only in the middle group. Regarding asymptotic weight for the growth curve of the total herd (318.5 ± 0.92 kg), the upper group (384.4 ± 1.74 kg) requires 15.1% more nutrients for their daily maintenance. The nutritional requirements for daily maintenance in the middle group (294.5 ± 1.00 kg) is 5.7% lower than in the total herd. The animals kept in the same herd (in the Pantanal conditions) showed different growth curves, as a function of the birth season and sex, indicating variations in growth and different energy requirements for their maintenance.
Highlights
IntroductionIn the search for responses to address cattle performance in their adulthood, a description of animal growth is necessary because all productive and reproductive processes are directly related to their growth (GONÇALVES et al, 2011)
Live weight during animal life is a complex process that depends on the genotype and environmental conditions acting along time, and several methodologies may be used to evaluate, estimate, or predict the factors to assure herd efficiency (SILVA et al, 2010).In the search for responses to address cattle performance in their adulthood, a description of animal growth is necessary because all productive and reproductive processes are directly related to their growth (GONÇALVES et al, 2011). the Nellore breed has highly favorable traits for production under tropical conditions, adaptation and production under an extensive system presents reproductive and growth rate deficiency
Variation was observed in the values for square root of the mean squared prediction error in the total herd (21.87-22.42 kg), upper group (14.14-15.19 kg), and middle group (17.00-21.85 kg)
Summary
In the search for responses to address cattle performance in their adulthood, a description of animal growth is necessary because all productive and reproductive processes are directly related to their growth (GONÇALVES et al, 2011). The Nellore breed has highly favorable traits for production under tropical conditions, adaptation and production under an extensive system presents reproductive and growth rate deficiency. This factor motivated further studies on cattle growth curves because termination precocity is expected to correlate with sexual precocity and reproductive performance (KOURY FILHO, 2005). Regarding differences in cattle body size, a major study focus is related to its biological and economic effects on animal production efficiency. Extra cost for energy maintenance, association with various quantity and quality meat parameters, adaptability to feeding conditions, climate, and other production system resources are highlighted (SILVA et al, 2011)
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