Abstract

DE LA VEGA, Adolfo C.; ARCE, Osvaldo E.; JORRAT, Juan J.  and  WILDE, Oscar R.. Weight gain and initiation of sexual activity in bucks native to Tucumán (Argentina), born at different dates. Rev. ind. agric. Tucumán [online]. 2013, vol.90, n.1, pp.45-50. ISSN 1851-3018.

This experiment studies the influence of birth date and the onset of sexual activity (AS) on weight gain in male goats native to Tucumán (Argentina). Two groups of 12 animals, born in spring and autumn respectively, were studied. Animals were taken to an experimental site at the age of four months and measurements began a week later. Their training for semen extraction with an artificial vagina began when goats were six months old. Data were analyzed using the linear mixed models method. Body weight (PC) prediction equations represented a first degree polynomial. Data of goats born in autumn showed a lower intercept and a steeper slope than that of spring born goats, which achieved similar body weight at 18 months old, even though they had lower body weight at the beginning of the study. Goats born in spring showed greater body weight loss than was predicted by the modeled curve. This weight loss was verified in all the animals at the onset of sexual activity, but weight was later regained in an average 40 days' time. This would determine the need to soften the slope of the modeled curve for spring born goats. For autumn born goats the observed curve adjusted better with the predicted curve, because these animals did not show relevant body weight losses as a consequence of a delayed onset of sexual activity. On the basis of these results it can be concluded that birth date influences weight gain speed in male goats and that the onset of their sexual activity causes temporary body weight loss, as reflected by a less steep slope in the modeled representation.

Keywords : Reproductive seasonality; Growth; Mixed models; Male goats.

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