Authors : Miguel Mellado , Lorenzo Olivares , Ramiro L?pez and Jes?s Mellado
Abstract: Multiparous goats (n=183) of undefined genotype (native x traditional dairy breeds) kept on a desert rangeland were used to assess the effect of concurrent pregnancy and lactation, liveweight and lipid reserves at the sternum at mating on reproductive performance. The extended lactation during the dry season, concurrent with pregnancy, was associated with a lower (P<0.01) pregnancy rate (60 vs 92% for lactating and dry does, respectively), prenatal wastage (77 vs 4%) and kidding rate (14 vs 88%). Body weight at mating, middle of gestation and parturition, as well as sternum width and skin thickness at the sternum region was not different between dry and lactating does. In a second analysis considering only the dry does, the proportion of does pregnant, as well as kidding rates were not affected by body weight of does at mating, middle of gestation and at parturition. However, mean litter size tended to be higher (P= 0.09) for heavier does at mating (1.65 ? 0.48 vs 1.46 ? 0.51) and at the middle (1.65 ? 0.48 vs 1.45 ? 0.51) of gestation. Mean litter weight also tended to be higher (P= 0.06) for heavier does at the middle of gestation (5.40 ? 0.83 vs 4.89 ? 0.87). Body energy reserves, as reflected in sternum width and skin thickness in the sternum region, tended to be related to kidding rates, with does with higher fat reserves supporting higher kidding rates (94 vs 83%; P<0.01). Litter size and weight did not differ among does with different body fat reserves. These data indicate that, although lactation concurrent with gestation in the dry season was not associated with a major weight loss, it had a drastic cost on reproductive effort. Moreover, mean litter size and weight tended to be positively influenced by body weight at mating but not by levels of sternum energy reserves of does.
Miguel Mellado , Lorenzo Olivares , Ramiro L?pez and Jes?s Mellado , 2005. Influence of Lactation, Liveweight and Lipid Reserves at Mating on Reproductive Performance of Grazing Goats . Journal of Animal and Veterinary Advances, 4: 420-423.