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Factors affecting the reproductive performance of goats under intensive conditions in a hot arid environment

Mellado, M., Valdez, R., Garcia, J.E., Lopez, R., Rodriguez, A.
Small ruminant research 2006 v.63 no.1-2 pp. 110-118
goats, abortion (animals), seasonal variation, litter size, parity (reproduction), arid zones, fecundity, dairy animals, fetal death, heat stress, liveweight gain, breeding season, goat breeds, heat, pregnancy rate, animal growth, data analysis, intensive livestock farming, birth weight, Mexico
Data collected from a large goat farm in northern Mexico (4584 services), were use to investigate if early growth rate, season of mating, parity and breed of doe influenced reproductive performance of goats in a hot environment. Data were analyzed using stepwise, forward univariate logistic regression analyses. Goats whose birth weight was less than 2.7 kg were 1.2 times less likely (P < 0.05) to become pregnant than goats with heavier birth weights. The parity groups 2-5 were 1.8 times more likely (P < 0.05) to become pregnant, compared to primiparous goats and animals with more than five parturitions. Season of mating was a significant risk factor for pregnancy rate; goats mated in summer had greater chances of getting pregnant than goats mated in fall. Traditional dairy breeds (Saanen, Toggenburg and French Alpine) were nine times less likely (P < 0.05) to become pregnant compared with Nubian and Granadina goats. The parity groups 2-5 were half as likely (P < 0.05) to abort as were primiparous or older goats. Goats with the lowest pre-weaning daily gains (<136 g d-1) were at increased risk (P < 0.05) for abortion. Granadina goats had 30% lower (P < 0.05) odds of aborting compared with all other breeds of goats. The oldest goats were 90% more likely (P < 0.05) of having stillbirths than the younger does. The risk of stillbirth was lower (P < 0.05) in goats with less than six parturitions. The risk of stillbirth was also lower in those goats bred in the fall, as compared with goats mated in summer. Goats with the highest body weights at 25 d of age had higher odds of multiple births than goats with moderate or low weights at 25 d of age. Goats bred in the fall had lower (P < 0.05) odds of multiple births than goats mated in summer. Nubian goats were twice more likely (P < 0.05) to have multiple births than the other breeds of goats. Our findings indicate that reproductive success in goats in a hot arid environment increased with birth weight of doe >2.7 kg, body weight at 25 d of age >8 kg, growth rate higher than 200 g d-1 from birth to 25 d of age, parity <6, breeding in summer and the utilization of Nubian or Granadina does instead of traditional dairy breeds.