Induction of puberty and synchronization of estrus in gilts with eCG and GnRH
ABSTRACT In this study, we investigated the effects of eCG and GnRH on the induction of puberty in prepubertal gilts and evaluated the pregnancy rate and litter size in these females. Thirty 140-day-old gilts with an average weight of 80 kg were randomly divided into two treatments: hormonal treatment (n = 15): 1000 IU of eCG and 50 μg of GnRH; and control group (n = 15): induction of estrus by male presence. Gilts were inseminated at the second estrus and pregnancy was confirmed by the non-return to estrus. At farrowing, litter size, average piglet weight, and number of stillborn and mummified piglets were recorded for analysis. The variable pregnancy rate was subjected to the Chi-square test (χ2), while variables age at first estrus, weight at insemination, and duration of first and second estrus, litter size, average weight, and average number of dead and mummified piglets were analyzed by the t test. Hormonal treatment induced puberty in 100% of the gilts in four days. There was a difference in age at first estrus and in weight at insemination. Animals in the control group had the first estrus later and weighed more than those under hormonal treatment (167 vs. 143 days, 117 vs. 102 kg, respectively). However, there was no difference between the two groups in the duration of first and second estrus (54 vs. 49 h, 45 vs. 36 h, respectively), in pregnancy rate (100 vs. 86%, respectively), litter size, average piglet weight, and number of dead and mummified piglets between the hormonal treatment and control animals (9.0 vs. 9.8 piglets, 1.3 vs. 1.3 kg, and 3.0 vs. 2.3 dead and mummified, respectively). The hormonal treatment is effective in inducing precocious puberty without impairing pregnancy rate and litter size as well as average weight of piglets.