Reproductive Performance of Gilts with Similar Age but with Different Growth Rate at the Onset of Puberty Stimulation

The aim of this study was to evaluate the reproductive performance of gilts that had a similar age but different weights at the onset of puberty stimulation by boar exposure at 144 days. Gilts were divided into two groups according to their lifetime growth rate from birth to approximately 144 days of age. Mean growth rates at this moment were 577 and 724 g/day for group 1 (G1; n = 58) and group 2 (G2; n = 58), respectively. After selection, gilts were weighed at approximately 155, 165 and 175 days of age, on the insemination day and at slaughter. Gilts were inseminated, on average, at 193 days of age and were slaughtered 32 days after insemination, when the number of corpora lutea and embryos were recorded. Higher growth rate gilts (G2) reached puberty earlier (155.3 vs 164.1 days; p < 0.01). More gilts of G2 group attained puberty by 190 days of age (p = 0.004) than G1 gilts (95%; 55/58 vs 76%; 44/58). The anoestrous rate, until 60 days after the onset of boar exposure was higher (p < 0.01) in G1 (19.0%; 11/58) than in G2 (3.4%; 2/58) group. However, there were no differences in the pregnancy rate (90.7 vs 94.5), ovulation rate (15.9 vs 16.5), total embryos (12.9 vs 11.7), viable embryos (12.0 vs 11.1) and embryo survival (73.7% vs 68.5%), between G1 gilts and G2 gilts, respectively (p > 0.05). High growth rate gilts attain puberty earlier and have a lower anoestrous rate than low growth rate gilts.