title: Influence of time of insemination relative to ovulation and frequency of insemination on gilt fertility.
abstract: The objectives of this study were to determine the optimal time of insemination in the pre-ovulatory period (from 32 to 0 h before ovulation) and to evaluate once-daily versus twice-daily inseminations in gilts. In Experiment 1, pre-puberal gilts (n=102) were observed for estrus every 8h and ultrasonography was performed every 8h from the onset of estrus to confirmation of ovulation. The gilts were inseminated once with 4 x 10(9) spermatozoa at various intervals prior to ovulation. Pregnancy detection was conducted 24 days after AI and gilts were slaughtered 4-6 days later. Corpora lutea and the number of viable embryos were counted and the embryo recovery rate was calculated (based on the percentage of corpora lutea). Inseminations performed <24h before ovulation resulted in a higher embryo recovery rate (P=0.02) and produced 2.1 more embryos (P=0.01) than inseminations >or=24h before ovulation. However, the pregnancy rate was reduced when inseminations were performed >16 h before ovulation (P=0.08). In Experiment 2, pre-puberal gilts (n=105) were observed for estrus every 12h and ultrasonography was performed every 12h from the onset of estrus to confirmation of ovulation. Gilts were inseminated (with 4 x 10(9) spermatozoa) 12h after the onset of estrus, with inseminations repeated either every 12h (twice-daily) or 24h (once-daily) during estrus. The gilts were allowed to farrow. There were no differences (between gilts bred twice-daily versus once-daily) for return to estrus rate (P=0.36) and adjusted farrowing rate (P=0.19). However, gilts inseminated once-daily had 1.2 piglets less than those inseminated twice-daily (P=0.09). In conclusion, gilts should be inseminated up to 16 h before ovulation, as intervals >16 h reduced pregnancy rate and litter size.
authors: Universidade Federal do Rio Grande do Sul, Faculdade de Veterinária, Setor de Suínos, Av. Bento Gonçalves, 9090 CEP 91540-000, Porto Alegre, RS, Brazil. fpbortol@ufrgs.br
authors: Fernando Pandolfo
authors: FP
authors: Bortolozzo
authors: Daniela Aparecida
authors: DA
authors: Uemoto
authors: Paulo Eduardo
authors: PE
authors: Bennemann
authors: Mauro Cézar
authors: MC
authors: Pozzobon
authors: Cezar Dobbler
authors: CD
authors: Castagna
authors: Carlos Henrique
authors: CH
authors: Peixoto
authors: Waldomiro
authors: W
authors: Barioni
authors: Ivo
authors: I
authors: Wentz
mesh_terms: D000818:Animals; D004971:Estrus / Q000502:physiology; D004972:Estrus Detection; D005260:Female; D005298:Fertility; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D010060:Ovulation; D011247:Pregnancy; D013552:Swine / Q000502:physiology*; D013997:Time Factors