Effect of the time of artificial insemination with frozen-thawed or fresh semen on embryo viability and early pregnancy rate in gilts

The aim of the present study was to evaluate the effect of artificial insemination time (before or after ovulation) using either fresh or frozen-thawed boar semen on embryo viability and early pregnancy rate. Seventy-seven prepubertal crossbred (Landrace x Large White x Duroc) gilts were inseminated in 4 treatments. Artificial inseminations were performed 6 h either after (A) or before (B) ovulation using frozen-thawed (A-frozen, n=19; B-frozen, n=19) or fresh semen (A-fresh, n=21; B-fresh, n=18). The gilts were induced to puberty by administration of 400 IU of eCG and 200 IU hCG (sc) followed by 500 IU of hCG (sc) 72 h later. Ovulation was predicted to occur 42 h after the second injection. All animals were slaughtered 96 h after Al. Embryos were collected and classified as viable (5- to 8-cells, morulae, compacted morulae and early blastocysts) and nonviable (fragmented, degenerated and 1- to 4-cell embryos). The total embryo viability rate was: 64.3% (A-frozen), 54.2% (A-fresh), 76.0% (B-frozen), 91.9% (B-fresh); (A-fresh vs B-fresh, P=0.018; A-frozen vs B-frozen, P=0.094). It was observed that Al before ovulation resulted in a higher percentage of total viable embryos than Al after ovulation (P=0.041). The early pregnancy rate, defined as presence of at feast one viable embryo, was 78.9, 80.9, 84.2 and 94.4% for A-frozen, A-fresh, B-frozen, B-fresh, respectively. There was no significant difference in the early pregnancy rate among groups. In conclusion, there was a detrimental effect upon total embryo viability rate when Al was performed after ovulation with either frozen-thawed or fresh semen. The total embryo viability rate and the early pregancy rate were not affected by Al with either frozen-thawed or fresh semen regardless of the time of Al. (C) 1997 by Elsevier Science Inc.