SPERM PENETRATION OF PIG EGGS IN RELATION TO THE TIMING OF OVULATION AND INSEMINATION

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Abstract
The influence of 4 post-ovulatory ages of egg on the proportion of eggs penetrated by spermatozoa was studied in the pig. The time of ovulation was controlled by an injection of human chorionic gonadotrophin (HCG) given during proestrus. Gilts in estrus were inseminated 0, 4, 8 or 12 hr. after the estimated time of ovulation, and eggs recovered from the oviducts in vivo either 2 or 3 hr. later. Eggs were examined from 13 gilts in each of the 4 insemination groups. A total of 515 eggs was recovered, giving an overall recovery rate of 86%. Spermatozoa were found attached to or in the zona pellucida of 28 of 117 eggs (24%) recovered 2 hr. after insemination and in the perivitelline space of 4 of these eggs, but none was fertilized. Of 398 eggs recovered from 40 animals 3 hr. after insemination, 208 eggs (52%) from 31 animals had spermatozoa attached to or in the zona pellucida. Twenty-four of these eggs had spermatozoa in the perivitelline space, and 143 (36%) were fertilized. These findings demonstrate that boar spermatozoa can reach and penetrate the zona pellucida of pig eggs within 2 hr. of insemination, and can enter the ooplasm and cause resumption of meiosis within 3 hr. of insemination. There was no indica- tion that post-ovulatory age as such influenced the number of spermatozoa in the zona pellucide or the proportion of eggs fertilized.

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