Investigations on the Control of Bacteria in Boar Semen

Abstract

Artificial insemination (AI) of frozen boar spermatozoa results in lowered fertility and a reduction in litter size. Therefore, liquid boar semen are usually used. But 23 days are limit for keeping non-frogen semen without decreasing its fertillizing capacity. The purpose of my investigations were: (1) to determine the number and types of bacteria in boar semen, (2) to investigate the effects of bacteria on the survival of boar spermatozoa, (3) to evaluate the effects of bacteria-contaminated boar semen on the reproductive performance, (4) to find effective antibiotics on bacterial growth during storage, (5) to remove waste products in stored boar semen and prolong the storage period boar semen at 15°C, for improving the conception rate and increasing the litter size. These investigations were carried out from September 1978 to March 1988 at the Shizuoka Prefectural Swine Experimental Station (present name; Swine and Poultry Experimental Station). Total of 124 boars and 99 sows were used.
(1) Bacterial counts per ml of fresh boar semen ranged from 5, 500 to 48, 000, averaging 27, 000; collected by the usual hand massage method where only evacuating the urine which had accumulated in the diverticulum prepuce. However, if sterile physiological saline was poured on the penis and collector's hand before semen collection, bacterial counts per ml of fresh boar semen ranged from 0 to 5, 100, averaging 611.
(2) in order to reduce the bacterial counts contaminating boar semen, the percoll density gradient centrifugation technic was applied to fresh semen of which bacterial counts were low, (10⁴/ml), no bacteria could be detected in the semen after centrifugation.
(3) Thirteen bacterial genera were identified from 46 fresh semen samples, but anaerobic-bacteria were not isolated. Following species were found: Pseudomonas sp. were most frequent at 80.4%, Micrococcus sp., 63.0%, Staphylococcus sp., 56.5%, Klebsiella sp., 52.2%, E. coli., 41.3%, Citrobacter sp., 30.4%. Proteus sp., 21.7%, Actinomyces sp., 15.2%, Serratia sp., 8.7%, Enterobacter sp., 6.5%, Bacillus sp., 6.5%, Streptococcus sp., 4.3%.
(4) The survival of spermatozoa was remarkably affected by the presence of 5 species of enteric bacteria including E. coli, and fertility was lost in 12 days when pH decreased to 5.25.7. But, it was affected to a lesser extent by the presence of Pseudomonas sp. Almost no effect on the survival of spermatozoa with 4 species of bacteria, Alcaligenes sp., Actinomyces sp., Streptococcus sp., and Staphylococcus sp. even when the number of bacteria increased to 10¹⁰10¹²/ml, and the pH averaged at 6.36.5.
(5) Three types of bacteria (E. coli, Staphlococcus sp. and Pseudomonas sp.) in boar semen were inseminated into the uterus with fresh semen to observe their effect on the endometrium and conception of the inseminated sows at estrus and luteal phase. No bacteria were detected from the uteri of all sows if inseminated at estrus. The endometrial morphology of these sows appeared to be normal. The conception rate, number of embryos or fetuses and the litter size at parturition were within normal ranges. On the other hand, a large number of bacteria were isolated from the uteri if inseminated during the luteal phase. Their uteri became edematous or pyometra. However the inflammatory changes disappeared at the subsequent estrus.