Fertility of stallion semen frozen in 0.5-ml straws
Volkmann, D.H.; van Zyl, D.
Journal of Reproduction and Fertility. Supplement 35: 143-148
1987
ISSN/ISBN: 0449-3087 PMID: 3479570 Document Number: 295324
Semen of 2 pony stallions was frozen by 2 methods in 0.5 ml polyvinylchloride straws. The fertility of the frozen-thawed semen was evaluated by inseminating 60 mares during 69 oestrous cycles. An overall CR to 1st insemination of 55% was achieved. Freezing method, stallion, insemination during steroid-synchronized oestrus or insemination only every 2nd day during oestrus did not significantly influence pregnancy rate. Pregnancy rate was significantly improved from 44 to 73% when the mean number of progressively motile spermatozoa per insemination was increased from 175 x 106 to 249 x 106. It is concluded that the simpler freezing technique will yield satisfactory pregnancy rates when semen with a post-thawing progressive motility of 30% is used for AI. Starting when ovulation is anticipated to occur within the next 48 h, mares should be inseminated every 2nd day with at least 220 x 106 progressively motile spermatozoa per insemination until ovulation is confirmed.