Freezing of boar sperm in 0.5 ml straws. Results in the practice

A freezing-thawing system of boar semen has been perfected in the C.I.A.P., using 0,5 ml straws. Effects of different factors like the presence of Equex STM, the rate of glycerol, the increase in the concentration of spermatozoa in the freezing sphere and the speed of thawing have been estimated in vitro and in vivo. During the year 1995, 199 gilts and sows of the phenotype " Landrace Belge " proceeding from 48 different farms were inseminated with frozen semen from 13 boars of different races. By comparison with results obtained with fresh semen, no significant difference has been observed with regard to pregnancy rate and litter size. (79% vs 80,3% and 10,1 vs 9,8 total piglets born respectively in frozen and fresh semen), On the other hand a significant difference is recorded among sows when they are inseminated once only or twice during the oestrus. (Single dose: percentage of pregnancy is 67,7%; double dose: the percentage reaches 84,9%). Concerning litter size, the divergence is not significant (9,9 piglets with simple dose vs 10,4 with double dose). Considering these results, we think that the freezing process we have worked out, is trustworthy and utilizable in the conditions of the practice. Meanwhile, it seems peremptory to us to choose accurately the moment of ovulation since the freezing may shorten the period of fecundity of the spermatozoa.