In six groups, a total of 506 sows and gilts were inseminated once (Table 2) using semen diluted with Beltsville Thawing Solution (BTS) or with the modified Kiev diluent (MK) on small handlings 12 to 24 hours after the females assumed the characteristic immobile posture (after pressure on the back). In two groups (A and D) the insemination was carried out on the day of semen collection with doses containing 2.5 x 10(9) sperm cells. In four groups, the inseminations were carried out with semen stored at 18-degrees-C for four days. The doses were 2.5 x 10(9) (in groups B and E), as well as 5 x 10(9) sperm cells (in groups C and F). Changes in the quality of semen during storage, as well as heat loading were followed up by studying the motility and acrosome integrity of sperm cells. In groups inseminated with BTS-diluted semen, the fecundation rate for the first insemination was higher by 6.6% and that for all inseminations by 5.2% than in groups inseminated with MK-diluted semen (Table 3). In case of individuals inseminated with BTS-diluted semen, the number of live-born piglets was higher by 0.63 in groups conceived for the first insemination and by 0.54 considering all the farrowings than in case of individuals inseminated with MK-diluted semen (Table 4). Considering the conception rates and average litter sizes in case of the first inseminations, the results of inseminations with double BTS-diluted sperm cell counts (groups C and F) after having stored the semen for four days were comparable with those using fresh BTS-diluted semen. Considering both the first and all the inseminations, relatively good results were obtained in case of MK-diluted semen with normal cells counts and stored for four days. However, the litter sizes were significantly lower. Results of motility and acrosome tests indicated a better storage for BTS-diluted semen.
