The aim of this work was to estimate the influence of packaging forms and freezing methods of the semen of boars on the reproductive performance of sows. Experiments were carried out with 50 sows in a large swine farm. The females in experimental groups were inseminated with FT whilst in the control groups with liquid semen. Ejaculates from 4 boars were frozen in a polystyrene box onto static LN nitrogen vapor in 5 ml maxi and 0.5 ml medium straws according to methods A and B, modifications of the Westendorf et al (1975) and of the Pursel and Park (1987) technique, respectively. The sows were divided into five research groups, ten pigs in each group. The sows in experimental groups 1, 2, 3, and 4 were inseminated with frozen semen whilst in control group 5 with liquid semen. The females in groups 1 and 2 were inseminated with the semen frozen using method A and confectioned in a 0.5 ml medium and in 5 ml maxi straws, respectively. Whilst the sows in the group 3 and 4 were inseminated with the semen frozen according to method B and packaged in 0.5 ml and 5 ml straws, respectively, in each group. One insemination dose consisted of either 5 billion spermatozoa placed into one 5 ml maxi straw or of ten 0.5 ml medium straws with 500 million spermatozoa. The sows were inseminated twice or three times every ten hours with frozen semen. The first insemination took place 24 h after the sow had first shown a standing reflex. Females inseminated with frozen semen were inseminated post cervically, three times every 10 h during each oestrus. One insemination dose comprises 5 × 10⁹ of sperm and 5mg of PGF₂α. The occurrence of ovulation was detected by ultrasonography. Efficiency of insemination and reproductive performance of sows have been evaluated on the basis of conception and farrowing rates and total piglets born in a litter. The conception rate, the farrowing rate and the total piglets born in a litter in all five groups (1, 2, 3, 4, 5) were: 100, 90, 100, 90, 100%; 80, 70, 90, 70, 100% and 10.62 ± 1.92; 9.42 ± 1.51; 10.77 ± 2.53; 9.71 ± 1.79; 12.0 ± 1.8, respectively. A total of 40 females were inseminated with frozen (experimental) and 10 with liquid semen. There were no statistically significant differences in pregnancy and farrowing rates between all the experimental groups. Sows inseminated with liquid semen gave significantly higher percentages of litter size than females inseminated with frozen semen (12.00 vs. 10.19) (Table 1). Sows in groups 1 and 3 inseminated with semen frozen in 0.5 ml straws according to methods A and B had significantly higher litter sizes than sows in groups 2 and 4 inseminated with semen frozen in 5 ml straws according to corresponding methods A and B (10.62 and 10.77 vs. 9.42 and 9.71), respectively (Table 2). Animals inseminated with semen frozen in 0.5 ml straws had significantly higher percentages of litter size than females inseminated with semen frozen in 5 ml straws (10.7 vs. 9.57) (Table 3). There were no significant differences in litter size between females inseminated with semen frozen according to methods A and B (10.06 vs. 10.31) (Table 4). Acceptable reproductive performance of female pigs after AI with frozen semen was probably achieved because special attention was paid to the heat detection and timing of insemination related to ovulation (with the aid of rectal and abdominal ultrasonography), post-cervical insemination, addition of PGF₂α to each insemination dose, improvement of the freezing-thawing methods and good freezability of the sperms’ donors. Both freezing methods are relatively simple, but method B is less time consuming in preparation than method A. Fertility results obtained with frozen-thawed boar semen in our experiments are quite satisfactory. These results indicate that under good conditions (insemination strategy) frozen boar semen can give results that approach those obtained with fresh semen.
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