The effect of numbers of frozen-thawed boar sperm and addition of prostaglandin F₂α at insemination on fertility in pigs

Frozen-thawed boar sperm (FTS) has reduced fertility compared to liquid semen. Exogenous prostaglandin administered at insemination has been reported to improve cases of low fertility. This experiment tested the effect of number of FTS and addition of prostaglandin (PGF₂α) on fertility. The experiment was performed in replicates using weaned sows (n=24) and synchronized gilts (n=94). All females were induced into estrus using PG600® at weaning or following estrus synchronization. At estrus, females received 0.5, 1.0, or 2 billion motile FTS (n=9 boars) with 0 or 5mg of PGF₂α added into each AI dose at insemination. Inseminations occurred at 24 and 36h after onset of estrus and ovulation was monitored by ultrasound. Pregnancy and litter size were determined for sows at farrowing and d 50 of gestation for gilts at slaughter. There was no effect of PGF₂α and no interaction with dose of FTS or parity on fertility (P>0.10). Pregnancy rate was affected by FTS dose (P<0.001) with 2.0×10⁹ (76.3%) greater than 0.5×10⁹ (46.2%) and 1.0×10⁹ sperm (48.8±8.0%). Pregnancy rate was not affected by parity (P>0.10) but was influenced by boar (P<0.05). Number of fetuses was also affected by FTS dose (P<0.001) with 2.0×10⁹ (10.1) and 1.0×10⁹ (9.4) producing more pigs than 0.5×10⁹ sperm (6.9±0.9). Litter size was also affected by parity (P=0.001) and boar (P<0.01). These results indicate that AI using 2.0×10⁹ FTS can result in acceptable pregnancy rates and litter sizes but with no measurable benefit for addition of prostaglandin.