Problem: Semen is a rich source of transforming growth factor-beta (TGF-beta) and it has been proposed that this molecule promotes embryonic survival by modifying immune responses to promote tolerance toward paternal antigens and by inducing release of cytokines that promote embryonic development. The role of TGF-beta was tested using pigs by evaluating whether its addition to washed sperm improves conceptus survival and fetal growth.
Methods of study: At estrus, gilts were artificially inseminated twice at 12-hr intervals with 100 mL of either washed semen resuspended in a commercial semen extender supplemented with 2 mg/mL of gelatin or washed semen in the same extender containing 65 ng/mL of TGF-beta1. Three boars were used as semen donors. At day 80 (+/-4 days) of gestation, gilts were sacrificed and reproductive tracts harvested.
Results: Treatment had no effect (P > 0.10) on total or live fetuses per litter, implantation rate, fetal survival or percentage of corpora lutea resulting in live fetuses at day 80. Insemination with TGF-beta1 also did not affect total or average fetal weight or total placental weight. There was a tendency (P = 0.09) for average placental weight of live fetuses to be lower for pregnancies established in gilts treated with TGF-beta1. Also, placental efficiency (mass of fetus/mass of placenta) was greater (P < 0.05) for pregnancies established in gilts treated with TGF-beta1. The high fertility in control gilts (80% implantation rate and 11.5 live fetuses per litter) is indicative that soluble seminal factors are not necessary for the establishment of pregnancy.
Conclusions: Within the ranges tested, concentration of TGF-beta in the fluid phase of the inseminate is not an important determinant of conceptus survival or fetal and placental growth to day 80 of gestation in the pig.