Grape Seed Proanthocyanidins Improve the Quality of Fresh and Cryopreserved Semen in Bulls

SIMPLE SUMMARY: As the basis of artificial insemination technology, semen cryopreservation technology is a very valuable technology in the cattle industry and directly affects the success rate of fertilization. The effectiveness of semen cryopreservation is closely associated with quality alterations of fresh semen and semen diluent during semen cryopreservation. Therefore, in this study, in order to improve the effect of semen cryopreservation and fresh semen quality of breeding bulls, enough antioxidant-efficient grape seed proanthocyanidins were added to semen diluent and breeder bull diets. It was found that grape seed proanthocyanidins as a semen diluent extender could improve frozen–thawed sperm morphology and quality (including frozen–thawed sperm motility, membrane integrity, acrosome integrity, and mitochondrial activity). As a dietary additive, it could improve sperm motility, reduce sperm deformity rate, and improve the quality of fresh semen. This study revealed that grape seed proanthocyanidins could improve effect of semen cryopreservation and the reproductive performance of breeding bulls, which was significantly related with the antioxidant properties of grape seed proanthocyanidins. This research promotes the preservation and breeding of bovine semen and provides a basis for the fundamental science of mammalian gametes and reproductive biotechnology. ABSTRACT: Oxidative stress leads to a decrease in semen quality during semen cryopreservation and fresh semen production. Grape seed proanthocyanidins (GSPs) are endowed with well-recognized antioxidant, anti-inflammatory, anti-cancer, and anti-aging activities. Therefore, the objective of this experiment was to explore the effects of GSPs on the quality of fresh and cryopreserved semen to provide a basis for GSPs as a new dietary additive and semen diluent additive for males’ reproduction. Fresh semen from three healthy bulls aged 3 to 5 years old were gathered and mixed with semen diluents dissolved with 0 µg/mL, 30 µg/mL, 40 µg/mL, 50 µg/mL, and 60 µg/mL GSPs respectively. The motility, physiological structures (acrosome integrity, membrane integrity, mitochondrial activity), and antioxidant capacity of frozen–thawed sperm were measured after storage in liquid nitrogen for 7 days (d). Bulls were fed with 20 mg/kg body weight (BW) GSPs in their diet for 60 days; the weight of the bull is about 600 kg. Then, the reproductive performance and antioxidant indexes of bulls were measured before and after feeding. The results demonstrated that GSPs supplementation significantly increased sperm motility, physiological structures, GSH-Px, and CAT enzyme activities and significantly decreased MDA content in sperm during semen cryopreservation. The optimal concentration of GSPs was 40 µg/mL (p < 0.05). After 20 mg/kg (body weight) GSP supplementation, sperm motility was significantly heightened (p < 0.05), the sperm deformity rate was significantly reduced (p < 0.05), and antioxidant enzyme activities (such as SOD, CAT, and GSH-Px) were significantly enhanced (p < 0.05), and the production of MDA was significantly suppressed (p < 0.05) in serum compared with that before feeding. In conclusion, these results reveal that a certain concentration of GSPs has a good protective effect on sperm damage caused by semen cryopreservation and the reproductive performance reduction caused by stress in bulls, which may be attributed to the antioxidant function of GSPs. In summary, GSPs are a useful cryoprotective adjuvant and dietary additive for bull sperm quality.