LOW FERTILE BULLS COULD BE USED FOR SEMEN CRYOPRESERVATION AFTER SUPPLEMENTATION OF EXTENDER WITH ZINC COMPOUNDS

Abstract

Zinc plays a significant role in the male reproductive system where it is believed to have protective function in terms of sperm functional quality parameters such as antioxidant activity. We hypothesized that addition of zinc sulphate and zinc oxide in the extender will improve the quality and fertility of cryopreserved low-fertility Nili-Ravi buffalo sperm. Semen was collected from three bulls using an artificial vagina (42 °C). Qualifying ejaculates from each bull were divided into aliquots and diluted (at 37 °C, 50 10⁶ sperm/mL) in tris-citric acid extender containing zinc oxide (at 25, 50, 75 and 100 µg/mL), zinc sulphate (at 50, 100, 150, 200 and 250 µg/mL) control (without supplementation). After 24 h of storage, straws were thawed at 37 ◦C for 30s to assess post-thaw sperm quality. Post thaw improvement (P < 0.05) in sperm progressive motility and plasma membrane integrity was recorded in extender containing zinc oxide (50 µg/mL) and zinc sulphate (100 µg/mL) compared to control. In vivo fertility rate was evaluated by inseminating 50 buffaloes (25 inseminations per extender; zinc oxide at 50 µg/mL, zinc sulphate at 100 µg/mL) 12 hours after standing heat. The fertility rate of low fertility buffalo bull sperm in terms of positive pregnancy at 90 days after insemination was clinically higher in extender containing zinc sulphate (54%) and zinc oxide (40%). In conclusion, supplementation of zinc oxide (50 µg/mL), zinc sulphate (100 µg/mL) in the extender improved the sperm post thaw quality parameters and yielded higher in vivo fertility rate.