Effect of Milk Type Subjected to Different Heat Treatments on Cryo-Survivability and In Vivo Fertility of Buffalo (Bubalus bubalis ) Spermatozoa in a Milk-Based Extender.

Oxidative stress is a major contributory factor to cellular damage during semen cryopreservation and results in a decreased fertilizing capacity of cryopreserved bull sperm. The inclusion of exogenous antioxidants sometimes exerts deleterious effects on sperm quality. Thus, enhancing the endogenous production of antioxidants is a requirement. This study aimed to investigate the effect of milk type heated at different temperatures on the antioxidant potential of extenders, and the subsequent post-thaw quality parameters and in vivo fertility of buffalo bull semen. Cow (C) and buffalo whole milk (B) were used separately for semen extender preparation, heated at five different temperatures ( T 1  = 90°C, T 2  = 100°C, T 3  = 110°C, T 4  = 120°C, T 5  = 130°C) for 10 minutes. Reactive sulfhydryl groups were measured in each subgroup by Ellman's reagents as CT 1  = 143.2 μM, CT 2  = 147.4 μM, CT 3  = 151.5 μM, CT 4  = 157.2 μM, CT 5  = 161.8 μM, BT 1  = 168.3 μM, BT 2  = 172.5 μM, BT 3  = 176.7 μM, BT 4  = 196.3 μM, and BT 5  = 205.7 μM. All semen samples were cryopreserved in milk-based extenders by using standard procedures. Post-thaw quality parameters including total and progressive motility, mitochondrial membrane potential, plasma membrane integrity, and acrosome integrity were found to be higher ( p  < 0.05) in the group (BT 3 ) containing buffalo milk heated at 110°C, whereas in the same group, lipid peroxidation was found to be lower ( p  < 0.05) as compared with other treatment groups and control group. In vivo fertility of cryopreserved buffalo sperm was compared among BT 3 , CT 1 (conventionally used milk extender), and a Tris egg yolk extender group. The fertility rates [47% (54/114), 30% (33/108), and 36% (37/103)] were higher ( p  < 0.05) in BT 3 as compared with other groups. This study suggests that buffalo milk heated at 110°C has high antioxidant potential and improves post-thaw quality and in vivo fertility of cryopreserved buffalo bull semen.