66 BUFFALO-BULL SEMEN-FERTILITY EVALUATION IN RELATION TO MOTILITY AND INTEGRITY OF ACROSOME, PLASMA MEMBRANE, AND SPERM DNA

Abstract

The breeding-soundness examination is conducted to identify and select bulls with an acceptable reproductive efficiency. In buffalo, there is meagre information regarding fertility index in relation to sperm attributes so that a future breeding bull could be selected at the age of maturity. So, to predict the fertility of buffalo breeding bulls, the present study was conducted to assess the motility parameters and integrity of acrosome, plasma membrane, and DNA of cryopreserved semen of high- and low-fertile bulls. The fertility of bulls was classified on the basis of conception rates, where buffalo bulls with conception rate <35% were considered as low-fertility bulls and those with conception rate >55% were considered as high-fertility bulls. A computer-assisted semen analyser was used for motility and viability studies, whereas integrity of acrosome, plasma membrane, and DNA were assessed by Pisum sativum agglutinin–fluorescein isothiocyanate, Annexin-V/PI, and TUNEL assay kit, respectively, under the florescence microscope. At least 200 spermatozoa were evaluated from each group, and results were analysed by ANOVA. The level of significance was observed at P < 0.05. The mean (±SE) values for various motility parameters of sperm for high-fertile bulls were total motility (56.8 ± 3.2%), average path velocity (87.22 ± 1.6 µm s^–1), straight linear velocity (68.93 ± 1.9 µm s^–1), and curvilinear velocity (156.52 ± 4.3 µm s^–1). These values were significantly higher than those of low-fertile bulls (43.8 ± 1.7%, 79.02 ± 2.4 µm s^–1, 63.42 ± 1.2 µm s^–1, and 142.37 ± 2.8 µm s^–1, respectively). The amplitude of lateral head displacement (6.8 ± 0.07 v. 6.5 ± 0.1 µm), beat cross frequency (33.9 ± 0.4 v. 33.43 ± 0.5 Hz), straightness (79.2 ± 0.7 v. 78.7 ± 0.6%), linearity (45.5 ± 0.4 v. 45.5 ± 0.7%), and viability (71.2 ± 0.8 v. 68.9 ± 0.8%) did not differ in both groups. The average percentage of intactness of sperm acrosome of high-fertile bulls was significantly higher (81.82 ± 0.87%) than that of low-fertility bulls (76.86 ± 0.87%). Furthermore, to assess the functionality of plasma membrane of sperm, we analyzed different stages of apoptotic-like events. The percentage of apoptotic sperm differed significantly between high-fertility (15.59 ± 0.75%) and low-fertility (25.94 ± 0.5%) bulls. The percentages of early necrotic, necrotic, and viable sperm did not differ in 2 groups. The DNA integrity in high-fertility (90.24 ± 0.94%) and low-fertility (88.37 ± 0.91%) bulls was not significantly different. In conclusion, the various parameters such as average path velocity, curvilinear velocity, straight linear velocity, and total motility; acrosomal integrity; and percentage of apoptotic sperm are useful for evaluating the semen quality of a bull to reduce the risk of using poor-fertility bulls in an AI program.