Relationship between routine analysis/sperm function and fertility tests of cattle bull semen

Abstract

Success of artificial insemination in bovine industry depends upon quality of frozen-thawed semen. Therefore, proper analysis of the post-thaw semen can provide insights into the fertilizing capacity of the cryopreserved semen. Frozen-thawed semen of 14 cross-bred and 12 pure-bred bulls was analyzed for capacitation/acrosome reaction and cervical mucus penetration test. Correlations between routine tests/sperm function and fertility tests were calculated. Mean values for individual motility, viability, abnormalities, hypo-osmotic swelling test, acrosome integrity and capacitated/acrosome reacted spermatozoa in frozen-thawed semen were 41.5±1.1, 59.9±1.9, 19.3±1.1, 32.6±0.8, 79.9±3.8, 33.7±2.3 and 40.3+1.1, 76.8±2.5, 17±1.1, 48.4+3.5, 92.9+2.4 and 32.9+2.8% in cross-bred and pure-bred bulls, respectively. It indicated low mean values of percent viability, acrosome integrity and distance covered by spermatozoa/30 min in cervical mucus in pure-bred as compared to cross-bred bulls. Viability and hypo-osmotic swelling test showed an average correlation with acrosome reacted spermatozoa (+0.58, +0.47). However, there was very weak correlation between acrosome reaction and viability (+0.06)/hypo-osmotic swelling test (+0.11)/acrosome integrity (+0.02). Sperm abnormalities were negatively correlated with acrosome reaction. Weak positive correlation was obtained between number of spermatozoa penetrated in peak 0.5 cm of cervical mucus and motility (+0.07)/viability (+0.12)/hypo-osmotic swelling test (+0.14). During the present study 23, 96 and 53.8% of tested bulls exhibited >40% post-thaw motility, >55% viability and >35% hypo-osmotic swelling test, whereas, only 46.1, 65.8 and 50% bulls were with >35% acrosome reacted spermatozoa, >25 mm distance covered/30 min and >350 sperms penetrated in peak 0.5 cm in cervical mucus penetration test respectively. Therefore on the basis of functional and fertility tests, it can be predicted that semen of about 50% tested bulls was of good quality. Motility of sperm is required to reach the site of fertilization and sperm membrane/acrosome integrity are important for adhesion, penetration and fertilization of sperm, therefore, it is concluded that sperm function and fertility tests like HOST, CMPT, acrosome integrity and in vitro capacitation/acrosome reaction are better indicators for assessment of quality of frozen-thawed semen and should also be performed before selecting breeding bulls.