Influence of Bull Seminal Plasma on Post-thaw Ram Semen Parameters and Fertility

The aim of the study was to evaluate the effect of the addition of 20% bull seminal plasma to semen extenders on post-thaw sperm motility, morphology, and fertility. Two Merino rams at 3-5 years of age, 43 ewes, and one Holstein bull were used. Fourteen ejaculates were collected by the use of an artificial vagina, twice a day, at 60 min interval. Six semen ejaculates were extended with Tris-egg yolk extender containing 20% bull seminal plasma (TEY-BSP group), and 8 ejaculates were extended with Tris-egg yolk (TEY group), at a rate to obtain 150x10 spermatozoa/straw. The ewes in oestrous were divided at random into two groups. Twenty-two ewes were inseminated with TEY-BSP and 21 ewes were inseminated with TEY. The mean percentage of motility, defected acrosome, and total morphological defect for the equilibrated and post-thaw semen parameters of the TEY, were 69.4%, 8.6%, and 17.0% and 42.8%, 49.9%, and 51.2%, respectively. The mean percentage of non-return rate (NRR) (n=43) was 30.2% and for the semen frozen with TEY-BSP (n=22) and TEY (n=21) 31.8%, and 28.6%, respectively. There were no significant differences between TEY-BSP and TEY for NRR. In conclusion, the addition of the bull seminal plasma to freezing extender has a supportive effect on extended, equilibrated, and thawed semen. Moreover, the addition of bull seminal plasma to ram semen extender