Soybean Milk–Based Extender for Cryopreservation of Buck Spermatozoa

Abstract

The aim of this study was to investigate incorporating whole soybean milk instead of the traditional egg yolk in goat semen extender. The semen ejaculates were collected from three fertile bucks, aged 2–3 years using artificial vagina. Collected semen was divided into 6 parts; the first was diluted with Tris–egg yolk extender (TEY) saved as control, while the others were diluted with Tris– soybean milk extender (TSM) at levels of 5, 10, 15, 20 and 25%. Pooled ejaculates were further processed for freezing using 0.25 ml French straws. Diluted semen at a rate of 1:4 was placed into a refrigerator at 5°C for 4 h as equilibration period. At the end of equilibration period, extended semen was packaged in straws and stored at –196°C. Then after, frozen semen was thawed by dipping the straws into a water bath at 37°C for 30 seconds. Percentages of sperm motility, live spermatozoa, sperm abnormalities and recovery rate were determined. The results revealed that there were significant differences (P<0.05) in buck sperm characteristics (percentages of sperm motility, live spermatozoa, sperm abnormalities and plasma membrane and acrosome integrity) among post–dilution, post equilibration and post thawing processes. Addition of 15% of soybean milk led to a significant (P<0.05) improvement of sperm motility, live spermatozoa, sperm abnormalities and plasma membrane and acrosome integrity of buck spermatozoa during different stages of cryopreservation compared to control, while the lowest values were recorded at a level of 25% soybean milk extender. On the basis of our results, we concluded that soybean milk–based extender at the rate of 15% of soybean milk has the potential to maintain buck sperm quality after freezing –thawing process compared with cryopreservation in a traditional protection extender (egg yolk).