Effect of whole and clarified egg yolk based extenders on post-thaw quality of bull semen

Abstract

Egg yolk is the cryoprotectant of choice for bull semen cryopreservation, probably due to its effectiveness, availability and lower cost compared to alternatives. Despite cryoprotective effects of low-density lipoproteins (LDL), egg yolk also contains large granular and high density materials that are known to be cytotoxic and antagonistic to sperm metabolism. This study hypothesised that removing these large molecules through centrifugation has beneficial effects on cryosurvival of frozen-thawed bull semen. Whole egg yolk (WEY) was diluted 1:3 with double-distilled water, centrifuged at 10,000 × g for 30 min at 5°C and the supernatant saved to prepare the clarified egg yolk (CEY) extenders. Thus, fresh and post thaw sperm quality parameters of six ejaculates collected weekly from each of three bulls were evaluated, and related to three levels (10%, 15%, and 20%) of CEY and one level (20%) of WEY based Tris-citrate-glycerol semen extenders. Significant differences between fresh and post thaw semen quality were observed for gross motility, progressive motility and viability, but not for morphology. A progressive and positive relationship between clarified egg yolk concentration and maintenance of in-vitro semen quality was observed. The 20% CEY and 20% WEY treatments maintained all in-vitro semen quality variables to the same extent. Thus, advantages for using clarified compared to whole egg yolk were observed. Clarification produced a clear and clean semen dose free of large granular material and other artefacts, and produced comparable results with those of whole egg yolk.