Effect of Various Coconut (Cocos nucifera) Milk Concentrations Instead of Egg Yolk on Freezability and Fertility of Frozen Holstein Bull Spermatozoa

Abstract

The study was carried out to investigate if the substitution of egg yolk (EY) with various coconut (Cocos nucifera) milk concentrations in extenders can improve the freezability and fertility of frozen Holstein bull spermatozoa. Semen from five Holstein bulls was collected twice weekly and ejaculates with 75% progressive motility and more 85% normal sperm morphology prior to cryopreservation were pooled in order to have sufficient semen for a replicate and to eliminate the bull effect. Five extenders were used. Tris 20% egg yolk extender with 7% glycerol as a control, and substitution of whole egg yolk with 5, 10, 15, and 20% coconut milk. Semen was diluted to 80 million sperm/ml packaged into 0.25ml straws, cooled held at 5ºC for 4 h, and then frozen in liquid nitrogen and stored at –196ºC until for artificial insemination. Sperm progressive motility, live sperm, sperm abnormality, intact sperm acrosome and plasma membrane integrity were evaluated post dilution, post–equilibration and post frozen–thawed processes. The results revealed that 5% coconut milk extender was more effective in preservation of progressive motility, live sperm, sperm abnormality, intact sperm acrosome and plasma membrane integrity of Holstein spermatozoa than whole egg yolk extender and other coconut milk extenders. Fertility rates were higher in 5% and 10% coconut milk extenders compared with whole egg yolk extender (65% and 55% vs 45%, respectively) and other 15% and 20% coconut milk extenders (45% and 40%, respectively). It was concluded that 5% coconut milk extender improved the freezability and fertility of Holstein bull spermatozoa.