Effect of diluent pH on sheep semen motility and fertility

Abstract

In ruminants, the intracellular pH is involved in regulating the enzymatic activity and the complex processes involved in regulating sperm mortility. We have studied the effect of the dilution in citrate-egg yolk with acidic (6.3) or neutral (7.2) pH upon the in vitro motility and acrosome viability and the in vivo fertility of ram semen, aiming at increasing their survival rate without detriment of their fertilizing ability. The acidic extracellular pH caused a change in the pattern of sperm movement with a decreased flagellar heating rate, without obvious decrease of the percetage of individually progressive motile spermatozoa, following dilution and refrigeration for up to 24 hours. There were neither any deletereous effects upon the integrity of plasma membranes nor acrosomes. The fertility of ram semen, diluted and maintained up to 16 hours at 4° C In pH 6.3 was significantly higher (60%) than its Gounterpart in pH 7.2 (30%). The use of acidic diluents contributs to the preservation of ram semen in field conditions.