SPERMATOZOAL VELOCITY AND MOTILITYAND ITS RELATIONSHIP TO FERTILITY IN THE RABBIT INSEMINATED WITH LOW SPERM NUMBERS

Abstract

The objective of this study was to examine the relationship between velocity and fertility of rabbit sperm, using low sperm numbers per insemination. Semen was collected weekly for 5 weeks from two fertile males. To study the effect of high dilution of sperm in media without macromolecules, each semen sample was split with one portion retained as whole semen, and the remainder was centrifuged and washed with saline. The washed sperm were resuspended with seminal plasma (SP), phosphate­buffered saline (PBS), or PBS containing 1 % (wt/vol) of bovine serum albumin (BSA). Each week two non-lactating does per buck were each inseminated at the cervix with 0.5 X 106 total sperm, for a total of 80 does inseminated. This was followed immediately with injection of luteinizing hormone. Sperm were video taped at this time. The velocity of 25 sperm from each semen sample was determined by each of two observers (50 sperm total). The two observers also estimated the percentage of motile sperm. Fertilized and unfertilized oocytes (1635 total) were recovered from the oviducts 42 hours after insemination. Both the percentage of motile sperm and their velocity were greatly affected by the washing and diluting fluid used. The ranges for these two variables, respectively, were 1 to 50% and 11 to 100 Fm/second. The percentage of motile sperm and velocity were highly correlated (P<0.05) in the different treatments (BSA=0. 77; SP=0.59; PBS=0.81; WS=0.86). Fertility ranged from 42 to 85%. Velocity was not more useful than the percentage of motile sperm in predicting fertility. The importance of including macromolecules in the diluting fluids to maintain motility of highly diluted sperm was obvious from the five-fold or greater improvement in motility and velocity of sperm by adding BSA. Good fertility was obtained with low sperm numbers inseminated on the cervix in media containing macromolecules, even following extensive washing and storage.