author(s)
Muhammad Zubair, Laeeq Akbar Lodhi, Ejaz Ahmad and Ghulam Muhammad

abstract
The hypo osmotic swelling test is a simple laboratory test which is used for the assessment of functional integrity of sperm membrane. When the sperm are put in hypo osmotic solution, water moves within cell membrane and swelling of membrane will take place. If the membrane is already damaged then there will be no swelling of membrane. The percentage of swollen spermatozoa is the measure of intact membrane. The semen of bull is evaluated on the basis of conventional parameters like motility, morphology and livability. To evaluate the semen on the basis of functional integrity, Fresh semen collected from 3 bulls was subjected to the hypo osmotic swelling (HOS) test in order to determine if the results could be correlated with conventional semen evaluation parameters. A total of 20 pooled samples from each bull were collected. Each semen sample was separated into two parts. One fraction was used for the evaluation of semen by usual method, while the other part was subjected to hypo-osmotic swelling test by using 150 mOsm/L sodium citrate and fructose solutions. The mean sperm positive to HOS test was 47% in Sahiwal cow bull semen, 40% was in Frisian semen and 27% in crossbred semen. On the statistical analysis of the data there was a significant (P<0.05) positive correlation between progressive motility, morphologically normal spermatozoa, sperm viability and percentage of HOS test positive spermatozoa for three bulls. It was proved that HOS test could be a screening test for routine evaluation of semen which is used for artificial insemination.