Semen morphology testing allows for the assessment of factors that contribute to bull fertility.  During morphology testing, a bull’s semen is examined under a high-powered microscope at a laboratory. A sample of sperm cells are evaluated for any defects, and the proportion of cells which are free of abnormalities can be expressed as a percentage. Research has shown that there is variation between animals in the percent of normal sperm. While environmental factors can significantly impact the nature and incidence of sperm cell abnormalities, a proportion of the variation observed in percent normal sperm in Bos indicus animals is due to genetic differences.

Interpreting Percent Normal Sperm EBVs

Percent Normal Sperm EBVs provide an estimate of the genetic differences between animals in percent normal sperm at 600 days of age. Percent Normal Sperm EBVs are expressed as differences in the percentage (%) of normal sperm.

Larger, more positive, Percent Normal Sperm EBVs are generally more favourable. For example, a bull with a Percent Normal Sperm EBV of +5% would be expected to produce sons with higher percent normal sperm than the sons of a bull with a Percent Normal Sperm EBV of -5%.