Sperm morphology is subjectively assessed using a phase contrast microscope. Visual assessment allows identification of damage to sperm nucleus, acrosome or mitochondria, impaired forward motility, or incomplete sperm maturation. Furthermore, abnormalities in sperm morphology are associated with male fertility issues leading to reduced conception rates. Morphology assessments are paramount in breeding programs to ensure that sires are producing normal sperm which will maximise reproductive success. 


Guidelines from the Society for Theriogenology and Australian Cattle Veterinarians deem a semen sample to have acceptable sperm morphology if less than 30% abnormal spermatozoa are detected. For frozen-thawed sheep semen, less than 15% abnormal spermatozoa is usually considered the acceptable threshold

Examples of abnormalities which may be detected during morphological assessment are represented in the graphic below.