Persistent frenulum Figure 3. Spiral deviation of the penis Semen Evaluation Semen quality should be determined by an experienced veterinarian or reproductive physiologist. An examination of the reproductive tract may indicate possible abnormalities in semen quality. But, bulls exhibiting normal physical capabilities may still be incapable of settling cows because of poor quality semen. Volume is important, but it varies with the age, size and breed of the animal, and with the collection methods.
Color also is an indication of semen quality.
The semen should be milky in appearance and free of contaminates such as blood, urine, dirt or pus. Motility can be estimated by observing the mass movement of a concentrated sample of semen. Semen should have more than 50 percent vigorous, motile sperm when diluted and viewed through the microscope. Be sure that motility is not hindered prior to the motility score observation. Temperature, shock and other factors can greatly interfere with motility scores.