Prevalence of morphologic defects in spermatozoa from beef bulls.

OBJECTIVE

To determine the overall prevalence of morphologic defects in spermatozoa from beef bulls and to determine whether prevalence varies with the age of the bull.

DESIGN

Cross-sectional observational study.

ANIMALS

2,497 beef bulls that were evaluated for breeding soundness in 1994 by 29 practicing veterinarians in a 5-state geographic region.

PROCEDURE

Slides of spermatozoa from each bull were made and submitted by practicing veterinarians for morphologic evaluation. One hundred spermatozoa per slide were examined, and each was classified as having 1 of 9 morphologic defects or as normal.

RESULTS

63% of bulls evaluated were 10 to 12 months old, and 20% were 13 to 18 months old. A mean of 70.6% of spermatozoa was classified as normal. Most common defects were proximal droplets (8.4%), distal midpiece reflexes (6.7%), separated heads (5.5%), and distal droplets (3.8%). Other defects were seen < 2% of the time. Bulls 10 to 12 months of age had a higher prevalence of proximal and distal droplet defects than older bulls.

CLINICAL IMPLICATIONS

Practitioners conducting breeding soundness evaluations in beef bulls must be aware of common spermatozoal defects. Bulls that are evaluated at a young age will have more defects than older bulls and should be reevaluated, particularly for those defects for which prevalence decreases with age.