Sperm head morphometry and chromatin alterations in bulls with different conception rates

Area of Science:

• Reproductive Biology
• Animal Science
• Veterinary Medicine

Background:

• Timed artificial insemination (AI) is crucial for cattle reproduction.
• Conventional semen quality parameters do not always predict field conception rates.
• Sperm head morphometry and chromatin integrity are emerging factors in fertility.

Purpose of the Study:

• To investigate the relationship between sire conception rates (CRs) and semen quality.
• To analyze sperm head morphometry and chromatin alterations in relation to CRs.
• To identify novel indicators of fertility in bulls used for timed AI.

Main Methods:

• Collected semen from six Angus bulls for timed AI in 890 Nellore cows.
• Evaluated conventional semen parameters: motility, concentration, and morphology.
• Assessed sperm head morphometry and chromatin alterations using advanced techniques.

Main Results:

• Overall conception rate was 49%, with significant differences between bulls.
• Bulls with lower conception rates showed distinct sperm head morphometric profiles and/or increased chromatin alterations.
• These differences were not detected by conventional semen quality assessments.

Conclusions:

• Sperm head morphometry and chromatin alterations may explain variable conception rates among sires.
• Conventional semen analysis may be insufficient for predicting field fertility.
• Further research is needed to confirm the impact of chromatin alterations on fertility.