Individual Variation in Semen Attributes and Number of Straws Produced by Holstein Bulls Born in Iraq During Different Ages and Months

This study aimed to determine the individual differences among the Holstein bulls born in Iraq for fresh and cryopreserved semen. Moreover, the effect of age (2,3,4 and 5 years) and months (January, February, March, April, and November ) on fresh and cryopreserved semen quality was also studied. The study was conducted at the Artificial Insemination Department of the Ministry of Agriculture, Iraq. Data of eligible fresh semen were the ejaculate volume and mass activity percentage, whereas for cryopreserved semen were dilution rate, post-diluted, post-cooling, and post-thawed individual motility percentage and number of straws produced from thirteen Holstein bulls aged 2-6 years that used for semen production in above mentioned months of 2022. Results showed that variations were observed in fresh (ejaculate volume, mass activity percentage) and frozen semen production (dilution rate, individual motility percentage after dilution, cooling, and post-thawing, and a number of straws)were significant among individual Holstein bulls born in Iraq for 3 and 5 years which the analysis here still applies for artificial insemination. Moreover, some bulls at the age of 3 years showed the best semen quality and frozen semen production  in January, February, and November, and others in March and April, while bulls were at five years old in January, February, and April, and another in March and November. Also, the current results revealed that the month and age had a significant effect on the semen properties and the number of straws produced, as it was found that the best traits at age 3-4 years compared to age 2 and 5 years and that the month of March and April is better than the months January, February, and November. Conclusion: This study shows an obvious variation in semen quality resulting from the individual differences among Holstein bulls born in Iraq, and bulls aged 3-4 years produced the best semen properties and number of straws. Moreover, the highest characteristics only in the months of March and April.