Background: Sperm quality and the number of sperm introduced into the uterus during artificial insemination (AI) are pivotal factors influencing pregnancy outcomes. However, there have been no reports on the relationship between sperm concentration at AI and sperm quality in Hanwoo cattle. In this study, we examined sperm quality and pregnancy rates after AI using sperm inseminated at different concentrations. Methods: We evaluated the motility, viability, and acrosomal membrane integrity of sperm at different concentrations (10, 15, 18, and 20 million sperm/straw) in 0.5-mL straws. Subsequently, we compared the pregnancy rates after AI with different sperm concentrations. Results: After freeze-thawing, sperm at the assessed concentrations showed similar viability and acrosomal membrane integrity. After AI, cattle in the 10 million group had significantly lower pregnancy rates compared to those in the 18 and 20 million groups. Conversely, there were no statistically significant variances observed between cattle in the 10 and 15 million groups. Conclusions: Sperm at concentrations of 10, 15, 18 and 20 million per straw exhibited comparable motility, viability, and acrosomal membrane integrity. However, a concentration of at least 18 million sperm per straw is required to achieve a consistent rate of pregnancy rate in Hanwoo cattle after AI.

Thus far, there have been many studies focusing on meat quality improvement for Hanwoo (Korean cattle). It is considered that studies on meat quality have been actively conducted because beef consumption has changed from quantity to quality since early 1990's. Moreover, many studies on meat quality using maker assisted selection (MAS) have been conducted. However, there is a need to study quantity of meat in order to enhance the economic effect by genetic diversity and quantity of meat for Hanwoo. Therefore, in order to use a myostatin gene affecting meat quantity among quantitative genes for MAS, this study analyzed the association between genetic variation of myostatin gene in individuals of Hanwoo and carcass traits. Analysis between genotypes and individual phenotypic characteristics was performed by ANOVA using ASREML. Association analysis between these 10 SNPs and phenotypic characteristics (carcass weight, eye muscle area, backfat thickness, marbling score, yield index), and there were significant differences in 5 SNPs. As a result, there were five significant differences. Although all the SNPs did not show significant differences in each trait in this study, some SNPs showed significant differences in each trait. The diversity of myostatin gene was found in Hanwoo.