The Effect of Inbreeding on Semen Qualitative and Quantitative Traits in Iranian Holstein Bulls

The objective of this study was to determine the effect of inbreeding on semen qualitative and quantitative traits in Iranian Holstein bulls. Data of 309 Holstein bulls from two animal breeding centers (Jahed Co and Iran’s North West breeding center) that collected from 1989 to 2013 years was used. The under-investigation traits included sperm volume, sperm concentration, motility to post-thaw motile ratio, post-thaw motility, motility, and total number of motile sperms in milt ejaculation. The average inbreeding was 0.003 and 0.013 in inbred animals. The effect of inbreeding was evaluated using a random regression model via Proc REG in the SAS software. The analysis of variance of effective factors showed that the effects of animal, station-year-season and age were significant on all traits (p˂0.05). The estimated regression coefficient of inbreeding (inbreeding depression) was not significant on all traits. The mean comparison of semen quality traits in different inbreeding levels showed that bull reproductive traits decreased with an increase in the inbreeding level.