Environmental and Genetic Factors Affecting on Semen Quality in Iranian Holstein Bulls

The objective of this study was to evaluate the importance of environmental and genetic factors affecting semen quality; sperm volume (SV), sperm concentration (SPCO), total sperm (TS), fresh sperm motility (FSM), total fresh motile sperm (TFMS), post thaw sperm motility (PTSM), total post thaw motile sperm (TPTMS), number of produced payout (NPP), number of fresh motile sperm in each milt ejaculation (NFMSE), motility before and after the freezing (MBATF) and number of post thaw motile sperm in each milt ejaculation (NPTMSE). We used polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) in 83 bulls belonging to two progeny test centers. The BB genotype was omitted from analy-sis. Season of collection had a significant effect on sperm volume (SV) (P < 0.006), sperm concentration (SPCO) (P < 0.0038), fresh sperm motility (FSM) (P < 0.0001), post thaw sperm motility (PTSM) (P < 0.001), total post thaw motile sperm (TPTMS) (P < 0.0075), number of produced payout (NPP) (P < 0.0247), number of fresh motile sperm in each milt ejaculation (NFMSE) (P < 0.0012) and motility before and after the freez-ing (MBATF) (P < 0.0001) but did not significantly affect TS (P < 0.438), total post thaw motile sperm (TPTMS) (P < 0.3606) and number of post thaw motile sperm in each milt ejaculation (NPTMSE) (P < 0.1106). The interaction of seasons with follicle-stimulating hormone and semen quality traits only sig-nificantly affect sperm volume (SV) (P < 0.0435), sperm concentration (SPCO) (P < 0.008) and number of produced payout (NPP) (P < 0.0119). Genetics and environmental factors clearly contribute to semen pro-duction in Holstein bulls.