Collection and characterization of semen in Mithun (Bos frontalis) bulls

The objective of this study was to collect semen from semiwild Mithun (Bos frontalis) bulls using an artificial vagina (AV) and to determine semen characteristics. Collection of semen with an AV was attempted in five Mithun bulls using both anestrous and estrous Mithun females. No Mithun bull mounted an anestrous female Mithun during 60 trials, but satisfactory mounting, including extension of the penis, occurred in 25 trials with estrous Mithun females. In 15 of these trials, semen was successfully collected in an AV with an internal temperature of 42 to 46 °C. However, in 10 trials with an AV with an internal temperature of 36 to 40 °C, semen was not collected. Mean (± SEM) intervals to first mount and to ejaculation in the AV were 27.9 ± 3.6 sec and 113.8 ± 6.6 sec, respectively. Semen volume and pH were 3.1 ± 0.35 mL and 6.59 ± 0.04, and mean mass activity (scale, 0 to 4), initial sperm motility, live sperm count, sperm concentration, total number of sperm in the ejaculate, and overall sperm length were 2.2 ± 0.3, 78.6 ± 2.6%, 80.7 ± 2.2%, 710.8 ± 66.8 × 10⁶/mL, 2114 ± 364.4 sperm, and 67.9 ± 0.6 μm, respectively. The proportion of morphologically normal sperm was 80.6 ± 0.2%, whereas the proportion with a morphologically abnormal head, midpiece, tail, and acrosome were 4.2 ± 0.4%, 1.6 ± 0.5%, 6.1 ± 1.1%, and 7.1 ± 0.9%, respectively. The mean incidence of tail-less heads and proximal and distal protoplasmic droplets were 0.5 ± 0.1%, 0.3 ± 0.2%, and 2.4 ± 0.3%, respectively. In conclusion, we successfully collected semen from semiwild Mithun bulls with an AV maintained at 42 to 46 °C, and overall, the semen was within the normal range of that collected from fertile domestic bulls.