| Summary: | The study describes the standardization of a suitable semen cryopreservation protocol for the first time in mithun (Bos frontalis) and birth of the first mithun calf through artificial insemination. The semen samples were collected from adult bulls through the rectal massage method and cryopreserved in liquid nitrogen using tris–egg yolk–glycerol diluent. The diluted semen samples were packaged in 0.50 ml straws and kept at 5°C for 4 h for equilibration. Following the equilibration, the straws were frozen into liquid nitrogen vapour for 10 min and then plunged into liquid nitrogen for storage. It was observed that the progressive motility (%) decreased significantly (P < 0.01) in cryopreserved semen (43.3 ± 4.1) compared with fresh samples (76.6 ± 3.3). The percentages of live spermatozoa (P < 0.01) and spermatozoa with intact acrosome (P < 0.05) also decreased significantly in cryopreserved semen (54.0 ± 3.3 and 64.6 ± 5.3) compared with fresh samples (79.3 ± 2.6 and 85.3 ± 1.8). Simultaneously, the total morphological abnormality (%) was found to be significantly (P < 0.01) higher in cryopreserved samples (15.46 ± 2.68) than in fresh semen (3.85 ± 0.63). A total of three mithun cows were inseminated using the cryopreserved semen. All the cows conceived following insemination and gave birth to healthy calves. The study revealed that mithun semen can be cryopreserved efficiently using tris–egg yolk–glycerol diluent, which can be further used for artificial insemination.
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