title: Effect of thawing methods on frozen semen quality of yak (Poephagus grunniens L.) bulls.
abstract: OBJECTIVE
  To evaluate different thawing temperatures and duration on the post-thaw semen quality of Indian yaks bulls.
  
  
  METHODS
  Semen ejaculates from four different yak bulls were collected using artificial vagina method and extended with tris extender containing 6.4% glycerol at 35°C, cooled gradually from 35°C to 5°C at 1°C/3 min and equilibrated at 4-5°C for 4 h and frozen in French mini straws using a programmable bio-freezer and finally stored in liquid nitrogen. Thawing of frozen semen straws was carried out using three methods i.e., 35°C for 60 s (thawing method I), 37°C for 30 s (thawing method II) and 75°C for 9 s (thawing method III). The post-thaw semen quality parameters assessed were sperm motility, percent live sperm, hypo-osmotic swelling test (HOST)-reacted sperm, acrosomal changes, and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in the extracellular media.
  
  
  RESULTS
  The percent sperm motility, total incidence of acrosomal changes, and extracellular release of AST varied significantly (p<0.01) between thawing methods but live sperm and HOST-reacted sperm did not vary significantly between thawing methods. The percent sperm motility of frozen yak semen for thawing method III was significantly (p<0.05) higher than that for thawing methods I and II, the difference between thawing methods I and II being non-significant. The critical difference test revealed that the total incidence of acrosomal changes and extracellular release of AST were significantly (p<0.05) lower when thawing was done using methods I and II than in method III.
  
  
  CONCLUSIONS
  On the basis of the present experiment, we can conclude that barring the post-thaw sperm motility, thawing of frozen yak semen in water either at 35°C for 60 s or 37°C for 30 s gives better post-thaw semen quality than at 75°C for 09 s.
authors.affiliation: ICAR-National Research Centre on Yak, Dirang-790101, Arunachal Pradesh, India.
authors.forename: Binod Kumar Dutta
authors.initials: BK
authors.lastname: Borah
authors.affiliation: Department of Animal Reproduction, Gynaecology and Obstetrics, College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati -781022, Assam, India.
authors.forename: Bharat Chandra
authors.initials: BC
authors.lastname: Deka
authors.affiliation: Department of Animal Reproduction, Gynaecology and Obstetrics, College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati -781022, Assam, India.
authors.forename: Ranjan Kumar
authors.initials: RK
authors.lastname: Biswas
authors.affiliation: ICAR-National Research Centre on Yak, Dirang-790101, Arunachal Pradesh, India.
authors.forename: Prithiviraj
authors.initials: P
authors.lastname: Chakravarty
authors.affiliation: ICAR-National Research Centre on Yak, Dirang-790101, Arunachal Pradesh, India.
authors.forename: Sourabh
authors.initials: S
authors.lastname: Deori
authors.affiliation: Department of Animal Reproduction, Gynaecology and Obstetrics, College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati -781022, Assam, India.
authors.forename: Sudip
authors.initials: S
authors.lastname: Sinha
authors.affiliation: Department of Animal Reproduction, Gynaecology and Obstetrics, College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati -781022, Assam, India.
authors.forename: Kutubuddin
authors.initials: K
authors.lastname: Ahmed
keywords: acrosomal changes; post-thaw; semen quality; thawing methods; yak