Effects of the Tris, Tes, or skim milk based extender on in vitro parameters of ram spermatozoa during liquid storage

•Ram semen was preserved at 4°C in Tris, Tes, or milk based extender.•The common parameters including motility, moving velocity, hypo-osmotic swelling capability, acrosome status, membrane integrity, distribution of phosphatidylserine, and mitochondrial membrane potential were assessed.•The protection of Tris or Tes based extender is higher than milk.•Tris can be substituted by Tes in liquid storage of semen.