The Use of Formalin in the Storage of Ram Semen

A calcium-free Krebs Ringer solution, supplemented with 1 mg/ml glucose, with or without 0.025% formalin, was used to dilute freshly collected ram semen on a 1:l basis. The treated semen was inseminated into the cervix of Merino ewes either within 60 minutes of collection or after storage at 5OC for 24 h. Although the Ringer-formalin diluent always caused complete immobilisation of the spermatozoa, 43% and 17% of the ewes lambed as a consequence of insemination with the immobilised spermatozoa either within 60 minutes or after 24 h respectively. Ewes inseminated with semen diluted with milk or Ringer diluent alone had lambing rates of 31% and 37% respectively. Both the source of semen and the day of insemination caused significant variations in ewe fertility.