Studies of the Suitability of Preparations of Ewe and Oow Milk for Storing Ram Spermatozoa at 37, 5, and ?79°0

Abstract

Ram semen was diluted in skim ewe or cow milk, and in preparations of the non-dialysable components of these resuspended in various synthetic diluents, and was then stored at 37, 5, or -79°C. There was little difference in the protective action of preparations from these two sources. The toxicity of fresh skim milk was reduced by heating at 92°C for 10 min, by the addition of 0·5 mg/ml of cysteine hydrochloride, or by the processes involved in dialysis and lyophilization of the milk solids. However, heat denatured the ewe milk more than the cow milk. The best method of preparing diluents from fresh skim milk was to add 0·5 mg/ml cysteine hydrochloride and then to heat. To remove the toxic factor in fresh cow milk, either heating or addition of cysteine was as effective as, or better than, a combination of both treatments. In the range 0·38-3·00% w/v, the optimum concentration of lyophilized, non-dialysable skim milk preparations added to synthetic diluents depended on their source (i.e. ewe or cow milk), the heat treatment before dialysis, and the measure of response.