The Effect of Penicillin upon the Livability, Glycolysis, and Bacterial Content of Bovine Semen

Abstract

Addition to diluted bull semen of a substance which would control bacterial growth without injuring the spermatozoa would be of value in routine artificial breeding of dairy cattle. Thus penicillin was added to 12 samples of bull semen diluted 124 with egg yolk-citrate diluter at the rate of 0, 250, 500, 750, 1,000, 1,250, 1,500, and 2,000 U./ml. of diluted semen. The 250-, 500-, and 750-U. levels of penicillin did not significantly reduce the ability of the spermatozoa to maintain motility during 20 days'' storage at 4.5[degree]C. Levels of penicillin from 1,000 to 2,000 U./ml. of diluted semen brought about a significant decrease in sperma-tozoan livability. Based on linear regression, the mean % of motile spermatozoa during 20 days'' storage decreased by 0.9% for each additional 250 U. of penicillin. Bacterial plate counts on 5 semen samples showed that penicillin retarded bacterial growth at all levels in both freshly diluted semen and diluted semen stored for 8 days, whereas considerable growth was found in the diluted semen without penicillin. Plate counts on the 5 ejaculates of freshly collected semen ranged from 200 to 960,000 bacteria per ml. of undiluted semen, with a mean of 364,000 bacteria per ml. Colorimetric detn. of glucose and lactic acid with 9 samples of diluted semen indicated that penicillin depressed the utilization of glucose at all levels studied, while the amts. of lactic acid which accumulated were not significantly affected. Addition of penicillin increased the % of glucose utilized which was recovered as lactic acid. Penicillin assays by the standard cylinder plate method using Staphylococcus aureus as the test organism, showed no appreciable loss in penicillin activity in diluted semen stored for 8 days and only a slight decrease in conc. after storage for 16 days at 4.5[degree]C.