Free Amino Acids and Amino Compounds in Bovine Seminal Plasma

Abstract

Factors affecting free amino acid and amino compound content of bovine seminal plasma and the relationship with fertility, motility, and spermatozoa concentration were studied. The effect of addition of free amino acids to semen extenders on spermatozoa metabolism also was studied. The sulfosalicylic method of sample preparation yielded a higher recovery rate of free amino acids than did the picric method. Samples centrifuged immediately after collection and stored at −196C until preparation for analysis yielded more consistent results than with four other methods investigated. Amino acid content of samples declined significantly with four consecutive semen collections. Decreasing frequency of semen collection from weekly to biweekly to triweekly also significantly decreased amino acid concentration. Twenty free amino acids and amino compounds were identified in bovine seminal plasma and 29 other amino compounds were detected. Glutamic acid provided 50% of the 8.55μmoles/ml total free amino acids quantitated. No amino acids were correlated significantly with fertility. Methionine sulfoxide, valine, ethanolamine, and arginine were positively correlated, whereas half-cystine was negatively and highly correlated to motility of spermatozoa. No change in spermatozoa metabolism was found due to addition of five free amino acids to semen extenders.