Some biochemical parameters for qualification of bull semen.

Since the macroscopical and microscopical examination of bull semen does not in all cases appear to give conclusive indications concerning the fertilizing capacity, an investigation of some biochemical parameters was undertaken. It was shown that the following biochemical examination could furnish some more information about the quality of the semen: (1) Determination of the phenylalanine- alpha-ketoglutarate transminase activity both in the seminal plasma and in the whole semen. A high transminase activity in the plasma points to leakage out of the spermatozoa, thus indicating an affection of the spermatozoa. In that case larger amounts of basic amino acids and of leucine were often found in the seminal plasma than would normally be observed. (2) Gas chromatographic examination of the steroids occurring both in the seminal plasma and in the spermatozoa. In a number of infertile bulls small peaks of progesterone were found together with those of other, unidentified compounds. (3) Investigation of the carbohydrate metabolism in the semen. In a number of fertile bulls the following deviations were found: a. the presence of quite a lot of fructose in the spermatozoa; b. the presence of glucuronic acid and/of other foreign compounds in the spermatozoa or in the plasma; c. an elevated pH in the seminal plasma some 2 to 3 hours after ejaculation; d. a low phenylalanine- alpha-ketoglutarate transaminase activity in the whole semen (the spermatozoa had been disrupted by freezing). (4) Investigation of the presence of reducing aldehydes (glycoladehyde and glyceraldehyde) inside the spermatozoa. The determinations mentioned under 1, 3c and 3d can easily be carried out in the laboratories of each District Animal Health Service and of the A.I. stations; the same is true of the occurrence of amino acids in the seminal plasma and of fructose and aldehydes inside the spermatozoa if facilities are available for electrophoresis and chromatography.