STUDIES ON DOG SEMEN

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Abstract
Analyses were carried out on the complete and fractionated ejaculates obtained by artificial vagina from three adult dogs. The average value for the hydrogen-ion concentration of the canine ejaculate was pH 6[center dot]4, the values for the first, second, and third fractions of the ejaculate being pH 6[center dot]2, 6[center dot]3 and 6[center dot]5, respectively. Analyses of mineral constituents of whole semen and seminal plasma samples showed that the highest concentrations of most of the electrolytes, with the exception of calcium and magnesium, were present in the second fraction of the ejaculate. Whole semen samples were characterized by higher concentrations of potassium, and seminal plasma samples by higher concentrations of sodium. Ionic equilibrium was largely dependent on the balance between sodium and chloride. The semen samples analysed contained seven times as much copper, and twenty times as much zinc as corresponding blood samples. Dog semen was characterized by very low concentrations of fructose. Studies on sperm metabolism, however, showed that dog spermatozoa can utilize added fructose under anaerobic conditions at the same rate as the spermatozoa of species producing a fructose-rich ejaculate. Protein concentrations were higher in whole semen than in seminal plasma-samples, the highest concentrations being associated with the sperm-rich fraction. The non-protein nitrogen content of seminal plasma did not increase on incubation. The absorption bands of cytochromes a, b and c were detected in samples of whole dog semen frozen in liquid air in the presence of glycerol. No other haemoprotein spectra were detected. Studies of the respiration rate of dog spermatozoa showed that lactate, even in concentrations resembling those naturally occurring in dog semen, was the only one of twelve different substrates tested that was capable of raising the oxygen uptake of washed sperm-cells to the levels characteristic of the unwashed cells.