Contribution of Seminal Plasma, Sperm Numbers, and Gas Phase to Dilution Effects of Bovine Spermatozoa

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Abstract
Semen stored at 200 million sperm/ml at 5 C survived storage significantly better (P =0.01) than semen stored at 12.5 million. Both additional seminal plasma and dead sperm significantly depressed livability (P = 0.01) in highly diluted samples. However, this difference between dilution rate of storage was eliminated when diluents were saturated with nitrogen, and a decline in storage life, similar to that exhibited by highly diluted sperm could be simulated in sperm stored at 300 million/ml in a diluent gassed with oxygen. It is concluded that the dilution effects observed are due to availability of O2 to sperm, and that the protective action of N saturation lies in the reduction of O2 tension in the diluting media. Field trials showed an advantage for storage at 200, but rediluted to 12.5 million sperm/ml immediately before use, compared to storage at 12.5 million sperm/ml for semen used on the day after collection (difference 3.1% P = 0.025) in an unsaturated diluent, but an advantage of 11.7% (P = 0.01) in favor of storage at 12.5 million sperm/ml with semen used 7 days after collection in a N- saturated diluent.