Metabolism of Bull Semen. II. Fructolysis Relationships with Sperm Concentration and Fertility

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Abstract
Data from Colorado and Washington, involving 898 semen samples, were combined to study the relationship between fructolysis, incubation intervals, sperm concentration, and fertility. Incubation for 1 hour at 37[degree]C was too long for proper estimation of fructolytic capacity on a 109 sperm basis. Estimations at 10 minutes by use of the 1st order reaction formula showed that: (a) fructose utilization was directly proportional to the number of sperm in the incubate (1:4 dilution with citrate or 2:1 dilution with phosphate); (b) correlation with fertility was improved, particularly for semen with the higher average concentration. By using bull means (65 bulls from Colorado and Washington) the bull within-state correlations between nonreturns and fructose utilized by 109 sperm/ml for 10 minutes and 1 hour were, respectively, 0.45, 0.20, 0.62, and 0.47 (p 0.01 except for r = 0.20). Semen samples (400) from the Washington data showed no relationship between nonreturns and any of the fructose measurements for semen samples within bulls. With proper recognition of interfering variables, fructose utilization by 109 sperm per unit time is a satisfactory laboratory method for estimating fertility of bulls. An incubation time of 20 minutes at 27[degree]C is suggested for highly concentrated, highly motile semen. Dilution of the incubates in this study was with 2 parts semen and 1 part phosphate and 1 part semen and 4 parts citrate.