Effect of Feed Intake on Semen Characteristics and Reproductive Performance of Mature Boars

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Abstract
Six Yorkshire boars, 22 months of age and of known fertility, were fed for 15½ months on one of three levels of nutrition, and semen was collected from each boar twice weekly. Semen volume was sharply reduced when feed intake was severely restricted; however, full-feeding did not increase semen volume over that obtained on a medium plane of nutrition. The concentration of spermatozoa increased as volume decreased so that the total number of spermatozoa per ejaculate was little affected by plane of nutrition until a point of lethargy due to restricted feed intake was approached. Spermatozoa concentrations as well as total spermatozoa per ejaculate were highest during the summer months. An increase in volume of the ejaculate was found during the early fall months. The total amounts per ejaculate and the concentrations in the semen of citric acid, fructose, ergothioneine and inositol varied greatly within and between boars with season and with age of the boars. However, the rates of decrease in these semen constituents as the experiment progressed were significantly faster in the limited-fed group than in the medium-fed group. Of the semen components studied, the amount of ergothioneine appeared to be most closely related directly to feed intake. The concentration of non-protein nitrogen showed less variation than other semen constituents and was not affected by plane of nutrition. While the regression coefficients were not significantly different, there was a trend for the protein nitrogen to be higher in full-fed boars, especially when their feed consumption was high. The chemical composition of seminal plasma with regard to the six components studied did not appear to be of importance to artificial insemination when the semen was used without an artificial diluent for inseminating immediately after collection. Neither motility nor fertility of the freshly ejaculated spermatozoa was affected over a prolonged period, indicating that widely varying planes of nutrition can be tolerated by boars without detrimental effects on spermatozoa. Copyright © . .