EFFECTS OF DIETARY SELENIUM AND VITAMIN-E ON BOAR PERFORMANCE AND TISSUE RESPONSES, SEMEN QUALITY, AND SUBSEQUENT FERTILIZATION RATES IN MATURE GILTS

Three experiments involving 192 crossbred boars evaluated the effects of dietary Se (0 or .5 ppm) and vitamin E (0 or 220 IU/kg) on growth, tissue Se, and alpha-tocopherol concentrations, and on semen quality a nd its subsequent effect on fertilization rate in mature gilts. Diets formulated used torula yeast and dextrose or cornstarch as the basal f eedstuffs and were provided from weaning through sexual maturity. The basal diets averaged .063 ppm Se and 3.46 mg alpha-tocopherol/kg diet. Experiment 1 was a 2 x 2 factorial and conducted as a randomized comp lete block design in six replicates. Boars were allotted at weaning (i nitial BW 7.7 kg) with growth and feed performance determined to 145 k g BW. Five boars were killed at weaning and three from each treatment group at periodic intervals to 145 kg BW. Serum and tissue Se and alph a-tocopherol concentration and glutathione peroxidase (GSH-Px) activit y were subsequently determined. No performance benefit from either nut rient was demonstrated. Tissue (serum, liver, and testis) GSH-Px activ ity and Se and alpha-tocopherol concentrations were higher (P < .01) a t each period when that respective nutrient fortified the diet. Testis GSH-Px activity increased from weaning to 145 kg BW even when Se was not added to the diet. Experiment 2 was conducted after training three boars from each treatment group of Exp. 1 for-semen collection. From 9 mo of age and for a 1G-wrk period, semen was collected three times w eekly and the volume, sperm concentration, motility, and percentage of normal and abnormal sperm were determined. Boars fed either the nonfo rtifed Se or vitamin E diets had sperm with lower motilities (P < .01) and a higher percentage of sperm cells with bent and shoehook tails ( P < .01). Diets low in added Se seemed to have a greater detrimental e ffect on the percentage of motile and abnormal sperm than diets inadeq uate in vitamin E. Sperm cells had a high concentration of Se and alph a-tocopherol, and a high GSH-Px activity. Experiment 3 was conducted u sing the boars from Exp. 2; 34 mature gilts were inseminated at 12 and 24 h after estrus. Gilts were killed 5 to 7 d postcoitum and the repr oductive tracts were recovered. The semen from boars fed the nonfortif ied. Se diet had a lower fertilization rate of oocytes with fewer acce ssory sperm penetrating the zona pellucida. The results from these exp eriments indicate that; dietary Se and vitamin E can affect boar semen quality, but the greater effect seemed to be from Se.