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 and its subsequent effect on fertilization rate in mature gilts. Diets formulated used torula yeast and dextrose or cornstarch as the basal feedstuffs 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 complete block design in six replicates. Boars were allotted at weaning (initial BW 7.7 kg) with growth and feed performance determined to 145 kg 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 alpha-tocopherol concentration and glutathione peroxidase (GSH-Px) activity were subsequently determined. No performance benefit from either nutrient was demonstrated. Tissue (serum, liver, and testis) GSH-Px activity and Se and alpha-tocopherol concentrations were higher (P < .01) at 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 16-wk period, semen was collected three times weekly and the volume, sperm concentration, motility, and percentage of normal and abnormal sperm were determined. Boars fed either the nonfortified 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 effect on the percentage of motile and abnormal sperm than diets inadequate in vitamin E. Sperm cells had a high concentration of Se and alpha-tocopherol, and a high GSH-Px activity. Experiment 3 was conducted using 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 reproductive tracts were recovered. The semen from boars fed the nonfortified Se diet had a lower fertilization rate of oocytes with fewer accessory sperm penetrating the zona pellucida. The results from these experiments indicate that dietary Se and vitamin E can affect boar semen quality, but the greater effect seemed to be from Se.