Effects of Dietary Selenium and Vitamin E Supplementation on Growth Performance, Blood Biochemistry, Antioxidant Status, Immunity and Semen Quality of Male Turkeys Reared Under Chronic Heat Stress

Abstract

Heat stress impairs growth and fertility in male turkeys, largely through oxidative damage to metabolically active tissues and to spermatozoa. This study evaluated whether graded, supranutritional combinations of selenium (Se) and vitamin E could protect the productive, metabolic, antioxidant, immune and reproductive functions of male turkeys exposed to chronic cyclic heat stress. Fifty-four 30-week-old male turkeys were allotted to six dietary treatments (three replicates of three birds each): a basal diet (T1, control) or the basal diet supplemented with 0.3, 0.5, 0.7, 1.0 or 1.2 mg/kg Se combined with 100, 200, 300, 400 or 500 mg/kg vitamin E (T2–T6, respectively) for eight weeks, during which the birds were exposed to 36 ± 2 °C for 8 h daily. Body weight, feed intake, feed conversion ratio (FCR), serum biochemical indices, superoxide dismutase (SOD) activity, malondialdehyde (MDA), reduced glutathione (GSH), immunoglobulin G (IgG), plasma testosterone and semen characteristics were determined. Moderate supplementation (T2 and T3) produced the highest body weight at 34 weeks and the lowest FCR (P < 0.05), whereas the highest inclusion levels (T5 and T6) depressed growth and increased FCR relative to the control. Supplemented birds, particularly T3–T5, showed higher SOD activity and lower MDA, and T2–T3 had the lowest serum glucose, total lipids and cholesterol together with the highest total protein, albumin and IgG. Plasma testosterone, sperm concentration and progressive motility were greatest, and the percentage of abnormal spermatozoa lowest, in T3 and T4 (P < 0.05), whereas T6 was not superior to the control for any reproductive trait. Combined supplementation with 0.5–0.7 mg/kg Se and 200–300 mg/kg vitamin E therefore represents an effective nutritional strategy for protecting antioxidant status and semen quality in heat-stressed male turkeys, with no additional benefit, and possible adverse effects, at higher inclusion levels.