Effect of dietary antioxidant supplementation on fresh semen quality in stallion

In this study, the effect of dietary supplementation of organic selenium, vitamin E, and zinc on raw semen characteristics was evaluated. Ten stallions with normal fertility were divided into two groups: a control group (CG), in which standard diet was provided, and a treated group (TG), in which the standard diet was supplemented with 1500 mg of α-tocopherol acetate, 360 mg of zinc, and 2.5 mg of organic selenium on a daily basis. Semen parameters on fresh semen were evaluated three times in all stallions before antioxidant supplementation (T0) and 30 (T1), 60 (T2), and 90 (T3) d after supplementation. Dietary supplementation with experimental antioxidants resulted in a significant increase in average path velocity (121.9 ± 3.1 μm/sec in TG vs 118.9 ± 4.3 μm/sec in CG), straightness (86.2 ± 2.4 % vs 82.6 ± 3.9 % in TG and CG respectively), viability (75.6 ± 10.2 % in TG vs 72.3 ± 6.9 % in CG) and total seminal plasma antioxidants levels (2.7 ± 0.5 mmol/l vs 1.9 ± 0.4 mmol/l in TG and CG respectively) while progressive motility 69.7 ± 11 % vs 62.2 ± 9.3 % in TG and CG stallions respectively) and abnormal sperm morphology (8.2±1.5 % in TG vs 14.4±4 % in CG) significantly improved in treated stallions after 60 d of supplementation. In contrast with previously reported in other species, a negative effect of antioxidant supplementation on semen concentration was recorded in the TG. A positive correlation between progressive motility and total antioxidants in seminal plasma in both treated and control stallions suggested that motility is affected by oxidative-antioxidative status, and that dietary antioxidant supplementation could increase the ability of spermatozoa to contrast reactive oxygen species or the ability of seminal plasma to reduce the oxidative stress. The improvement of semen parameters after antioxidant supplementation was not linear, and after 30 d (or 60 d for some parameters), a further increase was not noted. This evidence suggested that in our standard conditions, dietary intake of these antioxidants could be slightly under the dietary requirement and further evaluation of the actual nutrition requirements of organic selenium, zinc, and vitamin E in the stallion are needed.