Oral suplementation with selenium for young Brangus bulls raised in pasture: seminal quality in fresh and frozen semen
Cryopreservation stimulates production of free radicals and oxidative stress. The selenium (cofactor of enzyme glutathione peroxidase) acts as antioxidant protecting sperm membrane of lipid peroxidation and against consequent loss of function. The aim of this study was to evaluate oral selenium supplementation on semen quality of fresh and cryopreserved semen from young Brangus bulls raised in pastures in central Brazil. Sixteen Brangus bulls (5/8 Angus 3/8 Zebu) with 24 months and 472 kg of body weight on continuous grazing with daily concentrate supplementation by 75 days were used. The treatments were: GC- control (no added selenium in concentrated supplementation), GS - selenium (concentrated with addition of 0.1 mg Se/kg of dry matter intake (DMI)). After collection were evaluated sperm motility (MOT), sperm vigor (VIG), sperm viability (SVIAB), spermatic membrane integrity (SMI) and acrosomal membrane integrity (AMI) and triple stain (TS). Then semen was diluted and cryopreserved in TRIS-egg yolk citrate extender with 4% of glycerol. Thawing was performed in water bath at 37°C for 30 seconds. After thawing the samples, aliquots to evaluation of MOT, VIG, SVIAB, SMI, AMI and TS were removed. Experiment was conducted in a completely randomized design. Data were analyzed by ANOVA with significance level of 5%. Supplementation with selenium improved SMI (P=0.0480) in fresh semen (CG 26.71±2.89 vs 37.45±4.14 GS) and frozen semen (GC 8.75±1.42 vs. GS 9.90±1.59). Selenium supplementation did not altered other parameters evaluated (P>0.05). Studies on selenium supplementation with qualitative and quantitative parameters of bovine semen are rare. Thus, further research should be done to better understand effect of selenium on reproductive function. Oral supplementation with selenium concentration of 0.1 mg/kg DMI for young Brangus bulls raised on pasture, does not alter seminal parameters traditionally evaluated in fresh and cryopreserved semen, however, improves integrity of sperm plasmatic membrane.
Keywords: antioxidant, cryopreservation, sperm membrane.