Effect of Zinc Supplementation to Diluent Boar Semen on Sperm Characteristics and Activity of Antioxidant Enzymes

Abstract

Background. Zinc is essential for male reproductive function as it is necessary for spermatozoa maturation, capacitation, acrosome reaction, and fertilization. It has been established that the use of chelates compounds of metals with amino acids, nucleotides, peptides, and carbohydrates is not only more effective but also economically justified. Objective. The aim of this study was to evaluate and compare the effect of different concentrations of Zn glutamic amino acid chelate (ZnGlu) on boar spermatozoa motility, viability parameters, and prooxidant-antioxidant homeostasis during in vitro incubation. Methods. Freshly ejaculated boar semen, after the addition of "Ecosperm" diluent, was divided into groups: a control group and three experimental groups. Zinc glutamate was supplemented to the experimental samples at concentrations of 1.0, 2.0, and 5.0 µg/ml, respectively. Semen samples were stored at 18 °C for 4 days. Every 24 hours, sperm motility and viability and the antioxidant status were assessed by the level of diene con­jugates (DC), concentration of malondialdehydere (MDA), and the activities of catalase and superoxide dismutase. Results. It was observed that boar sperm motility decreased with the extension of storage time, while the addition of 2.0 and 5.0 µg ZnGlu significantly improved sperm total motility and the percentage of vitality spermatozoa during 48–96 hours of incubation. Our studies also demonstrate that ZnGlu possess a protective effect in alleviating oxidative stress in boar sperm in vitro. The addition of ZnGlu significantly reduced the content of MDA and DC in ejaculate samples in all experimental groups during incubation, compared to the control group. Moreover, the activity of superoxide dismutase and catalase increased after adding ZnGlu to the boar semen, especially at concentrations of 2.0 and 5.0 mg/ml (P < 0.05). Conclusions. These data demonstrate that the supplementation of zinc glutamate enhances the antioxidant defence system of sperm and improves quality of boar semen in vitro.