بررسی اثر منابع مختلف روی بر عملکرد تولید مثلی و برخی از فراسنجه‌های خونی در بزهای نر بالغ مورسیا

Abstract
Background and objectives: Goat as a multipurpose animal is crucial for the economy and food supply for urban and rural communities. Zinc is one of the most restricted trace minerals, which should be included in the diet of ruminants on daily. Research has shown that the use of organic or zinc nanoparticle supplements compared to inorganic supplements causes the stability of the sperm membrane and reduces oxidative damage, as well as improves the preservation of the integrity of the sperm membrane. Studies conducted in humans, mice, dogs, cows and goats showed that zinc chelates are more effective in maintenance, stability, motility and attachment of head to tail of spermatozoa. Also, since different sources of zinc have different bioavailability and there are few studies about the effects of different sources of zinc on the reproductive attributes in bucks, the present experiment is to investigate the effect of different sources of zinc on reproductive performance and some blood parameters in Murciana bucks.
Materials and methods: Forty mature Murciana bucks (with an average age of approximately 1.5 years and an average body weight of 43±1.54 kg) were applied for a 60-day experiment in a completely randomized design model. The animals were randomly assigned into 4 experimental treatments with 10 replications, which included: control (containing 19.95 mg kg-1 Zn without supplementation), 32 mg
kg-1 ZnSO4, 32 mg kg-1 ZnMet, and 32 mg kg-1 nano-Zn. Blood samples were collected by jugular vein puncture containing an anti-coagulant agent before morning meal on days 30 and 60 days of the experiment. Chemical analysis of feed samples was adjusted through international instructions for dry matter, ash, crude protein, ether extract, and neutral detergent fiber. Ejaculate volume was evaluated in a graduated glass tube that was adjusted to the artificial vagina. Moreover, the concentration of sperm to each ejaculation was carry out by a hemocytometer chamber through an optical microscope. The Eosin-Nigrosin stain was utilized to calculate the proportions of live, dead and abnormalities including head, mid-piece and tail. The CASA computer software was used to evaluate sperm motility characteristics according to reference guidelines. The ELISA method measured plasma testosterone concentration using a commercial kit. Plasma samples were digested with hydrochloric acid and then the concentrations of Fe, Zn and Cu were determined by a flame atomic absorption spectrometry. Semen quality and quantity traits were analyzed by completely randomized design (CRD) using the Proc GLM. Blood testosterone concentrations were analyzed as repeated measures in a completely randomized design using the Proc MIXED.
Results: In this research, Zn supplementation caused an increase in ejaculate volume, sperm concentration, viability, sperm membrane integrity, sperm morphology and some sperm velocity characteristics (P ≤ 0.05). Also, no significant difference was observed between the quantitative, qualitative, motility and morphological characteristics of sperm among the source of Zn supplements (ZnSO4, Zn-Met, nano-Zn) (P > 0.05). The Zn plasma concentration and testosterone were improved in the treatments fed Zn supplements compared to the control group (P ≤ 0.05), but no significant difference was observed between the plasma concentrations of Cu and Fe (P > 0.05).
Conclusion: Feeding various types of Zn supplements (organic, inorganic and nanoparticles) improved the reproductive performance of Murciana bucks, which seems to be probably due to the lack of sufficient amounts of Zn in the diets. Considering the amount of zinc in the basal diet and the conditions of this experiment, it is suggested to use zinc sulfate in rations to improve reproductive performance and feed cost management.