اثر منابع روی بر عملکرد، گوارش پذیری و شاخص‌های آنتی اکسیدانی خون در بزهای نر مورسیا

Abstract
Background and objectives: Goat as a multipurpose animal is crucial for economy and food supply for urban and rural communities. Zn is one of the most restricted trace minerals, which should be included in the diet of ruminants on a daily basis. Researches have shown that more growth performance improvement is obtained by adding organic or nanoparticles of Zn compared to ZnSO4. According to the researches, feeding different sources of Zn improves the digestibility of nutrients. In studies which Zn supplement was added to diets, the antioxidant status of the trial animals was improved. Moreover, various sources of Zn have divers’ bioavailability and few studies have been conducted on the effects of different sources of Zn on body weight change, nutrients digestibility and antioxidant status of goats, this experiment was carried out to investigate the effect of zinc sources on performance, digestibility and blood antioxidant indices in Murciana bucks.
Materials and methods: Forty Murciana bucks (with an average age of approximately 1.5 year and an average body weight of 43±1.54 kg) were applicated for sixty days in a completely randomized design model. The animals were randomly assigned into 4 experimental treatments and 10 replications, which included: 1) basal diet (containing 19.95 mg kg-1 Zn without supplementation), 2) basal diet containing 32 mg kg-1 Zn as ZnSO4, 3) basal diet containing 32 mg kg-1 Zn as ZnMet, 4) basal diet containing 32 mg kg-1 Zn as nanoparticles and livestock had free access to water. Blood samples were collected by jugular vein puncture containing anti-coagulant agent on day 60 of the experiment. Chemical analysis of feed samples was adjusted through standard laboratory methods for dry matter, ash, crude protein, ether extract, and neutral detergent fiber. Apparent digestibility of nutrients was determined through acid-insoluble ash method. The activities of plasma enzymes were measured using commercial kits and through the ELISA device. All data were analyzed through the statistical model of completely random design and by the analysis of variance method.
Results: In this research, feeding Zn supplement improved the average daily gain, average daily feed intake and feed conversion ratio (P≤ 0.05). Moreover, the administration of Zn supplement regardless of its source, improved the apparent digestibility of crude protein, organic matter and neutral detergent fiber (P≤ 0.05). The plasma concentrations of alkaline phosphatase and superoxide dismutase enzymes in the treatments fed with Zn supplements were increased compared to the control group (P≤ 0.05), but the plasma concentrations of malondialdehyde, aspartate aminotransferase and alanine aminotransferase enzymes were decreased significantly in the animals fed Zn supplements (P≤ 0.05).
Conclusion: Feeding various types of Zn supplements (organic, inorganic and nanoparticles) under marginal deficiency situations for Zn in animals, will cause positive effects on compensatory gain, improvement of feed conversion ratio, nutrients digestibility, and promotion of the antioxidant system of the body. Because in the conditions of marginal deficiency of trace minerals, the absorption mechanisms of the body become more active in order to improve the absorption of these elements, and therefore, probably for this reason, no significant difference was observed between different sources of Zn in this research. Therefore, by consideration to the cost of feed, the treatment fed ZnSO4 is cost-effective, especially when the animal is in marginal zinc deficiency condition, because it increased nutrient digestibility, optimal production performance and improved antioxidant status similar to the expensive sources used in ZnMet and Zn-nanoparticles treatments.