The effect of different levels of zinc on performance and retention of some mineral elements in Mehraban male lambs

Background and objectives: Zinc (Zn) is one of the trace elements that affects in the growth, reproduction and improvement of the immune system of animals. Recently, Zn has been supplemented to the diet for increasing the performance of livestock. However, supplementation with excessively of Zn to the diet may, decrease performance, affect the absorption and retention of other mineral elements. The present study was conducted to investigate the effect of different levels of Zn in form of inorganic, on performance and concentration of some blood mineral elements and their retention in Mehraban male lambs.
Materials and methods: To conduct this experiment, 18 Mehraban male lambs with an average age of 3-4 months and an initial body weight of 33.62 ± 2.67 kg were assigned to 3 treatments with 6 replicates each, as a completely randomized design. Experimental treatments included 1) control group (basal diet, without supplementation of Zn), treatment 2) basal diet plus 40 mg Zn/kg DM in the form of zinc sulfate and treatment 3) basal diet plus 80 mg Zn/kg DM in the form of zinc sulfate. During the experimental period (60 days), feed intake and body weight gain were measured daily and every 15 days, respectively. The blood samples were taken from the lambs via the jugular vein, on the day 60 at before feeding morning. Then, 4 lambs from each treatment were randomly selected and transferred to the metabolic cages. Considering a 5 days for adaptation period, fecal and urine samples of the lambs were collected for 5 days for mineral balance trial. The chemical composition of diet compounds, feces, urine and blood minerals (zinc, calcium, phosphorus, iron, and copper) were determined using standard methods.
Results: The results showed that the supplementation of zinc in the diet had no effect on dry matter intake. However, its effect on daily weight gain and feed conversion ratio was significant (P<0.05). Accordingly, the daily weight gain in lambs in control group and treatments 2 and 3 was 241.07, 269.35 and 273.81 g/d, respectively. Also, zinc supplementation significantly increased the level of zinc in the blood of lambs (P<0.05), and its value increased from 0.86 mg/L (in the control group) to 1.24 and 1.13 mg/L in treatments 2 and 3, respectively. Retention of zinc in body was affected by zinc supplementation (P<0.05), and its value were 3.40, 6.14, and 5.82 mg/d in control group and treatments 2 and 3, respectively. However, the retention of other measured mineral elements was not affected by zinc supplementation. The correlation between zinc retention and other mineral elements was not significant.
Conclusion: Generally, the results showed that supplementation of 40 and 80 mg Zn/kg DM to the diet of lambs improved the performance (daily weight gain). Also, the concentration of zinc in the blood and its retention in the body were affected by the supplementation of zinc.