摘 要：
The experiment was conducted to study the effects of different levels of coated compound trace elements(CCTE) on growth performance, serum antioxidant and immune indicators of Yunnan semi-fine-wool sheep during growing period. Fifty healthy 5-month-old Yunnan semi-fine-wool rams were randomly divided into 5 groups based on body weight, with 10 sheep in each group. The animals in the control group(Group Ⅰ) were fed a basal diet, and the animals in the experimental groups(groups Ⅱ, Ⅲ, Ⅳ, Ⅴ) were fed the basal diet supplemented with 200, 400, 600, and 800 mg/kg, respectively. The pre-trial period was 10 days, and the trial period was 30 days. On the 1st and 30th days of the experiment, the experimental sheep were weighed on an empty stomach, and dry matter intake(DMI), average daily gain(ADG), and feed weight ratio(F/G) were calculated. On the 15th and 30th days of the trial, five sheep were randomly selected from each group to collect blood and isolate serum for the detection of serum trace element indicators(iron [Fe], copper [Cu], manganese [Mn], zinc [Zn], selenium [Se], iodine [I], and cobalt [Co]), serum antioxidant indicators(total superoxide dismutase [T-SOD], catalase [CAT], and malondialdehyde [MDA]) and serum immune indicators(immunoglobulin A [IgA], immunoglobulin G [IgG], immunoglobulin M [IgM], complement C3, complement C4, and endotoxin [ET]). Significance analysis, linearity and quadratic effect analysis were carried out on the detection results. The results showed that there was no significant difference in DMI among the groups(P>0.05), and there was a quadratic relationship between ADG and F/G and the addition level of CCTE(P_Q<0.05), among which ADG was the highest and F/G was the lowest in group Ⅲ. On the 30th day of the experiment, there was no significant difference in the mass concentrations of serum Fe, Cu and Mn among all groups(P>0.05), but the mass concentrations of serum Fe, Zn, Se, I, and Co were linearly increased with the increase of CCTE addition level(P_L<0.05). There was no significant difference in serum T-SOD activity among all groups(P>0.05). The serum CAT activity in Group Ⅰ was the lowest, and the serum MDA concentration in Groups Ⅱ, Ⅲ and Ⅳ was significantly lower than that in Groups Ⅰ and Ⅴ(P<0.05). There was a quadratic relationship between serum MDA concentration and CCTE addition level(P_Q<0.05), and the MDA concentration was linearly increased with the increase of CCTE addition level(P_L<0.05), among which the serum MDA concentration in Group Ⅲ was the lowest. The mass concentrations of IgA, complement C3, complement C4 and ET activity in sheep serum showed linear relationship(P_L<0.05) and quadratic relationship(P_Q<0.05) with the supplemental level of CCTE, among which the mass concentrations of IgA, IgG, IgM, complement C3, and complement C4 in Group Ⅲ, and the content of ET in group Ⅴ were the highest, while that in Group Ⅲ was the lowest. The results indicated that adding 400 mg/kg of CCTE could improve the antioxidant capacity and immune performance of sheep, but has little impact on sheep growth performance. Under the experimental conditions, adding 400 mg/kg of CCTE were the best supplemental level in Yunnan semi-fine-wool sheep feed in the growth period, and the supplemental levels of Fe, Cu, Mn, Zn, Se, I, and Co were 48.00, 6.40, 20.00, 34.00, 0.32, 0.40, and 0.32 mg/kg, respectively.
