| Trace element Zn is one of the most important essential trace elements for animals, it affect nearly 300 kinds of enzymatic activity in vivo as an important part of enzyme and the activator (Pang Quanhai et al., 2002), it extensive involvement and regulate the metabolic activity of organism,and it participate in the metabolism of DNA, RNA, protein, carbohydrate, lipid, vitamin and mineral. Zn not only can maintain skeletal growth, epithelial cell integrity and hormone in normal adjustment and also can boost the immune and reproductive capacity of organism, Zn was known as the "life element*. In recent years, with the intensive study of Zn, more zinc finger protein and zinc containing enzymes were found out. At the same time, the mechanism of disease caused by zinc deficiency on animal were more clear-cut, existing form and function of tissues and organs of zinc were also more specific. Therefore, to study the effect of dietary zinc levels on the growth performance, digestion and metabolism of mink, nitrogen metabolism, serum biochemical index, immune function, anti-oxidation performance and organ coefficient in mink, we added different concentration of zinc sulfate in the diet. And to explore the effect of mechanism of zinc on growth performance, nutrient metabolism in mink. At the same time, in order to provides the scientific evidence to improve China’s feeding standard in mink. To explore the mechanism of zinc nutrition in mink in vivo lay the foundation.1. The experiment was preceded by a 7-day adjustment period, during which the animals were accustomed to the experimental feed. The animals were fed ad libitum a conventional mink feed supplied by the local feeding kitchen and housed individually in cages, at 8:00 am and 13:00 pm daily. The diet was formulated to meet the nutrient requirements of NRC (1982) for mink. The composition of diets used in the experiment are shown in Table 1. Seventy-five healthy male minks were randomly assigned to one of five groups; each group consisted of 15 minks. Group 1 was the control and was fed the basal diet, group 2 was fed the basal diet supplemented with 50 ppm Zn (0.137 g/kg ZnSO4.H2O), group 3 was fed 100 ppm Zn (0.275 g/kg ZnSO4. H2O), group 4 received 300 ppm Zn (0.826 g/kg ZnSO4. H2O), and group 5 received 600 ppm Zn (1.65 g/kg ZnSO4.H2O). The supplementation period lasted 80 days from middle September to pelting. The body weight of minks was confirmed at the beginning and end (pelting) of the experiment, and average daily gain (ADG), average daily feed intake (ADFI), and the ratio of feed to weight gain (F/G) were calculated. Effects of diets with different Zn levels of serum biochemical indices in minks. Diets with different Zn levels was a significant effect of Zn level on ADG and ADFI in minks(P<0.05).2. N-balance experiments were carried out using 152-day-old mink from each treatment group. The f eces and urine collection period lasted 4 days (10th to 13th October 2013). As described by J(?)rgensen and Glem-Hansen (1973), the animals were kept in metabolism cages constructed for separate collection of feces and urine. To prevent ammonia evaporation from the urine,10 ml sulphuric acid (10% solution) were added to the urine collection bottles and the urine collection trays were sprayed with citric acid (10% solution) once daily. In the process of calculating the N-balance, retained N was calculated as ingested N-(fecal N+ urinary N). The chemical composition of the diets, feces, and urine was analyzed by standard methods. Dry matter (DM), ash, crude protein (CP) (Kjeldahl-N, 6.25), calcium, and phosphorus contents were analyzed according to AOAC (2003) procedures. crude carbohydrate (CC) was calculated by subtracting ash, CP, and digestibility of ether extract (EE) from the DM content. The calculation of metabolic energy (ME) content and the proportional composition of ME were based on the digestibility coefficients achieved and were the following:18.8 MJ/kg protein,39.8 MJ/kg fat, and 17.6 MJ/kg carbohydrate (Hansen ed at.1991). The calculation of gross energy (GE) content was based on the average combustion values of macro nutrients: 23.86 MJ/kg protein,39.76 MJ/kg fat, and 17.58 MJ/kg carbohydrate (Lass en et al.2012). The concentrations of Zn, copper, and manganese were determined by Atomic Absorption spectrophotometry (Analytik Jena NOV AA 400). Effects of diets with different Zn levels of serum biochemical indices in minks. Diets with different Zn levels was a significant effect of Zn level on DM Digestibility and CC Digestibility in minks(P <0.05).3. At the end of the experimental period (at pelting), eight minks were randomly selected to be slaughtered. Blood samples were collected in anticoagulating substance tubes. Samples were quickly transferred to the lab where serum was obtained by centrifuging the tubes for 15 min at 3,000rpm. Serum was frozen at-20℃ for later analysis of Albumin (Alb), Total Protein (TP), Globulin (GLOB), Usea nitrogen (UN), Aspartate Transaminase (AST), Alanine transaminase (ALT), alkaline phosphatase (ALP), Lactate dehydrogenase (LDH), Ca, P and Zn by an automatic biochemistry analyzer (Vitalab E, Vitalab Hitachi Global Storage Technologies, Netherlands). Effects of diets with different Zn levels of serum biochemical indices in minks. Diets with different Zn levels was a significant effect of Zn level on serum Nitrogen Metabolism, alkaline phosphatase, P and Zn level in minks(P<0.05).4. At the end of the experimental period (at pelting), eight minks were randomly selected to be slaughtered. Blood samples were collected in anticoagulating substance tubes. Samples were quickly transferred to the lab where serum was obtained by centrifuging the tubes for 15 min at 3,000 rpm. Serum was frozen at-20" C for later analysis of immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM) by an automatic biochemistry analyzer (Vitalab E, Vitalab Hitachi Global Storage Technologies, Netherlands). The concentrations of serum IgA, IgG, and IgM were tested with commercially available assay kits purchased from Biochemical Corporation and Biosino Bio-Technology and Science, Inc (Biochemical Corporation and Biosino Bio-Technology and Science, Inc, Beijing, China). Serum IgA and IgM levels for III, IV, and V were significantly higher than those of I and II (P< 0.01). However, supplemental dietary Zn did not affect serum IgG levels (P> 0.05)5. At the end of the experimental period (at pelting), eight minks were randomly selected to be slaughtered. Blood samples were collected in anticoagulating substance tubes. Samples were quickly transferred to the lab where serum was obtained by centrifuging the tubes for 15 min at 3,000 rpm. Serum was frozen at-20℃ for later analysis of glutathione peroxidase (GSH-PX), catalase (CAT), superoxide dismutase (SOD), Cu-Zn superoxide dismutase (Cu-Zn SOD), and malondialdehyde (MDA) by an automatic biochemistry analyzer (Vitalab E, Vitalab Hitachi Global Storage Technologies, Netherlands). The Zn100 and Zn300 groups had higher CAT content in serum compared with that of ZnO and Zn50 (P<0.05). Compared with the control, the Zn300 group had higher levels of SOD in serum (P <0.05). Moreover, Cu-Zn SOD from group ZnO was higher than groups Zn100 and Zn300 (P< 0.05). Serum MDA levels of groups Zn600 and Zn100 were higher than that of group Zn300. There was a significant effect of Zn level on serum GSH-PX level (P< 0.01); the Zn300 group had the highest serum GSH-PX level, the ZnO group had the lowest.7. Real-time PCR was used to analyse the change of mRNA expression level of TYRP1.TYRP2 and TYRP gene between mink. The mRNA levels showed these genes were differentially expressed genes, the values of TYRP1 and TYRP2 gene retention had a trend towards increasing initially and then decreasing as dietary Zn levels increased; the highest values were observed in group III. TYRPland TYRP2 gene were significantly higher than those of Other groups. |
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