Effects Of Zinc-Bearing Clinoptilolite On Digestive Function, Metal Element Deposition In Tissues, Meat Quality, Liver Antioxidant Capacity Of Broiler Chickens

This study was conducted to evaluate the effect of zinc-bearing clinoptilolite (ZnCP) addition on growth performance, digestive enzyme activity, intestinal morphology, blood biochemical parameters, metal deposition in tissues, meat quality, antioxidant function and related genes expression of broiler chickens, to explore the possibility of ZnCP as an antibiotic alternative, and preliminarily to determine the appropriate level of ZnCP in feed. This study would provide a theoretical reference for the application of ZnCP. The thesis was divided into four parts as follows:The fist experiment was conducted to study the impact of ZnCP on growth performance, nutrient utilization and blood biochemical parameters of broiler chickens. A total of 300 one-day-old Arbor Acres chickens were randomly allocated into 5 groups with 6 replicates of 10 birds for a 42-d feeding trial. The dietary treatments were as follows:1) control (CON) fed a basal diet with 60 mg/kg zinc from zinc sulphate; 2) the basal diet plus antibiotics (ANT,40 mg chlortetracycline per kg of diet); 3) the basal diet plus 0.1% ZnCP; 4) the basal diet plus 0.2% ZnCP; 5) the basal diet plus 0.4% ZnCP. The results showed that compared to CON, ZnCP treatments caused positive effects on BWG (P<0.05) of broilers during 1-21 d. Compared to ANT, the contents of GLU and TC in serum were increased by 0.4% ZnCP at 21 d (P<0.05), and TC contents in serum were reduced by 0.2% and 0.4% ZnCP at 42 d (P<0.05).0.2% ZnCP supplementation significantly improved 21 d T4 and 42 d INS contents in serum (P<0.05), and 0.4% ZnCP supplementation significantly increased T3 contents in serum at 21 d (P<0.05). Compared to ANT, T3 contents in serum at 42 d was raised by 0.2% ZnCP (P<0.05).Experiment 2, the objective of this experiment was to study the effect of zinc-bearing clinoptilolite on digestive enzyme activity, jejunal mucosa disaccharidase activity and intestinal morphology.The trial design and materials were the same as that in the first experiment. The results showed that compared to CON and ANT, the activity of pancreatic and intestinal amylase was improved significantly by the 0.2% and 0.4% group at 21d (P<0.05). Compared to CON,0.2% and 0.4% ZnCP supplementation significantly improved sucrase activity in jejunal mucosa at 42 d (P<0.05),and 0.1% ZnCP supplementation significantly increased trypsin and amylase activity in pancreas at 21 d and 42 d respectively (P<0.05),and the 21 d intestinal contents lipase activity was improved by ZnCP (P<0.05),and the 42 d intestinal contents amylas activity was increased by 0.4% ZnCP (P<0.05),and 0.2% and 0.4% ZnCP supplementation significantly improved trypsin activity in intestinal contents at 42 d (P<0.05), and antibiotic had significantly effects on sucrase activity in jejunal mucosa at 42 d and lipase activity in intestinal contents at 21d (P<0.05).0.2% and 0.4% ZnCP treatments caused positive effects on villus height in duodenum and jejunum of broilers at 21 d (P<0.05), and significantly reduced crypt dept in 42 d duodenum and 21 d jejunum (P<0.05).0.2% ZnCP treatments caused positive effects on V/C value in 42 d duodenum and 21 d jejunum (P<0.05),and the villus height in duodenum was reduced by antibiotic treatment at 21 d (P<0.05). Compared to ANT,0.2% and 0.4% ZnCP supplementation significantly improved villus height in jejunum and duodenum,and V/C value in duodenum in 21 d (P<..05).Experiment 3, the objective of this experiment was to study the effect of zinc-bearing clinoptilolite on metal content and meat quality of broiler. The trial design and materials were the same as that in the first experiment. The results showed that:0.2% and 0.4% ZnCP supplementation significantly improved the concents of Zn and Fe in pancreas (P<0.05), and the concents of Mg and Cu in pancreas was increased by 0.2% ZnCP at 21 d (P<0.05). ZnCP supplementation had the trend of improving Zn concent in liver at 42 d (P=0.08). There were no significant effects of ZnCP on the pH45min, pH24h, cooked rate, L* value, b* value in breast and thigh muscle, and drip loss、pressure loss in breast muscle at 24 h (P>0.05). ZnCP supplementation significantly reduced drip loss in breast muscle at 48 h (P<0.05), and 0.2%ZnCP treatment had a lower value than ANT (P<0.05). Compared to CON and ANT, the a* value in breast muscle was improved by 0.2% and 0.4% ZnCP treatments (P<0.05).Experiment 4 was conducted to evaluate the effect of ZnCP addition on antioxidant function, MT3, MT4, Nrf2, CuZn-SOD, GPX genes expression in liver. The trial design was the same as that in the first experiment. The results showed that compared to CON, the activities of T-SOD and Cu-Zn SOD in liver were increased by 0.1% and 0.2% ZnCP at 21 d (P<0.05). MDA contents in liver at 21 d were reduced by 0.2% ZnCP (P<0.05). ZnCP and antibiotic treatments increased T-AOC in liver at 21 d (P<0.05).Compared to ANT, 0.1% and 0.2% ZnCP reduced MDA contents (P<0.05) and increased T-SOD activity in liver at 21 d (P<0.05). Nrf2 mRNA level in liver was upregulated by 0.1% ZnCP at 42 d (P<0.05). Compared to CON and ANT,0.2% ZnCP improved MDA contents in liver at 42 d (P<0.05), and 0.2% and 0.4% ZnCP significantly improved MT3 mRNA level in liver at 42 d (P<0.05).