The Effect Of High-level Copper And Zinc Addition On The Performance, Digestibilities And Gastrointestinal Enzyme Activities Of Weaned Piglets

The experiment was conducted to investigate the effect of high-level copper and zinc addition on the animal performance, nutrient digestibilities, and the activities of gastrointestinal amylase, protease, exogenous phytase and xylanase in weaned piglets. It was attempted to clarify the mechanism of growth promoting effect of high-level copper and zinc, and to verify the applications strategy of phytase and xylanase in high-level copper and zinc diet. The experiment included two parts:Experiment one, the effect of calcium, iron, copper and zinc on activities of amylase, pepsin, phytase and xylanase in vitro. The gradientis of ion concentration in the reaction medium was designed according to the normal and the highest level of the specific ions in commercial pig compound feed in China state of the art,and water content of digesta in the piglet gastrointestinal tract.The enzyme activities were measured in the sole ion concentration adjusted reaction medium at optimum temperature and pH conditions. The results showed that, Cu2+, Zn2+ and Fe2+ had strong inhibitory effects on amylase, and the inhibitory effects increased with increasing concentration, Ca2+ can activate the amylase,but the degree of activation did not change with the concentration; in the designed ion concentration gradients, the four ions all had the activation on pepsin, and the activation of almost all increased with increasing concentration. For phytase and xylanase, the inhibitory effects of Cu2+, Zn2+, Fe2+ increased with increasing concentration in the designed ion concentration gradients.Experiment two, the effect of high-level copper and zinc addition on the animal performance, nutrient digestibilities and the activites of gastrointestinal enzyme in weaned piglets. The based diet added phytase and xylanase, by 2×2 full factorial arrangement of treatment was employed with two levels of copper (20 and 250 mg/kg) and two levels of zinc (80 and 2500 mg/kg) to form four experimental diets named as control group (copper 20 mg/kg+zinc 80 mg/kg), high copper group (copper 250 mg/kg+zinc 80 mg/kg), high zinc group (copper 20 mg/kg+zinc2500 mg/kg), high copper and high zinc group (copper 250 mg/kg+zinc2500 mg/kg), Fourty-eight weaned piglets with body weight of (7.80±0.44) kg and age of (28d±3)-day-old were randomly allocated into 4 groups with 4 replicates and each replicate had 3 piglets, each group were randomly fed one experimental diet, to study the effects on performance, digestibilities, the activity of amylase, protease, phytase, xylanase in gastric and intestinal chyme with weaned piglets fed these four experimental diets. The results showed that, for ADG and F/G, the two levels of copper and zinc were significantly different (P<0.01), and there were interactions between copper and zinc (P<0.01); For ADFI, two levels of zinc had significant differences (P<0.05), the two levels of copper were not significant (P>0.05), there were no interactions between copper and zinc (P>0.05); for digestibilities of CP, significant differences were found between the two levels of copper and zinc (P<0.01),but there were no interactions between copper and zinc (P>0.05); for digestibilities of EE, significant differences were found between the two levels of copper and zinc (P<0.01), but there were interactions between copper and zinc (P<0.01); for utilization of EN, two levels of copper had significant differences (P<0.05), the two levels of zinc were not significant (P>0.05), there were no interactions between copper and zinc (P>0.05) When the activity of enzyme was expressed by per gram of chromium oxide chromium,statistical analysis showed that, in the two cases, the activity of pepsin was the same as that between the two levels of copper, significant differences were not found (P>0.05), between the two levels of zinc,there were significantly different (P<0.05), no interactions between copper and zinc (P>0.05); for the two cases of total protease, phytase in gastric and intestinal juice, intestinal xylanase, statistical analysis was the same as that no significant differences were found between the two levels of copper and zinc(P>0.05), no interactions between copper and zinc(P>0.05), the activiy of xylanase in gstric chime showed that the two levels of copper and zinc were not significant(P>0.05), but the interactions between copper and zinc(P<0.05). Amylase had different statistical analysis in two cases, when at uncorrected ion concentration, both copper and zinc levels were not significant(P>0.05), no interactions between the two (P>0.05), when at corrected ion concentration, two levels of copper were significantly different (P<0.05), two levels of zinc were very significantly different (P<0.01), and interactions between copper and zinc (P<0.05).