| Zinc is one of the essential trace elements for animals, and it participates in various physiological processes in vivo. Now the zinc added to animal feed is based on inorganic zinc sources, but because of its low utilization rate, 90% zinc is excreted with the feces, resulting in waste of resources and environmental pollution. Therefore, exploring a kind of organic zinc chelate which has low cost and simple preparation method is of great importance. In the recent years, many reports indicated that zinc-amino acid chelate could significantly improve the utilization of zinc, but few reports on preparing zinc-polysaccharide chelate with raw polysaccharides and inorganic zinc were published. Studies showed that chitooligosaccharides (COS) is a kind of polysaccharide with multifarious physiological activities, and there are a large number of free -NH2 and -OH in its molecule constructure, so it can selectively adsorb metal ions, and have a role of stable coordination to metal ions. This paper first identified the best conditions of preparing zinc-COS from raw materials chitooligosaccharides (COS) and zinc sulfate through the orthogonal experiment, and further had a further comparative study of some nutritional functions of zinc-COS, COS and zinc sulfate by animal experiment. Preparation of zinc-COS richs the sources of organic zinc and it is expected as a new zinc additive to improve the utilization of zinc.1. Mice fed by 30mg/kg (total zinc, the same below) zinc-COS have better average daily feed intake (ADFI) and average daily gain (ADG), the ADFl and ADG are enhanced respectively by 11.6% and 44.44% (P<0.01)), and F/G is reduced by 2.73%(P<0.01). Egg-chickens fed by 40mg/kg (total zinc, the same below) zinc-COS have better ADG, the ADG is increased by 5.86%% (P<0.05).2. The content of zinc in blood and liver of mice which were fed 30mg/kg zinc-COS are obviously higher by 54.59% and 33.37% (P<0.01) respectively. The contents of zinc in blood, liver, pancreas, ileum and leg muscle of egg- chickens which were fed 40mg/kg zinc-COS are significantly increased by 27.99%, 22.95%, 64.24%, 15.73% and 64.24% (P<0.01) respectively.3. Mice fed by 30mg/kg zinc-COS have better indices of thymus, spleen, liver and kidney, which were increased by 42.86% , 40.63%, 30.77% and 15.67% (P<0.05) respectively. The thymus, spleen and bursa indices of egg-chickens which were fed 40mg/kg zinc-COS are increased by 19.89%, 21.98% and 8.45% (P<0.01) respectively, and liver, kidney and left leg tibia indices are significantly increased by 12.16% 16.47% (P<0.05) and 17.43% (P<0.01) respectively.4. Zinc-COS can enhance the pregnant rate and weaning rate of female mice. Litter number, weaning number and weaning weight were significantly better than those in the zinc sulfate group, which are increased by 38.51% ,48.31% (P<0.05) and 32.12% (P<0.01). And the testis, ovary and uterus indices in the zinc-COS group are significantly increased by 15.43%, 33.33% and 29.39% (P<0.05) respectively.5. Antibacterial test showed that in the same concentration conditions, zinc-COS has obvious antibacterial activities against E. coli and Staphylococcus aureus than COS.6. Endurance test of mice showed that the swimming time of mice fed by zinc-COS is significantly longer than the mice fed by zinc sulfate and COS by 85.77% and 53.10% (P<0.01) respectively, the rerult showed that zinc-COS has obvious antifatigue effect.These results above suggested that the method of preparation of zinc-COS is simple with a low cost, and it has a better nutritional function than inorganic zinc(zinc sulfate) and COS, which also and shows a obvious synergies. Zinc-COS can be used as a new organic zinc sources used in animal production. |
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