The Study Of A Exogenous Protease (ProAct) On Performance And Amino Acids Digestibility In Broiler Chicken

This thesis was conducted to study the effect of exogenous protease (ProAct) on the production performance, amino acid metabolism, endogenous protease activity, the development of digestive organ, intestinal morphology and serum biochemical of broilers, in order to provide theoretical foundation of reasonable application of enzymes in poultry diets. The research will be carried out as the following three parts. Effects of exogenous dietary protease on:1) performance and amino acid apparent digestibility;2) digestive enzyme activity, development of digestive organ; intestinal morphology;3) blood biochemical index, antioxidation competence and immune organ index of broilers.Experimental DesignCorn-soybean meal-and meat and bone meal-based broiler diets would be used in the study. Six hundred and sevevty two7-day-old healthy broilers (Arbor Acres) with a similar body weight were randomly allocated to6treatments with8replicates in each treatment and14chickens per replicate. Broilers in the control group (PC) were fed a basal diet, and broilers in the experimental groups include four groups which were fed the basal diet(PC) supplemented with0.01%,0.02%,0.04%and0.08%protease respectively, and one group which were fed a reduced AME and CP diet (NC) plus0.02%ProAct. The trial lasted for35days (8d-21d and22d-42d)ResultsEffects of exogenous dietary protease on performance and amino acid apparent digestibility of broilers.1) Adding0.02%ProAct to low protein diet can promote the growth performance of broiler chickens, but the feed efficiency is slightly lower (P>0.05).2)At the age of8to21days, fodder with protease significantly improved the average daily feed intake (P<0.01), and the supplementation of0.02%protease increase the average daily gain (P<0.10);3) The supplementation of0.01%～0.02%ProAct can improve the production performance, when the addition amount is0.01%, it can promote the growth, when the addition amount reached0.02%it not only can promote growth but also improve the feed efficiency of broilers.4) At the age of21days, adding0.02%ProAct to the normal diet can significantly increase (P<0.05) the digestibility of crude protein, glycine, and methionine of broiler chickens.Effects of exogenous dietary protease on digestive enzyme activity and intestinal morphology of broilers. The results showed as follows.1) Diet ProAct can inhibiting the activity of trypsin and chymotrypsin in pancreas and promote the activity of endogenesis protease in the intestinal;2)0.02%ProAct benefits digestive organ development, While the high dose of the enzyme (0.08%) against the digestive organ development;3) The intestinal villus height of jejunum was improved (P<0.01) and the crypt depth of jejunum and ileum are reduced(P=0.062)in a quadratic manner as ProAct was increased.4) The chicken in the0.02%ProAct treatment have the hightest intestinal villus and the largest ratio of intestinal villus height and crypt depth (V/C). But a high dose of ProAct (0.08%) can reduce the V/C of the21days old chicken and reduce the intestinal villus height at42d. So that,0.02%ProAct supplementation benefits the intestinal development in the early age of the broilers,0.08%ProAct is not conducive to the formation of a good tissue morphology of the small intestine.Effects of exogenous dietary protease on blood biochemical index, antioxidation competence and immune organ index of broilers.1)No significant differences were showen on blood biochemical indexes between treatment (P>0.05), it indicates that the diet ProAct had no adverse effect on the serum biochemical metabolism;2) the total antioxidant power (T-AOC) of treatment PC (0.01%ProAct) was improved;3) there is no significant difference of the immune organ index between each group(P>0.05).ConclusionAdding0.02%ProAct to low protein diet (1%crude protein and20kcal/kg metabolic energy lower)can promote the growth of broiler chickens, but the feed efficiency is slightly lower; Adding0.01%-0.02%ProAct to normal diet can improve the production performance of broilers and improve the feed efficiency when the additive amount is0.02%. ProAct can improve the digestibility of crude protein and part of amino acid in the diet, inhibit pancreatic trypsin and chymotrypsin activity and promote the intestinal protease activity; There is no adverse effect of adding ProAct to the diet on the antioxidant system, plasma biochemical metabolism of broilers, and it can promote the development of immune organs. In conclusion, the suitable addition amount to the diet is0.01%～0.02%.