Influence Of Exogenous Alpha-amylase Supplementation On Development Of Digestive Organs And Enzyme Activities Of Broilers And Its Carry-over Effects

The purpose of this work was to investigate the interrelation between supplementary exogenous a-amylase of microbial origin and the development of broilers' endogenous enzymes. It focused on the major influence of exogenous a-amylase on the synthesis and secretory activity of pancreatic amylase as well as possible carry-over effects. Some referenced information of this field was provided for further exploration of the action mechanism and reasonable application of enzyme inclusion in poultry diets.This study included two parts and the general results were presented as follows:In the first part, an experiment was designed to study the effects of supplementary a-amylase of different levels on the growth, development of digestive organs, endogenous enzyme activities and expression of a-amylase mRNA level within pancreas. Four hundred and forty 1-day-old AA broiler chickens were randomly allocated to four groups of 22 chicks to 10 cages for 5 replicates, and fed a commercial starter diet and the same diets with l,000LU/kg (250mg/kg), 3,000LU/kg (750mg/kg), 9,000LU/kg (2250mg/kg) of a-amylase inclusion up to 21 day of age. Performance of 21-day-old and 42-day-old broilers were also determined. The results showed: (1) Body weight gain was improved in both starter and growth phase, and average feed intake of starter birds was enhanced with amylase inclusion. On day 21 and 42, there was a positive linear relationship (P<0.01) between increasing amylase inclusion and weight gain. Feed conversion ratio (FCR), however, was not affected by amylase supplementation. Optimum enzyme supplementation was 2250 mg/kg for weight gain and 750mg/kg for FCR, respectively. (2) Relative weights of liver, gizzard, and anterior intestine and relative length of anterior intestine tended to decrease (P>0.05), but proventriculus and pancreas tended to increase with increasing levels of supplementary amylase (P>0.05). (3) The activities of amylase, protease (P<0.05), and trypsin (P<0.05) in anterior intestinal contents apparently increased. Lipase was unaffected by amylase supplementation of all levels (P>0.05). Some high-dosage-depression responses were observed with the amylase supplementation of 2250mg/kg. (4) DNA, RNA, protein content...