| Five experiments were conducted to investigate the peptide processing and the effect of peptide on the growth performance of broilers.Experiment 1 the processing of peptide in labThe experiment was carried out in vitro to evaluate the effect of temperature, enzyme dosage and reaction time on the reaction of enzymes of pancreas hydrolyze casein. The trial was a 3+3+3 factorial arrangement including three temperature level (37 C, 45 C, 50 C) , three ratio of enzymes to casein ( 1 : 25, 1 : 30, 1 : 35) and three reaction time (4,5, 6 hours). In order to keep the highest activity of enzyme, 10% NaOH was dripped into reaction solution in the course of reaction and maintained the pH of solution at 8.0. At the end of reaction, the enzymes of pancreas were denatured by heating solution to 80 C for half an hour. The content of amidogen nitrogen in solution was determined and the hydrolysis degree of casein was calculated. The results showed that the hydrolying reaction was affected significantly by temperature, enzyme dose and reaction time. The hydrolysis degree increased with increasing of temperature, enzyme dose and reaction time. The suitable processing condition was the temperature of 50 C, the ratio of enzymes to casein of 1 : 30 and the reaction time of 6 hours.Experiment 2 the mass processing of peptide and its quality analyze methodThe experiment was conducted to study the processing under the situation of temperature at 50 C, enzyme dosage at 1:30 and the reaction time of 6 hours. A set of checking method was established to analyze the component and to test the quality of peptide product. The indexes tested included moisture, average chain length of peptide, the percentages of free amino acid, oligopeptides and multipeptides of peptide product. The results showed the processing that including confecting the casein solution, hydrolyzing reaction, filtrating treatment, salt-removing treatment, vacuuming condensation, spraying and drying could be used to produce peptide. The percentage of moisture was 5.634%. The average chain length of peptide was 3.78. The percentage of moisture was 5.634%. The percentages of oligopeptides and multipeptides that molecular weight waslower or higher than 1000Da respectively of dry matter were 90.590% and 4.090%. The peptide product that produced by this process meets the standard and could be used as material in theory study or practice.Experiment 3 Study of the absorption rate of peptide in broiler chicksThe experiment was conducted with male avian broiler chicks to determine the absorption rate of peptide comparing with that of amino acids and casein. One hundred three-week-old chicks were randomly allotted into 4 different treatments consisted of five replicates of 5 birds each. After 32 hours fasting the birds received four different diets with the casein, peptide and amino acid as protein resource respectively and 0.5% Cr2O3 as indicator. Under narcotism in the end of experiment, the chicks were anatomized and the chyme was collected from the end of ileum. The content of protein, amino acid and Cr2O3 in chyme was analyzed. The absorption rate of casein, peptide and amino acid were calculated. The results showed that the absorption rate of amino acid was significantly higher than those of peptide and casein by 5.10% and 5.27% (P<0.01). There was not significantly different between the absorption rates of peptide and casein (P>0.05). The absorption rates of most amino acids in amino acid treatment, such as aspartic acid, threonine, serine, glutamic acid, glycine, alanine, valine, methionine, isoleucine, lysine, histidine, proline, tryptophan, were significantly bigger than those of amino acids in peptide and casein treatments (P<0.05 or P<0.01). It means that the decrease of absorption rate of peptide and casein was caused by absorption rate decrease of most amino acids. Though the absorption rate of peptide and casein decreased, the absorption rate differences between amino acid treatment and peptide (of casein) treatment were variable. The absorption...
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