Study About The Effects Of Dietary Protein Levels On The Microbe Nitrogen Metabolism And Enzymatic Activity Of Piglets

The objective of this study was to determine the effect of dietary crude protein (CP) levels on nitrogen metabolism and enzyme activity of the intestinal microbes in piglets. A total of 54 Duroc×Landrace×Yorkshire 28-d weaned piglets (5.55±0.49 kg) were randomly allocated to 3 treatments with 18 barrows per group.Piglets in 3 treatments fed a maize-soybean meal diet containing 20% CP,17% CP and 14% CP, respectively. The experiment lasted 7 d adaptation period and 45 d test period. Six piglets were selected from each group to be collected feces and were slaughtered to be collected intestinal digesta on d 10, d 25 and d 45, respectively. To achieve this purpose, this study had carried on the following several aspects research:(1) the effect of dietary CP levels on feces excretion and apparent digestibility, total fecal amino acid excretion, the apparent digestibility of amino acids, fecal excretion and apparent digestibility and fecal microbial amino acid excretion in piglet; (2) the effect of dietary CP levels on the composition of the ileal and faecal microbial amino acids in piglets; (3) the effect of dietary CP levels on intestinal microbial extracellular enzyme activity in piglets; (4) the effect of dietary CP levels on intestinal microbial decarboxylase enzyme activity in piglets.The results showed that:(1) the interaction effects of feeding time and dietary CP levels were reflected in the apparent digestibility of CP and amino acid in the diet (P<0.01). With the increase of age, the apparent digestibility of crude protein/amino acid were increased significantly (P<0.01). With the increase of CP levels, the excretion of N were decreased significantly (P<0.01), but the amino acid of microbial in ileum and fecal were increased significantly (P<0.01). The proportion of amino acid of microbial in fecal was about 1～5%. After deducted amino acid of microbial, the excretion and apparent digestibility of total amino acid were not influenced by dietary protein levels, but the essential amino acid (EAA)/non-essential amino acid (NEAA) was influenced by dietary CP levels. (2) The interaction effects of feeding time and dietary CP levels were reflected on the amino acid composition of the ileum and fecal in piglets (P<0.01). The effect of dietary CP levels on the rule of composition of amino acid in the piglets was found. The Asp, Ala, Glu and Leu of microbial bacteria in intestinal were influenced by dietary CP levels. The amino acid composition of microbial bacteria in ileum was similar to rectum. The proportion of His, Lyr, Met, Cys and Ser were lower than average, but the proportion of Phe, Leu, Pro, Ala, Glu and Asp were higher than average. With the increase of age, the amino acid of microbial bacteria was significantly increased. With the increase of protein levels, the EAA/NEAA of microbial bacteria in the ileum and fecal was decreased significantly. (3) The effects of dietary CP levels on the enzyme activity of composition of amino acid in microbial bacteria. Microbial enzyme activity of intestinal in piglets had a bowel-specific, dietary protein levels had influenced significantly on Nitrate Reductase, Adenosine Deminase, Glutamine Synthetase, Urease, Glutamic-pyruvic Transaminasa and protease of microbial in intestinal (P<0.05), and regulated N metabolism of microbial in intestinal, it would cause the variation of amino acid composition of microbial. (4) It was clarified that the dietary protein levels had influenced enzyme activity of biogenic amines. The dietary CP levels had significantly influenced on decarboxylase activity of Met, His, Lys, Arg, Gly, Tyr, Try and Glu of microbial in intestinal (P<0.05), it would cause the variation of biogenic amines concentrations. With the elevation of decarboxylase activity of microbial in intestinal, biogenic amines concentrations would be rosed, increased digestibility illusion. It was one of the reasons for differences in the intestinal microbial degradation of amino acid and also an important reason for low utilization of protein in piglets.In summary, the thesis reveals some scientific problems about followed by the intestinal microbial, focused on the effects of dietary protein levels on crude protein、 amino acid apparent digestibility in the piglets and the amino acid composition of the microbial bacteria, intracellular enzyme activity, decarboxylase activity of microbial in intestinal. It showed that, it was variation rules of N, CP, amino acid excretion and digestibility in feces and microbial, the variation law of amino acid composition of microbial and the enzyme mechanism of composition of amino acid in microbial bacteria and the production of biogenic amines under the different protein levels and feeding time. It would provide a theoretical basis about how to change the gastrointestinal microbial nitrogen nutrient supplied model and how to change the gastrointestinal digestion and metabolism of nitrogen nutrient supplied model.