Study For Effects Of Supplementing Low-protein Diets With Sodium Dichloroacetate On Nitrogen Balance, Nutrient Metabolism And Gastrointestinal Microbial Community Of Dazu Black Goats

Reducing dietary crude protein level is an important way to reduce nitrogen emissions and save protein feed resources.Sodium dichloroacetate?DCA-Na?is a small molecule compound,which can activate pyruvate dehydrogenase by inhibiting the dephosphorylation of pyruvate dehydrogenase kinase,increase the flow of pyruvate into mitochondria,and produce a large amount of acetyl CoA,which initiates the tricarboxylic acid cycle and promotes the oxidative phosphorylation of glucose.This experiment was conducted to study the effects of low-protein diets supplemented with DCA-Na on nitrogen balance,nutrient metabolism,and microbiota in the digestive tract of Dazu black goats,and to provide the scientific basis for the development of ruminant nitrogen emission reduction technology.Experiment 1:nitrogen balance test.Six castrated Dazu black goats with good health and body weight of 24.22±0.40 kg were fed in a single cage using a repetitive3×3 Latin square design.Three groups of experimental diets were:experimental diet 1?13.2%CP,control group?;experimental diet 2?11.6%CP+500 mg/kg,DCA-Na?;experimental diet 3?9.9%CP+500 mg/kg,DCA-Na?.Each experiment lasted for 10days,and the sampling period was the last 4 days.Fecal and urine samples were collected for protein content determination to calculate nitrogen balance and apparent digestibility.The results showed that low-protein diet supplemented with DCA-Na significantly reduced urine nitrogen and fecal nitrogen emissions of Dazu black goats?P<0.05?,increased the biological value of nitrogen?P<0.05?,but had no significant effect on nitrogen deposition?P>0.05?;low-protein diet supplemented with DCA-Na significantly increased the apparent digestibility of CF,NDF,and ADF of Dazu black goats?P<0.05?.Experiment 2:digestion test.Six castrated Dazu black goats with good health and body weight of 25.45±0.28 kg were selected to install permanent rumen fistula,proximal duodenal fistula,and distal ileal fistula,which were to be used in the experiment after resuming normal feeding.A repetitive 3×3 Latin square test design was used.The three groups of experimental diets were consistent with the experimental1.Each experiment lasted for 12 days,and the sampling time was the last 3 days.Rumen contents,duodenum,and ileum chyme were collected for determination of rumen parameters,small intestinal amino acid flux and absorption rate.The results showed that low-protein diet supplemented with DCA-Na significantly decreased NH₃-N concentration in rumen fluid of Dazu black goats?P<0.05?,significantly increased the concentration of propionic acid and butyric acid in rumen fluid?P<0.05?,and significantly decreased the ratio of acetic acid to propionic acid?P<0.05?;low-protein diet supplemented with DCA-Na had no significant effect on the pH value of duodenal and ileal contents of Dazu black goats?P>0.05?.DCA-Na supplementation in low-protein diet significantly decreased the flow of threonine and essential amino acids in ileum?P<0.05?,but had no significant effect on the flow of amino acids in duodenum?P>0.05?;DCA-Na supplementation in the low-protein diet significantly increased the absorption of CP,CF,NDF and ADF in small intestine?P<0.05?.Experiment 3:microbiota analysis.Six castrated Dazu black goats weighing24.48±0.29 kg and in good health were selected as experimental animals.The experimental design is consistent with experiment 2.Permanent rumen fistula,proximal duodenal fistula,and terminal ileal fistula were installed for testing after normal feeding.The three groups of experimental diets were consistent with the experimental 1.Each experimental period was 14 days.Rumen and ileum contents were collected for microflora analysis.The results showed that the low-protein diet supplemented with DCA-Na significantly increased the OTU number of rumen microorganisms in Dazu black goats?P<0.05?,but had no significant effect on Alpha diversity index,phylum level and genus level?P>0.05?;low-protein diet supplemented with DCA-Na had no significant effect on Alpha diversity index of ileum microorganisms in Dazu black goats?P>0.05?.Among them,11.6%CP+500 mg/kg DCA-Na group had significantly higher content of Firmicutes than the other two experimental groups?P<0.05?,and 9.9%CP+500 mg/kg DCA-Na group had significantly higher abundance of Bacteroidetes,Fusobacteria,Fusobacterium,Porphyromonas than the other two experimental groups?P<0.05?.The results showed that adding DCA-Na to the low-protein diet could significantly reduce nitrogen emissions and improve the protein utilization efficiency of Dazu black goats.