Effects Of Small Peptide On In Vitro Rumen Fermentation Characteristics Of Nanjiang Brown Goat Under The Condition Of Different Nitrogen-sulfur Ratio Of Urea Diet

In this study, four artificial rumen simulation experiments were taken to research the effects that the di-peptide and the tri-peptide of different amino acid composition, nitrogen-sulfur ratios and different combinations of nitrogen-sulfur ratios, the di-peptide, the tri-peptide and the urea took on the rumen fermentation characteristics of Nanjiang Brown Goats (NBG). The first step was to screen out the di-peptide and the tri-peptide which has the best effect on the rumen fermentation and the appropriate nitrogen-sulfur ratios through the first three experiments. The second step was to comprehensively considerate the effects that the nitrogen-sulfur proportion, the di-peptide, the tri-peptide, and the urea took on rumen fermentation based on the previous three experiments. Finally, through the research of the above several experiments, we found out the most favorable nitrogen-sulfur proportion, types of di-peptide and tri-peptide and the best combination of nitrogen-sulfur proportion, dipeptide, tri-peptide and the urea on rumen fermentation.Experiment one:The effects that the di-peptide of differed amino acid composition taking on the rumen fermentation characteristics of NBGThis experiment aimed to investigate the effect that adding the di-peptides of different amino acid composition into daily diet took on ruminal fermentation characteristics. Making four healthy NBG fitted with permanent rumen fistula as the donor of rumen fluid, using two-factor experimental design, through test in vitro culture, to study the effects that the di-peptide (Leu-Trp, Val-Met, Tyr-Ala, Phe-Val) of four different amino acids composition and its four different addition levels (0%,0.5%,1%,2%) will take on the pH of rumen medium, the concentration of ammonia nitrogen (NH3-N), the content of volatile fatty acids (VFA) as well as the production of microbial protein (MCP). The results showed that pH, NH3-N concentration and the ratio of acetic acid to propionic acid would decrease while the VFA content and MCP production would increase with the rise of the di-peptide adding level (P<0.05) during the entire fermentation process. Comprehensively studying the average effect at each time point, we found that in Val-Met treatment group, the medium pH, NH3-N concentration and the ratio of acetic acid to propionic acid was significantly lower than other di-peptide treatment groups (P<0.05); comparing with the other three peptides, Val-Met di-peptide significantly increased the TVFA content and MCP production in the medium(.P<0.05). Therefore, adding the di-peptides into daily diet was useful to the rumen fermentation and the effect related to adding level and type, under the conditions of this study, the effect of the Val-Met di-peptide was the best.Experiment two:The effects that the tri-peptide of different amino acid composition taking on rumen fermentation characteristics of NBGThis experiment aimed to study the effects that adding the tri-peptide of different amino acid composition into daily diet takes on rumen fermentation characteristics. Using two-factor experimental design, with vitro culture test, to study the effects that the tri-peptide of four different amino acid composition peptide (Lys-Lys-Lys、Gly-Gly-His、Met-Ala-Se、Val-Tyr-Val) and its four different addition levels (0%,0.5%1%,2%) take on rumen medium pH, the concentration of ammonia nitrogen (NH3-N), the content of volatile fatty acids (VFA) and yields of microbial protein (MCP). The results showed that the different adding level of the tri-peptide had a similar effect with the di-peptide on different fermentation parameters of rumen. Within8hours before fermentation, the NH3-N concentration in the culture medium in the adding groups of Val-Tyr-Val and Met-Ala-Ser was significantly lower than that of Gly-Gly-His adding group (P<0.05). Within the first4h of fermentation, the ratios of acetic acid to propionic acid of the Val-Tyr-Val adding group was significantly lower than that of other three peptides adding groups(P<0.05). Within the fourth hour, the eighth hour and the twelfth hour, TVFA content in the culture medium in the Val-Tyr-Val adding group was significantly higher than the adding groups of Lys-Lys-Lys and Gly-Gly-His(P<0.05), compared with Met-Ala-Ser, the difference was not significant (P>0.05). The results of the effects of MCP yield showed that the effect of Val-Tyr-Val tri-peptide was the best, followed by Met-Ala-Ser, Lys-Lys-Lys and Gly-Gly-His. Comprehensively considering the results of impacts of various fermentation parameters, the Val-Tyr-Val tri-peptide was most favorable to the rumen fermentation, followed by Met-Ala-Ser tri-peptide.Experiment three:The effects that different nitrogen-sulfur ratios in daily diet taking on characteristics of rumen vitro fermentation of NBGThis experiment aimed to explore the effects that different nitrogen-sulfur ratios in daily diet taking on characteristics of rumen vitro fermentation. Using single-factor experiment design, through vitro culture experiment, to study the effects that different nitrogen-sulfur ratios(10.5:1,9:1,7.5:1and6:1respectively) in daily diet take on rumen pH, ratio of dry matter (DM) degradability, concentration of ammonia nitrogen (NH3-N), content of volatile fatty acids (VFA) and yield of microbial protein (MCP). The results showed that different nitrogen-sulfur ratios in diet did not affect pH in the medium (P>0.05). DM degradability ratio in7.5:1group was significantly higher than that in the other treatment groups at the time of the4th hour,8th hour, and12th hour(P<0.05). The NH3-N concentrations in7.5:1and9:1groups were significantly lower (P<0.05) than that in the10.5:1group within8hours before culture. To reduce the nitrogen-sulfur ratio would significantly reduce the ratios of acetic acid and propionic acid (P<0.05). The total amount of VFA, protozoa protein, bacterial protein and MCP, in7.5:1group was significantly higher than that in the other groups (P<0.05).In conclusion, there existed a suitable nitrogen-sulfur ratio for the growth of rumen microbial, under this experiment condition, the optimum nitrogen-sulfur ratios was7.5:1.Experiment four:Effects of small peptide on in vitro rumen fermentation characteristics of NBG under the condition of different nitrogen-sulfur ratio of urea dietThis test aimed to explore the best combination of di-peptide (Val-Met), tri-peptide (Val-Tyr-Val), nitrogen-sulfur ratio and urea which was favorable to rumen fermentation. Using orthogonal experimental design L9(34), to study the effects that different combinations of nitrogen-sulfur ratio, di-peptide, tri-peptide and urea take on ruminal fermentation characteristics and rumen microbial flora. The results showed that the effects of the combination whose nitrogen-sulfur ratio was7.5:1, di-peptide adding level was0.5%, tri-peptide adding level was1%and urea adding level was1%took on medium protozoan protein, the bacterial protein and total microbial protein yield was the best. In addition, the combination whose nitrogen-sulfur ratio was9:1, di-peptide adding level was0.5%, tri-peptide adding level was0.5%and urea adding level was1%would have the highest yield on acetic, propionic, butyric and total VFA, the ratio of acetic acid and propionic acid was the lowest.The results of relative expression amount of a variety of microorganisms showed that the combination of nitrogen-sulfur ratio(7.5:1),0.5%of di-peptide,1%of tri-peptide and2%of urea was most favorable to increase the expression amount of Megasphaera elsdenil and protozoa; while the combination of nitrogen-sulfur ratio(9:1),0.5%of di-peptide,0%of tri-peptide and0%of urea was most favorable to the growth of Selenomonas ruminantium. The best combination of growing conditions of Streptococcus bovis was nitrogen-sulfur ratio7.5:1,0%of the di-peptide,0%of the tri-peptide, and2%of urea. The best combination conditions of Butyrivibrio fibrisolvens was nitrogen-sulfur ratio6:1,0.5%of the di-peptide,0%of the tri-peptide, and2%of urea; while the combination of nitrogen-sulfur ratio9:1,0%of the di-peptide,0.5%of the tri-peptide, and0%of urea and the combination of nitrogen-sulfur ratio9:1,0%of the di-peptide,0%of the tri-peptide, and2%of urea was respectively the best growing condition of Prevotella ruminicola and Ruminobacter amylophilus. Therefore, different microorganism had different combination of the best growing condition, comprehensively considering each rumen fermentation parameter, we obtained the most favorable combination condition to rumen fermentation was the combination of nitrogen-sulfur ratio7.5:1,0.5%of the di-peptide,1%of the tri-peptide, and1%of urea.