Microbiologic Mechanism Of High Grain Diet Alter Ruminal Metabolism In Goat

High-grain diet would induced the ruminants suffering from subacute ruminal acidosis. This nutritional and metabolic disease could endanger the health and milk quality of dairy cows seriously, and restricts our ruminant farming industry greatly. The objective of the present study was to determine the effect of high-grain diet on rumen fermentation characteristics, the evolution of rumen microbial flora and the composition of rumen metabolites, and this study was carried out as following:1 Effect of high-grain diet on rumen fermentation and the inflammation indices in goatsThis study was conducted to investigate the effects of feeding increasing proportions of corn grain on concentration of lipopolysaccharide (LPS) in the rumen fluid and the subsequent alterations in immune responses as reflected by plasma concentrations of serum amyloid A (SAA) and haptoglobin (Hp) in goats. Nine goats with permanent rumen cannula were assigned to three diets (0%,25%, and 50% corn grain) in a 3 x3 Latin square experimental design. The results showed that as the proportion of dietary corn increased, the ruminal pH decreased (P< 0.001), and the concentrations of propionate (P< 0.001), butyrate (P< 0.001), lactic acid (P=0.013) and total volatile fatty acid (P=0.031) elevated, the ruminal LPS level increased (P< 0.001). As the proportion of dietary corn increased, the concentration of SAA increased (P=0.013). LPS was detectable in blood of the individual goats fed 25% and 50% corn. Collectively, these results indicated that feeding goats high proportions (50%) of corn grain decreased the ruminal pH, increased LPS in the rumen fluid and tended to stimulate an inflammatory response.2 Effect of high-grain diet on the changes in the rumen microbial flora and the composition of rumen metabolites when fed with high grain diet in goatsFeeding ruminants high-grain diets increases the incidence of rumen and systemic metabolic disorders; however, the precise mechanism(s) of how grain feeding results in disease is not well understood. In an effort to understand how high concentrate diet alters the rumen environment and potentially leads to certain metabolic disorders, a combination of the bar-coded 454-pyrosequencing strategy and the metabolomics technique was applied to investigate the effects of an increase in dietary grain (0%,25% and 50% maize grain) on changes in ruminal microbiota and their metabolites using goats as a ruminant model. The results suggested that was a significant difference between the microbiota of the goats fed the 50% grain diet and the microbiota of the goats fed the 0% grain diet. The former was characterised by an increased abundance of the genera Butyrivibrio, Acetitomaculum, Mogibacterium and unclassified Anaerolineaceae, as well as reduced microbial diversity and a lower percentage of Prevotella, Papillibacter, Thalassospira, unclassified Bacteroidales and unclassified Prevotellaceae, compared with the goats fed the 0% grain diet. These findings indicate that a high-grain diet induces compositional alterations in the ruminal microbiota that lead to a less stable microbial ecosystem in the rumen. The metabolomics analysis revealed a clear difference in the metabolic composition of the ruminal fluid between the control and the grain-fed group, with the latter showing a marked increase in the levels of several toxic, inflammatory and unnatural compounds, including butyrate, endotoxin and phenylacetate. These results indicate that higher levels of butyrate, amine and endotoxins, may contribute to the chronic inflammation that is usually observed in animals fed a high-grain diet. Correlation analysis revealed that the microbial populations or metabolites affected by the high-grain feeding were significantly associated with five or more ruminal compounds or microbial populations. Taken together, this study shows that the use of that a combination of microbiome and metabolomic approaches permits a far more detailed understanding of metabolic and microbial causes and effects. These results may improve our understanding of the effects of high-grain diet on the microbiota and metabiome of the rumen and the overall health of ruminants.3 Effect of high-grain diet on transference of LPS and biogenic amine from rumen to peripheral circulation in goatsThis study was conducted to investigate the effects of feeding increasing proportions of corn grain on concentration of lipopolysaccharide (LPS) and biogenic amine in the rumen fluid, rumen vein blood and jugular vein blood, and the metabolites in peripheral circulation composition. Nine goats with permanent rumen cannula were assigned to three diets (0%,25%, and 50% corn grain) in a randomized block experimental design,28 d after slaughter sampling. The results showed that, as the proportion of dietary corn increased, the ruminal pH decreased (P< 0.001), and the concentrations of LPS (P< 0.001), histamine (P <0.001), methylamine (P=0.010), putrescine (P< 0.001), tyramine (P< 0.001) and tryptamine (P= 0.001) elevated, the concentrations of LPS (P= 0.024), histamine (P< 0.001), methylamine (P< 0.001), putrescine (P<0.001), tyramine (P< 0.001) and tryptamine (P< 0.001) in rumen vein and jugular vein increased. Collectively, these results indicated that feeding goats high proportions (50%) of corn grain decreased the ruminal pH, increased LPS and biogenic amine in the rumen fluid, rumen vein and peripheral circulation, and tended to stimulate an inflammatory response.4 Effect of increasing buffer capacity in medium on the changes in the levels of LPS and bioamine in vitro fermentation using high grain as substratesThe preset study was to determine the effect of the the buffer capacity (control (A group) and high levels of sodium bicarbonate (B group) on rumen microbiota evolution, LPS and bio-amines concentrations when high proportion grain (50% grain) was used as the substrat in in vitro fermentation. Rumen contents were collected from three cattles fed lucerne hay ad libitum and supplemented with 2.5 kg concentrate/d. The results showed that, after 24 h incubtion, the pH value in B group was greater than 6, and the pH value in A group was about 5.5. The acetic acid, propionic acid, isobutyric acid, isovaleric acid, and valeric acid concentrations were significantly higher in B group than that in A group (P< 0.001), and the concentration of butyrate in B group was lower than A group (P< 0.001). As compared with the control, the LPS concentration in B group were higher (P< 0.001), and the concentration of lactic acid was lower in B group (P< 0.001). The biogenic amines (methylamine, tryptamine, tyramine, histamine and putrescine) concentrations were lower in B group compared with A group (P< 0.001). When compared with the control, the bacterial diversity indext (Chao1 and shannon index) were higher (P< 0.001). The proportion of Firmicutes was higher in A group (6.6 to 5.3), and the B group was higher (6.8 to 6.0) with a larger proportion of Bacteroidetes. Compared with the control, high levels of sodium bicarbonate addition decreased the relative abundance of Streptococcus, Butyrivibrio, and icnreased the proportions of Ruminococcus, Succinicvibrio, Treponema, Prevotella and Bacteroides. Colletively, the increase in the relative abundance of Proteobacteria may result in the dramatively increase in the LPS in B group, and the higher levels of biogenic amine in A group may be resulted from the high proportion of streptococci in A group. These findings revealed that an increase in the buffer capacity in media could increase the pH and TVFA concentration. However, in any case, high concentrate feeding will result in an accumulation of LPS and the increase the risk for host health.