Synchronization of Carbohydrate and Protein Metabolism by Ruminal Microbes in a Continuous Culture

[摘要] A major factor in maximizing microbial protein synthesis is the availability of energy and protein in the diet.Our objective was to determine the effect of fermentable carbohydrate and protein on microbial fermentation.Diets were formulated using three ingredients, soybean meal (SBM), ground corn (GC) and soybean hulls (SBH).Corn and SBH were used in ratios of 60:20, 40:40 or 20:60, respectively to prepare high, medium or low non-fibrous carbohydrate (NFC) diets.Soybean meal was included either unextruded (control) or extruded at low, medium or high temperature.Degradability of the N fractions in the control, low, medium and high soybean meal were 97, 80, 80 and 60%, respectively.Diets were arranged as a 3 x 4 factorial (3 levels of corn/soybean hulls and 4 levels of protein) and analyzed as a completely randomized block design.There were no statistically significant interactions seen between NFC and protein sources. Total volatile fatty acids were affected (P<0.01) by the NFC with 78.5, 63.2 and 71.5 mM with increasing NFC levels.The NFC level affected the acetate and butyrate whereas the protein source had an effect on the propionate.Molar ratios of acetate, propionate and butyrate averaged 60.1, 31.0 and 6.79, respectively.Varying the level of fermentable carbohydrate had a negative linear affect on ruminal pH (P<0.01).Extrusion did not alter pH greatly P>0.67).Higher extrusion temperatures altered ammonia concentrations when compared to control or low extrusion.In the low NFC diets, the medium and high extrusion increased (P<0.10) ammonia concentration (29.8 and 32.6 mg/dl, respectively) when compared with control and the low (18.9 and 23.4 mg/dl, respectively).Methane concentration averaged 308 nmoles/ml and was affected by both the NFC treatment and protein source.The high and medium NFC diets increased (P<0.01) bacterial nitrogen percentage (9.0 and 9.5%, respectively) compared to the low NFC diet (8.7%).Data suggest that the fermentability of the structural carbohydrates in SBH was similar to the high starch corn diets.Furthermore, large differences in protein degradability did not seem to have a major impact on microbial fermentation.

[发布机构] University:North Carolina State University

[效力级别] SCFA

[关键词] synchronization;SCFA;rumen fluid;pectin;extrusion