Impact of carbohydrate and protein levels on bacterial metabolism in continuous culture.
Diets formulated with three levels of nonstructural carbohydrate (54, 37, and 25% of DM), with various concentrations of degradable intake protein ranging from 19 to 4% of DM, were fermented in continuous cultures to ascertain the effects of ratio of nonstructural carbohydrate to degradable intake protein on bacterial metabolism. Fermenters were maintained at a dilution rate of 12%/h with a solids retention time of 24 h. Regardless of degradable intake protein level, bacterial efficiency (g of bacterial N/kg of DM digested) and VFA production (mM/d) were lower for diets with 25% nonstructural carbohydrate compared with the 37 and 54% nonstructural carbohydrate diets. In response to widening nonstructural carbohydrate:degradable intake protein ratios, bacterial efficiencies at all nonstructural carbohydrate levels declined quadratically from 34.2 to 10.3 with the lowest efficiencies on the 25% nonstructural carbohydrate diets. Bacterial protein production, DM digestion, NDF digestion, and VFA production (mM/d) increased linearly in response to dietary protein. The enhanced NDF and DM digestion, VFA production, and bacterial efficiencies observed with the narrower ratios of nonstructural carbohydrate:degradable intake protein support the theory that level of both degradable intake protein and nonstructural carbohydrate should be considered in order to enhance ruminal digestion and bacterial N production.
Stokes
S R
SR
Department of Animal Science, Food and Nutrition, West Virginia University, Morgantown 26506.
Hoover
W H
WH
Miller
T K
TK
Manski
R P
RP
D000821:Animal Feed; D000818:Animals; D001419:Bacteria / Q000378:metabolism*; D002417:Cattle; D003960:Diaminopimelic Acid / Q000032:analysis; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004043:Dietary Fiber / Q000378:metabolism; D004044:Dietary Proteins / Q000378:metabolism*; D004063:Digestion; D005232:Fatty Acids, Volatile / Q000096:biosynthesis; D005260:Female; D009584:Nitrogen / Q000378:metabolism; D012417:Rumen / Q000378:metabolism / Q000382:microbiology* / Q000502:physiology
D004040:Dietary Carbohydrates; D004043:Dietary Fiber; D004044:Dietary Proteins; D005232:Fatty Acids, Volatile; D003960:Diaminopimelic Acid; D009584:Nitrogen