Combinations of starch and digestible fiber in supplements for steers consuming a low-quality bromegrass hay diet.
Five steers (690 kg) with ruminal and duodenal cannulas were fed 100% bromegrass hay or 60% bromegrass hay:40% concentrate at 90% of their ad libitum DMI. The concentrate consisted of ground corn (GC) and(or) soybean hulls (SBH): 1) 100% SBH; 2) 66% SBH/33% GC; 3) 33% SBH/66% GC; or 4) 100% GC. Increasing level of corn inclusion decreased (linear, P < .01) DM and OM digestion (corrected for microbial DM and OM flow) in the rumen. Neutral detergent fiber digestion decreased in the rumen (quadratic, P = .05) and total tract (linear, P = .06) with increasing level of corn. Ruminal NDF digestion (quadratic, P = .05) and duodenal microbial N flow (quadratic, P < .01) were greatest for 66% SBH/33% GC, whereas total N flow to the duodenum was similar (P > .10) among treatments. Microbial efficiency increased (quadratic, P = .10) as the level of corn inclusion increased. Molar percentage of ruminal acetate decreased (linear, P < .01) with increasing level of corn, whereas molar percentage of butyrate increased (linear, P < .10). Carboxymethylcellulase activity was greatest (quadratic, P = .08) for 66% SBH/33% GC and paralleled NDF digestion in the rumen. Increasing level of corn decreased (linear, P < .07) in situ DM digestibility of SBH after 4, 8, and 12 h of incubation.
Grigsby
K N
KN
Department of Animal Sciences, University of Missouri, Columbia 65211.
Kerley
M S
MS
Paterson
J A
JA
Weigel
J C
JC
D000641:Ammonia / Q000032:analysis; D000821:Animal Feed; D000818:Animals; D001419:Bacteria / Q000378:metabolism; D002417:Cattle / Q000502:physiology*; D002480:Cellulase; D004043:Dietary Fiber / Q000008:administration & dosage*; D004063:Digestion; D005232:Fatty Acids, Volatile / Q000032:analysis; D005285:Fermentation; D005527:Food, Fortified; D005772:Gastrointestinal Transit; D006026:Glycoside Hydrolases / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D006109:Poaceae; D012417:Rumen / Q000737:chemistry / Q000201:enzymology / Q000382:microbiology / Q000502:physiology*; D013213:Starch / Q000008:administration & dosage*
D004043:Dietary Fiber; D005232:Fatty Acids, Volatile; D000641:Ammonia; D013213:Starch; D006026:Glycoside Hydrolases; D002480:Cellulase; C019826:carboxymethylcellulase; D009584:Nitrogen