title: The influence of restricted feeding on site and extent of digestion and flow of nitrogenous compounds to the duodenum in steers.
abstract: The effects of restricted feeding on site and extent of digestion, flow of N-containing compounds to the duodenum, and ruminal metabolism were determined. In Trial 1, corn silage-based diets were fed at one of three intakes to three ruminally and duodenally fistulated steers (420 +/- 4.4 kg BW) in a repeated 3 x 3 Latin square experiment. Feeding levels were 100% of ad libitum intake, 90% of ad libitum intake, and 80% of ad libitum intake. Site of digestion was not affected by restricted feeding; however, extent of DM, NDF, and apparent N digestion were increased (P < .03) 2.8, 4.1, and 6.2 percentage units for each 1-kg restriction in DM intake. Restricted feeding increased (P < .06) ruminal pH and ammonia concentrations, decreased (P < .05) ruminal liquid dilution rate, and had no major effects on bacterial concentrations. In Trial 2, all-concentrate diets based on whole shelled corn were fed at 100, 90, or 80% of ad libitum intake to six ruminally and duodenally fistulated steers (440 +/- 4.1 kg BW) in a replicated 3 x 3 Latin square experiment. Restricted feeding increased (P < .06) apparent ruminal DM digestion; however, true ruminal OM digestibility was not affected. Extent of apparent N digestion increased 3.0 percentage units for each 1-kg restriction in DMI. Ruminal pH was not affected by restricted feeding; however, ruminal ammonia concentrations increased (P < .06) and ruminal liquid dilution rate decreased (P < .04) with restricted feeding. In both Trials, total N flow to the duodenum was approximately 100% of N intake for the 80% of ad libitum intake. Flow of N exceeded N intake in a linear (P < .01) manner as DMI increased. Decreases in duodenal N flow when intake was restricted resulted from decreases (P < .01) in bacterial N flowing to the duodenum, and also in decreases (P < .01) in non-ammonia, non-bacterial N flow when whole shelled corn-based diets were fed. We concluded that restrictions in digestible energy intake are less than the DM restriction when corn silage-based diets are fed but are equal to the DM restriction when whole shelled corn-based diets are fed. Also, restricted feeding strategies reduce the flow of N to the duodenum from both bacterial and feed origins.
authors.affiliation: Department of Animal Science, Ohio Agricultural Research and Development Center, Ohio State University, Wooster 44691.
authors.forename: T A
authors.initials: TA
authors.lastname: Murphy
authors.forename: S C
authors.initials: SC
authors.lastname: Loerch
authors.forename: B A
authors.initials: BA
authors.lastname: Dehority
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism; D004043:Dietary Fiber / Q000008:administration & dosage; D004063:Digestion; D004435:Eating / Q000502:physiology*; D005508:Food Deprivation / Q000502:physiology; D005772:Gastrointestinal Transit; D006863:Hydrogen-Ion Concentration; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D012417:Rumen / Q000378:metabolism*; D003313:Zea mays
chemical_list: D004040:Dietary Carbohydrates; D004043:Dietary Fiber; D009584:Nitrogen