The influence of restricted feeding on site and extent of digestion and flow nitrogenous compounds to the duodenum in steers.
Murphy T.A. | Loerch S.C. | Dehority B.A.
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 < 0.06) ruminal pH and ammonia concentrations, decreased (P < 0.05) 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 < 0.06) 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.
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