Utilization of Supplemental NPN and Energy Sources by Beef Steers Consuming Low-Protein Hays

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Abstract
Three experiments were conducted to evaluate the effect of readily available supplemental energy sources on utilization of non-protein nitrogen (NPN) by steers fed low protein hay. In Experiment I, urea and biuret as NPN supplements to fescue and broomsedge hay (6% crude protein) gave similar nutrient digestibility and nitrogen (N) utilization. Intake of hay was low for all rations. In Experiment I, addition of dry (corn meal) or liquid (molasses) supplement to the biuret increased digestibility of dry matter and energy, but had no significant (P<.05) effect on N utilization. In Experiments II and III, rations containing no supplemental N or biuret were factored with three supplemental energy sources-control (no supplemental energy), corn and citrus pulp, and molasses. Inclusion of biuret significantly (P<.05) increased Pangola digitgrass hay intake after the first week of adaptation in Experiment II. During the metabolism trials (Experiment III) animals receiving biuret were in positive N balance (12 to 17 g/day) where those receiving no supplemental N were in negative N balance. Addition of supplemental energy increased N retention numerically but not statistically (P>05). Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.