EFFECTS OF SUPPLEMENTAL ENERGY-SOURCE AND AMOUNT ON FORAGE INTAKE ANDPERFORMANCE BY STEERS AND INTAKE AND DIET DIGESTIBILITY BY SHEEP

Two levels of concentrate supplements containing different types of ca rbohydrates (corn-soybean meal, CSBM; wheat middlings, WM; and soybean hulls, SBH) were evaluated for effects on forage intake and performan ce in growing steers and total diet digestibility in sheep. In Exp. 1, 63 crossbred yearling cattle (298 and 377 kg initial BW for yr 1 and 2, respectively) were given ad libitum access to chopped bermudagrass (Cynodon: dactylon [L.]) hay with no supplementation (CONTROL) or with 25 or 50% of projected total TDN intake from CSBM, WM, br SBH. In Exp . 2, digestibilities of organic matter (OMD) and neutral detergent fib er (NDFD) were determined with sheep fed levels of hay and concentrate s similar to those used in the growth trials. Hay intake was 1.99% of BW for steers fed hay alone and averaged 1.93% of BW in steers fed sup plements at the low level. At the high level of concentrate supplement ation, hay intake was depressed (P < .001) to a similar extent (1.63% of BW) in steers supplemented with CSBM, WM, or SBH. At the low concen trate level, shrunk ADG was similar (.63 kg/d) among supplements, but at the high concentrate level steers fed SBH had higher (P = .06) shru nk ADG (.95 kg/d) than steers fed CSBM (.76 kg/d). Body condition scor e (BCS) increased more (P = .06) for CSBM- and SBH- than for WM-supple mented steers. Total tract OMD was lower (P < .001) in sheep fed WM (5 4.8% for low and 56.9% for high supplementation levels) than in sheep fed CSBM (57.4 and 62.6%) or SBH (57.2 and 62.5%). Total tract NDFD wa s higher (P < .001) for the SBH (58.9% for low and 63.3% for high leve ls) diets than for CSBM (54.6 and 51.0%) or WM (54.6 and 51.8%) diets. Supplements containing highly digestible fiber;(SBH) produced less ne gative associative effects than high-starch supplements (CSBM) when fe d with bermudagrass hay at the high level (.8 to 1% of BW), but no dif ferences were found at the low feeding level (.4 to .5% of BW).