Effects of supplementing prairie hay with corn and soybean meal on intake,digestion, and ruminal measurements by beef steers

Prairie hay supplemented with various amounts of corn and soybean meal was fed to steers in two experiments. Effects of supplementation on hay OM inta ke, digestion, and ruminal fermentation and kinetics were measured. A preli minary study was conducted to attain accurate values for OM intake and dige stibility of prairie hay to be used in ration formulation using the NRC (19 96) level 1 model. Ten steers (284 +/- 9 kg) given ad libitum access to cho pped prairie hay (75% NDF, 6% CP) were supplemented with dry-rolled corn (0 .75% of BW/d) plus soybean meal (0.25% of BW/d). Hay OM intake was 1.85% of BW and hay OM digestibility was 48%. Based on results from the preliminary study, eight ruminally cannulated beef steers (317 +/- 25 kg) received a s equence of eight different supplementation combinations (2 x 4 factorial ar rangement of treatments). These supplements consisted of dry-rolled corn at either 0 or 0.75% of BW (DM basis) daily combined with one of four amounts of added soybean meal to provide between 0 and 1.3 g of degradable intake protein (DIP)/kg of BW. After supplements had been fed for 10 d, feces were collected for 4 d. Intake of hay and total OM increased quadratically (P < 0.01) in response to added DIP with or without supplemental corn. Hay OM d igestibility increased quadratically (P = 0.03) as DIP was added when corn was fed in the supplement. Intake of digestible OM was greater (P < 0.01) w ith than without corn supplementation. Increasing DIP increased (P < 0.01) digestible OM intake regardless of whether corn was fed. Inadequate ruminal ly degraded protein in grain-based supplements decreased forage intake, dig estibility, and energy intake of cattle fed low-quality prairie hay. Provid ing adequate supplemental DIP to meet total diet DIP needs seemed to overco me negative associative effects typically found from supplementing low-qual ity forages with large quantities of low-protein, high-starch feeds.