EFFECTS OF PROTEIN-CONCENTRATION AND PROTEIN-SOURCE ON PERFORMANCE OFNEWLY ARRIVED FEEDLOT STEERS

In Trial 1, 240 crossbred steers (initial BW 243 +/- 8 kg) were used i n a 2 x 4 factorial experiment to determine the effects of receiving d iet CP concentration (12, 14, 16, or 18%) and source (spray-dried bloo d meal [SDBM] vs soybean meal [SBM]) on steer performance. There were linear (P < .01) increases in ADG and feed efficiency during wk 1. For the entire trial, there was an increase (P < .01) in feed efficiency with increasing CP concentration and diets containing SDBM compared wi th those containing SBM. In Trial 2, 240 crossbred steers (initial BW 246 +/- 14 kg) were used in a completely randomized design experiment to determine the effects of receiving diet CP concentration (11, 14, 1 7, 20, 23, or 26%) on steer performance. Average daily gain and feed e fficiency increased (P < .01) with increasing CP concentration during wk 1. There were quadratic (P < .01) responses to CP concentration for final weight, ADG, and feed efficiency. In Trial 3, 216 steers (initi al BW 238 +/- 1 kg) were used to determine the effects of receiving di et protein sources on steer performance. The control diet used SEM as the supplemental CP source and was formulated to contain 12.5% CP. The other five protein sources were corn gluten meal (CGM), ring-dried bl ood meal (RDBM), SDBM, fish meal(FM), and SBM. For these five CP sourc es, diets were formulated to contain 23% CP during wk 1, 17% CP during wk 2, and 12.5% CP during wk 3 anti wk 4. During wk 1, control steers had the lowest ADG (P < .07) and feed efficiency (P < .01) whereas st eers fed RDBM and SDBM had the highest (P < .01) feed efficiency. Incr eased CP concentrations are needed early in the receiving period, when DMI is low.