Results
Two steers were removed from the trial on day 56 due to lameness. Cause of removal was not associated with dietary treatment. Hay was approximately 70% neutral detergent fiber (NDF) and 10% crude protein (CP). Total diets were approximately 14% CP during the first half of the trial and 12.5% CP during the second half (Table 2). This difference was not intentional and the cause is speculative. The Control diet had 1.5 to 2 percentage units less protein than the protein supplemented diets. All pens were fed 5 lb/head of their designated supplements from day 1 to 19. Supplement was 38.7% of total DM intake (DMI) during this time (free choice chopped hay was 61.3% of the diet). During the trial, hay intake gradually increased. In order to keep supplement intake at about 35% of the ration, from day 20 to 70, all pens were fed 6 lb of supplement per head. Actual supplement percentage of the total ration averaged 34.7 during days 20 to 70.
Performance data are presented in Tables 3 and 4. All treatment means are presented in Table 3. In general, gains were excellent; well over 2 lb/day. This was likely due in large part to feeding hay in a chopped form. There were no significant interactions for measures of performance. Cattle supplemented with soybean meal (SBM) had the best gains and feed conversion (P < 0 .04) whether they were fed corn or the midds/soyhull diet; those fed the Control diet (without supplemental protein) had the poorest performance and those supplemented with urea were intermediate. In Table 4, the main effects of energy and protein source are presented. Source of energy did not affect rate of gain (P > 0.79) or feed/gain (P > 0.26). In these diets, the effective energy value of the midds/soyhull supplement was equal to corn grain. This effect may have been due to positive associative effects of the midds/soyhull on hay digestibility or negative effects of corn supplementation on hay digestibility or most likely, a combination of both. Total intake was similar for cattle fed both energy sources. If the midds/soyhull supplement resulted in a positive associative effect on digestibility, it did not result in an increase in feed intake. Cattle fed diets supplemented with SBM gain 6.6% faster than those supplemented with urea (P < 0.01). Feed intake was not affected (P > 0.18) by source of protein; therefore, feed conversion was improved (P < 0.02) for SBM supplemented cattle. In summary, cattle fed chopped hay diets supplemented at 35% with a combination of wheat midds and soyhulls benefit from protein supplementation. Cattle fed supplements containing soybean meal grew 6.6% faster and were more efficient than those fed supplements containing urea. Supplements based on corn grain and the midds/soyhull combination resulted in similar daily gains suggesting they have equal "effective" energy value when fed with a forage-based diet.