Two experiments were conducted to determine the relationship between corn particle size and soybean meal treatment on growth, diet digestibility, and nitrogen balance of growing steers. In the first experiment, 40 medium-frame beef steers (250 ± 11 kg) were fed individually for 140 d a diet based on grass silage offered for ad libitum consumption and supplemented with either 3.5 kg of DM d-1 of cracked corn (CC) or ground corn (GC) and with 450 g of DM d-1 of solvent extracted (SS) or lignosulfonate-treated soybean meal (Soypass™ SP). Dry matter intake was not affected by treatments and averaged 8.6 ± 0.3 kg d-1 (P > 0.10). Average daily gain was higher for animals receiving the ground corn than those fed cracked corn. Feed to gain ratio was not affected by treatments. There was an interaction between treatments for plasma urea-N concentration, with source of soybean meal having no effect with CC. When compared with SS, SP supplement reduced plasma urea-N when fed with GC. No effect of soybean meal and its interaction with corn processing was observed on growth performance. In the second experiment four additional steers were used in a 4 × 4 Latin square design to evaluate diet digestibility and nitrogen balance. There was an interaction between treatments for starch apparent digestibility and N retained, the values being respectively, 90, 86, 93, and 92% (SEM = 1.2; P < 0.01) and 36, 42, 44 and 41 g d-1 (SEM = 2.8; P < 0.03) for CCSS, CCSP, GCSS and GCSP, respectively. Altogether, the results indicate a slight advantage to reduce particle size of corn in growing steers fed grass silage. However, soybean meal treatment resulted in limited effects on growth and digestion. Key words: Rumen carbohydrate, undegradable protein, performance, steers
Feeding strategies for improving productivity of growing steers fed grass silage
