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Corn often constitutes the main portion of high-concentrate diets fed to feedlot lambs. However, soybean hulls (SH) may be used to replace corn, and may reduce feed costs and the risk of acidosis. The objective of this experiment was to determine the effect of SH inclusion rate in high-concentrate diets on DMI, apparent digestibility of nutrients, N balance, and some rumen constituents. Sixteen ruminally fistulated Santa Inês ram lambs (44.3 ± 5 kg of BW and 6 mo old) were housed in suspended metabolism crates. A randomized complete block design experiment with 4 diets and 4 blocks was used. Blocks were defined by BW, and diets were allotted randomly within block. The control diet contained 70% corn and 0% SH. In the remaining diets, SH replaced corn at the rate of 15, 30, or 45% of the original corn concentration, which resulted in 0, 10.5, 21.0, and 31.4% of SH in the dietary DM. The DMI (kg/d) increased linearly (P < 0.01) with increasing dietary SH inclusion. A trend was observed for linear decreases (P = 0.10) in apparent DM, OM, and nonfiber carbohydrate digestibility, and a trend was observed for an increase (P = 0.08) in NDF digestibility with increasing dietary SH addition. Apparent digestibilities of CP and ether extract and ADF digestibility were not affected by SH inclusion rate. Total ruminal concentration of short-chain fatty acids was affected quadratically (P = 0.03) by diet; acetate concentration increased linearly (P < 0.01), whereas quadratic effects were observed on propionate concentration (P = 0.03) and acetate-to-propionate ratio (P < 0.01) with increasing dietary SH. Ruminal pH increased linearly (P < 0.01) as corn was replaced by SH. Nitrogen retention was not affected by the addition of SH, in spite of a linear increase in urinary N (P < 0.01). The replacement of corn grain with up to 45% SH (31.4% of SH in the dietary DM) resulted in a trend to decrease apparent digestibility of DM and to increase NDF digestibility, presenting a fermentation pattern that would reduce the risk of acidosis. [ABSTRACT FROM AUTHOR]

The objectives of this experiment were to determine the effects of replacing ground corn with soybean hulls (SH) in high-concentrate diets on the growth (56-d period), carcass characteristics, and eating behavior of feedlot lambs. Sixty-four Santa Inês ram lambs (18.3 ± 2.8 kg of BW and 69 ± 5 d of age) were assigned to a randomized complete block design experiment with 8 blocks and 4 diets. The control diet contained 10% coastcross (Cynodon sp.) hay, 70% corn, and no SH (SH0) in the dietary DM. In the remaining diets, SH replaced corn at the rate of 15 (SH15), 30 (SH30), or 45% (SH45) of the original corn concentration, resulting in 0, 10.5, 21.0, or 31.4% SH in the dietary DM. Dry matter intake increased linearly (P < 0.01) when SH replaced ground corn (1.0, 1.0, 1.1, and 1.1 kg/d for SH0, SH15, SH30, and SH45, respectively). There was no effect on ADG of lambs, with values of 276, 278, 282, and 287 g for SH0, SH15, SH30, and SH45, respectively. Feed efficiency decreased linearly (P < 0.01) with SH inclusion. Carcass measures were not affected by SH as a replacement for ground corn. Eating time, expressed as minutes per day and minutes per gram of NDF, showed a quadratic effect (P < 0.05), whereas no effect was observed when expressed as minutes per gram of DM. Rumination, in minutes per day, was not influenced by dietary SH inclusion, but a linear decrease (P < 0.01) was observed when this variable was expressed as minutes per gram of NDF. Soybean hulls can replace up to 45% of the ground corn (31.4% of SH in the dietary DM) in high-concentrate diets fed to feedlot lambs without negative effects on ADG and carcass measures. The linear decrease in feed efficiency (11.6% reduction from SH0 to SH45) suggests that optimal dietary SH inclusion rates should be dictated by the relative costs of SH and corn. [ABSTRACT FROM AUTHOR]