ACID STEEPING OF CORN AND GRAIN-SORGHUM - EFFECT ON NUTRIENT DIGESTIBILITY IN GROWING PIGS

Two experiments were conducted to determine the effect of acid steeping of whole com and grain sorghum on nutrient digestibility in growing pigs. In the first experiment, com and cream, yellow and bronze sorghum hybrids were steeped in a 0.25% sulfurous acid solution (corn for 48 h at 52-degrees-C and sorghum for 24 h at 48-degrees-C) after which the steeping solution was discarded. Digestibility of diets containing the grains was measured with 48 barrows (27.5+/-2.1 kg). Steeping increased dry matter (DM) and energy digestibility of corn-based diets, but had little effect or a negative effect on the digestibility of sorghum-based diets (grain X steeping interaction, P<0.01). Bronze sorghum had less digestible DM and a lower digestible energy (DE) and metabolizable energy (ME(n)) contents (the latter corrected for nitrogen balance) than yellow and cream sorghum (P<0.07). In the second experiment, com and yellow and bronze sorghum hybrids were steeped in a 0.3% sulfurous acid, 0.1% lactic acid solution for 0, 12, 24 or 48 h. Steeping solution was discarded after steeping. Digestibility was measured with 72 barrows (36.8+/-4.0 kg). In general, steeping for either 12 or 24 h reduced digestibility of corn and grain sorghum. However, 48 h of steeping did not affect digestibility in comparison with non-steeped grains, especially for corn and yellow sorghum (steeping time quadratic, P<0.05). Steeping bronze sorghum for either 12, 24 or 48 h reduced digestibility (grain X steeping time interaction, P<0.06). Nitrogen digestibility was greater for corn diets than for sorghum diets (P<0.001). Diets containing bronze sorghum had more digestible DM and higher DE and ME(n) contents than diets containing yellow sorghum. Steeping corn and grain sorghum without recovery of soluble or suspended substances from the steeping solutions resulted in little improvement in nutrient digestibility.