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Extrusion Processing of Low-Inhibitor Soybeans Improves Growth Performance of Early-Weaned Pigs |
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I. H. Kim, J. D. Hancock, D. B. Jones, P. G. Reddy |
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| Abstract |
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Two experiments were conducted to determine the effects of roasting and extrusion on nutritional value of conventional and low-inhibitor soy beans for nurser-age pigs. In Exp. 1, 100 weaning pigs (7.5 kg average initial BW were used in a 35-d growth assay to determine the effects of processing method (roasting in a Rast-A-TronTM raster vs extrusion in an Insta-ProTM extruder) on the nutritional value of Williams 82 soybeans with (+K) and without (-K) gene expression for the Kunitz trypsin inhibitor. Treatments were 48% soybean meal with added soybean oil, +K roasted, +K extruded, -K roasted and -K extruded. All diets were formulated to contain 3.5 Mcal DE/kg, with 0.92% lysine for d 0 to 14 and 0.76% lysine for d 14 to 35 of the experiment. The lysine concentrations were 80% of NRC (1988) recommendations to accentuate difference in response to protein quality and lysine availability. For d 0 to 14, pigs fed extruded soybeans (+K and -K) had greater ADG (p<0.001), ADFI (p<0.09) and gain/feed (p<0.01) than pigs fed roasted soybeans. For d 14 to 35 and overall, the same effects were noted, I.e., pigs fed extruded soybeans had greater ADG, ADFI and gain/feed than pigs fed roasted soybeans (p<0.03). Also, pigs fed -K soybeans were more efficient (p<0.008) than pigs fed +K soybeans. In Exp. 2, 150 weanling pigs (7.0 kg average initial BW) were used in a 35-d growth assay. All diets were formulated to contain 3.5 Mcal DE/kg, with 1.25% lysine for d 0 to 14 and 1.10% lysine for d 14 to 35 of the experiment. The lysine concentrations were formulated to be in excess of NRC recommendation to determine if differences in nutritional value of the soybean preparations could be detected in protein-adequate diets. For d 0 to 14 (p<0.06), 14 to 35 (p<0.03) and 0 to 35 (p<0.02), pigs fed extruded soybeans had greater ADG and gain/feed than pigs fed roasted soybeans. Apparent digestibilities of DM, N and GE were greater for diets with extruded soybeans than diets with roasted soybeans and diets with soybean meal and soybean oil were intermediate. The response to extrusion processing was greater with -K than +K soybeans, with pigs fed extruded -K soybeans having the greatest growth performance and nutrient digestibilities and lowest skin-fold thickness of any treatment. In conclusion, extrusion yielded a full-fat soy product of greater nutritional value than roasting. Also, selection against genetic expression of the Kunitz trypsin inhibitor improved nutritional value of the resulting soybean preparations. |
| Keywords:
Weanling Pigs; Soybeans; Extrusion; Roasting; Trypsin Inhibitor; Immunology |
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