The effects of soybean hulls on nursery pig growth performance The effects of soybean hulls on nursery pig growth performance

Two experiments were conducted to evaluate the effects of soybean hulls on growth performance of nursery pigs. In both experiments, pens of pigs were balanced by initial BW and randomly allotted to 1 of 5 dietary treatments with 6 replications per treat-ment. In Exp. 1, a total of 210 nursery pigs (PIC, 337 × 1050, initially 14.7 lb and 28 d of age) were used in a 34-d experiment. Diets contained increasing amounts of soybean hulls (0, 5, 10, 15, and 20%) and were not balanced for energy. Overall (d 0 to 34), pigs fed increasing soybean hulls had decreased ADG (linear, P < 0.01) and poorer F/G (linear, P < 0.001), with no change in ADFI ( P > 0.23). Despite the linear response, the greatest decreases in pig performance were observed as soybean hulls were added at 10% or greater of the diet; those fed only 5% of the diet were similar to control pigs. In Exp. 2, 210 nursery pigs (PIC, 337 × 1050, initially 29.9 lb) were used in a 20-d study. Pigs were fed a common diet for 14 d after weaning. The 5 corn-soybean meal– based diets were arranged in a 2 × 2 + 1 factorial, including a corn-soybean meal control diet without soybean hulls and diets containing 10 or 20% soybean hulls either balanced on an NE basis or not. The diets balanced for NE contained 3.6 and 7.15% added fat (soybean oil) in the 10 and 20% soybean hull diets to achieve the same NE value as the control diet. Overall


Summary
Two experiments were conducted to evaluate the effects of soybean hulls on growth performance of nursery pigs.In both experiments, pens of pigs were balanced by initial BW and randomly allotted to 1 of 5 dietary treatments with 6 replications per treatment.In Exp. 1, a total of 210 nursery pigs (PIC, 337 × 1050, initially 14.7 lb and 28 d of age) were used in a 34-d experiment.Diets contained increasing amounts of soybean hulls (0, 5, 10, 15, and 20%) and were not balanced for energy.Overall (d 0 to 34), pigs fed increasing soybean hulls had decreased ADG (linear, P < 0.01) and poorer F/G (linear, P < 0.001), with no change in ADFI (P > 0.23).Despite the linear response, the greatest decreases in pig performance were observed as soybean hulls were added at 10% or greater of the diet; those fed only 5% of the diet were similar to control pigs.
In Exp. 2, 210 nursery pigs (PIC, 337 × 1050, initially 29.9 lb) were used in a 20-d study.Pigs were fed a common diet for 14 d after weaning.The 5 corn-soybean mealbased diets were arranged in a 2 × 2 + 1 factorial, including a corn-soybean meal control diet without soybean hulls and diets containing 10 or 20% soybean hulls either balanced on an NE basis or not.The diets balanced for NE contained 3.6 and 7.15% added fat (soybean oil) in the 10 and 20% soybean hull diets to achieve the same NE value as the control diet.
Overall (d 0 to 20), pigs fed increasing soybean hulls had decreased ADG (linear, P < 0.01) regardless of formulation method; however, pigs fed increasing amounts of soybean hulls without added fat were similar in ADFI but had poorer F/G (linear, P < 0.001).Pigs fed diets containing soybean hulls balanced for NE had decreased ADFI (P < 0.001) but improved F/G (P < 0.001) compared with pigs fed soybean hulls with no added fat, resulting in F/G similar to the control-fed pigs.

Introduction
Soybean hulls are a readily available co-product of the solvent extraction of whole soybeans that could be used in swine diets across the Midwest, but because of soybean hulls' low energy value (corn NE = 1,202 kcal/lb; soybean hulls NE = 455 kcal/lb;

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INRA 2004 1 ) and a lack of research, few swine producers use soybean hulls in nursery pig diets.When including soybean hulls in corn-soybean meal-based diets, the energy content will decrease unless diets are balanced for energy by including added fat.
Due to limited research on added soybean hulls in nursery diets, the first objective of these two studies was to evaluate the effects of increasing soybean hulls (0 to 20%) on nursery pig performance.Our second objective was to determine whether balancing diets on an NE basis by adding dietary fat influenced the pigs' response to soybean hulls.

Procedures
The Kansas State University Institutional Animal Care and Use Committee approved the protocol used in this experiment.Both studies were conducted at the K-State Swine Teaching and Research Center in Manhattan, KS.
Soybean hull samples were collected and submitted to Ward Laboratories, Inc. (Kearney, NE) for analysis of DM, CP, ADF, NDF, crude fiber, Ca, and P (Table 1).Bulk density of the soybean hulls (Table 1) and complete diets were also determined (Tables 2 and 3).
In Exp. 1, a total of 210 pigs (PIC 327 × 1050, initially 14.7 lb and 28 d of age) were used.Pigs were allotted to pens by initial BW, and pens were assigned to 1 of 5 treatments in a completely randomized design with 7 pigs per pen and 6 replications per treatment.Experimental diets contained increasing amounts of soybean hulls: 0, 5, 10, 15, or 20% and were not balanced to a constant NE (Table 2).Pig weight and feed disappearance were measured on d 0, 7, 13, 20, 27, and 34 of the trial to determine ADG, ADFI, and F/G.All diets were fed in meal form and were prepared at the K-State Animal Science Feed Mill in Manhattan, KS.
In Exp. 2, a total of 210 pigs (PIC 327 × 1050, initially 29.9 lb) were used in a 20-d growth trial to determine the effects of increasing dietary soybean hulls with or without a constant NE level on nursery pig performance.All pigs were initially fed a starter diet followed by a Phase 2 diet for 14 d after weaning.Pigs were allotted to pens by initial BW, and pens were assigned to 1 of 5 treatments in a completely randomized design with 7 pigs per pen and 6 replications per treatment.The 5 treatment diets included a control diet without soybean hulls and diets containing 10% or 20% soybean hulls either balanced on an NE-basis or not.The diets balanced for NE contained 3.6 and 7.15% added soybean oil in the 10 and 20% soybean hull diets to achieve the same NE as the control diet (Table 3).Pig weight and feed disappearance were measured on d 0, 6, 13, and 20 of the trial to determine ADG, ADFI, and F/G.All diets were fed in meal form and were prepared at the K-State Animal Science Feed Mill.
In both studies, each pen contained a 4-hole, dry self-feeder and a nipple waterer to provide ad libitum access to feed and water.Pens had wire-mesh floors and allowed approximately 3 ft 2 /pig.

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Data were analyzed as a completely randomized design using the PROC MIXED procedure of SAS (SAS Institute, Inc., Cary, NC) with pen as the experimental unit.In Exp. 1, contrasts were used to compare linear and quadratic effects of increasing soybean hulls.Contrasts in Exp. 2 were used to compare linear and quadratic effects of increasing soybean hulls with and without balancing for NE.In addition, diet formulation method and soybean hull level effects were also tested, along with interactions between soybean hulls and diet formulation method.Results were considered significant at P ≤ 0.05 and a trend at P ≤ 0.10.

Results and Discussion
In Exp. 1, increasing soybean hulls resulted in higher fiber and NDF and lower energy and decreased bulk densities compared with the corn-soybean meal control diet (Table 2).For every dietary period, pigs fed increasing soybean hulls had decreased (linear, P < 0.01) ADG and poorer (linear, P < 0.001) F/G, with no change (P > 0.21) in ADFI.Despite the linear response for ADG and F/G, much of this effect was observed in pigs fed 10% soybean hulls or greater (Table 4).Although F/G became worse, increasing soybean hulls in the diet improved (linear, P < 0.02) caloric efficiency on an NE basis.Nursery pigs will attempt to consume feed to meet an energy requirement.Because of the low bulk density and potential for increased gut fill caused by high amounts of soybean hulls, pigs in this experiment were unable to maintain energy intake on lower-energy diets containing more than 5% soybean hulls.
Based on the results in Exp. 1, 5% soybean hulls could be used with no negative effects on growth performance, but using more than 5% resulted in poorer F/G and ADG.Therefore, the objective of Exp. 2 was to determine if balancing diets containing soybean hulls on an NE basis with added fat could restore performance similar to cornsoybean diets.
Overall (d 0 to 20), pigs fed increasing soybean hulls had decreased ADG (linear, P < 0.003), whether or not diets were formulated to a constant NE.When diets were not balanced for NE (no added fat), ADFI did not change, but poorer (linear, P < 0.0001) F/G and caloric efficiency on an NE basis (P < 0.05) were observed.When adding fat to diets containing soybean hulls to increase NE, F/G was similar to pigs fed the control diet and improved F/G (P < 0.0001) compared with pigs fed diets not balanced for NE.Overall, increasing soybean hulls decreased (linearly, P < 0.0002) ADFI.The fact that pigs fed diets balanced on a NE basis were identical to the controlfed pigs in F/G suggests that the NE value used for the soybean hulls in this study was appropriate.
In conclusion, soybean hulls are a low-energy, low bulk density ingredient that can be used in nursery pig diets at 5% with no negative effects on growth performance.Conversely, high amounts (greater than 5%) of soybean hulls can restrict performance, probably because of increased fiber and low diet bulk density.Formulating diets on an NE basis by adding fat can result in similar F/G but still fail to maintain ADG and ADFI.These studies suggest that more research is needed to understand how lowenergy ingredients such as soybean hulls can potentially affect gut fill, feed intake, and growth. 1 Phase 1 diets were fed from d 0 to 13. 2 Phase 2 diets were fed from d 13 to 34. 3 Phyzyme 600 (Danisco, Animal Nutrition, St. Louis, MO) provided 231 phytase units (FTU)/lb, with a release of 0.10% available P. 4 Soybean hulls ADF and NDF values are from INRA (Institut National de la Recherche Agronomique), 2004.All other values taken from NRC, 1998. 5Diet samples collected from the top of each feeder during each phase.

Table 3 .
Diet composition (Exp.2, as-fed basis) 3Soybean hulls ADF and NDF values are from INRA (Institut National de la Recherche Agronomique), 2004.All other values taken from NRC, 1998.3Dietsamples collected from the top of each feeder during each phase.

Table 4 .
1he effects of soybean hulls in nursery diets on nursery pig performance (Exp.1)1

Table 5 .
1he effects of soybean hulls and diet NE on nursery pig performance1