Effects of Distillers Dried Grains with Solubles Sources and Soybean Meal Level on Growth Performance of Late Nursery Pigs

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Summary
Two experiments were conducted to determine the effects of distillers dried grains with solubles (DDGS) source and soybean meal (SBM) level on growth performance of late nursery pigs. A total of 1,064 and 1,011 pigs (PIC 280 × 1050), initially 23.1 and 24.1 lb body weight (BW), were used in Exp. 1 and 2, respectively, with 21 to 27 pigs per pen. For approximately 21 days after weaning, pigs were fed common phase 1 and 2 diets. Then, pens were assigned to treatments in a randomized complete block design. There were 6 treatments in each experiment with 7 pens per treatment. Treatments 1 to 5 were replicated in Exp. 1 and 2, whereas treatment 6 was fed only in Exp. 1 and treatment 7 was fed only in Exp. 2. Treatments 1 to 3 consisted of diets with 23% conventional DDGS (Valero, Aurora, SD) and 21, 27, or 35% SBM. Treatments 4 and 5 were corn-SBM-based diets with 27 or 35% SBM. Treatment 6 consisted of a corn-SBM-based diet with 20% high protein DDGS (HP DDGS; Purestream 40, Lincolnway Energy, LLC, Nevada, IA) replacing the 23% conventional DDGS with the same amount of SBM (21%) as treatment 1 and same neutral detergent fiber (NDF) as treatment 2. Finally, treatment 7 consisted of a diet similar to treatment 2 but with 23% Lincolnway DDGS (Lincolnway Energy, LLC, Nevada, IA) replacing the 23% conventional DDGS. Data were analyzed with the GLIMMIX procedure of SAS. There was no evidence for treatment × experiment interactions, thus data from treatments 1 to 5 were combined. In Exp. 1, pigs fed diets containing HP DDGS had decreased (P < 0.01) average daily gain (ADG) and poorer (P < 0.01) feed-to-gain ratio (F/G) compared to pigs fed diets with conventional DDGS at the same NDF level, conventional DDGS at the same SBM level, or corn-SBM diet. In Exp. 2, there was no evidence for differences (P > 0.10) in performance of pigs fed diets with Lincolnway DDGS or conventional DDGS. Feeding diets with 23% conventional DDGS decreased (P = 0.033) average daily feed intake (ADFI) and improved (P = 0.033) F/G compared to corn-SBM-based diets. Finally, ADG increased (linear, P = 0.001) and F/G Soybean meal (SBM) is a major component of swine diets. It is the most used plantprotein source in swine diets, mainly due to its high digestibility and amino acid profile that complements corn, and consistent processing that removes anti-nutritional factors. 6,7 However, in recent years, U.S. swine diets are formulated with increasing crystalline amino acid amounts and alternative ingredients, such as DDGS or HP DDGS. This is done at the expense of SBM in order to reduce diet cost while still meeting the animals' nutrient requirements. However, recent research suggests that there may be some benefits of feeding high levels of SBM, especially for health-challenged pigs. 8,9 Therefore, we hypothesized that pigs fed diets with high DDGS or HP DDGS inclusions or high crystalline amino acid amounts may have reduced growth performance due to the reduction in dietary SBM. The objective of this study was to evaluate two DDGS sources, a HP DDGS source, and SBM level on growth performance of late nursery pigs.

Procedures
The Kansas State University Institutional Animal Care and Use Committee approved the protocols used in these experiments. Two experiments were conducted at a commercial nursery research facility in southwest Minnesota. The barns were mechanically ventilated and had completely slatted flooring. Each pen (12.1 × 7.5 ft) was Swine Day 2018 equipped with a 6-hole, stainless steel, dry self-feeder and a pan waterer. Experimental diets were manufactured at New Horizon Farms feed mill in Pipestone, MN. Feed additions were delivered and recorded by a robotic feeding system (FeedPro; Feedlogic Corp., Wilmar, MN). Representative diet samples were obtained from each treatment. Samples were analyzed for dry matter (DM), crude protein (CP), Ca, P, Na, and Cl (Ward Laboratories, Inc., Kearney, NE).
In Exp. 1, 1,064 pigs (PIC 280 × 1050; initial average BW of 23.1 lb) were used in a 27-d growth trial with 22 to 27 pigs per pen and 7 replicates per treatment. In Exp. 2, 1,011 pigs (PIC 280 × 1050; initial average BW of 24.1 lb) were used in a 27-d growth trial with 21 to 27 pigs per pen and 7 replicates per treatment. Pigs were sourced from two sow farms and weaned at approximately 19 and 20 d of age in Exp. 1 and 2, respectively. In both experiments, the barn was filled in two days. Pigs were fed common phase 1 and 2 diets for approximately 21 d after placement and before the start of the experiments. Then, pens of pigs were allotted to treatments in a randomized complete block design with BW, sow farm, and fill date as the blocking factors.
Each experiment had 6 treatments. Treatments 1 to 5 were replicated in Exp. 1 and 2, whereas treatment 6 was fed only in Exp. 1 and treatment 7 was fed only in Exp. 2. Treatments 1 to 3 consisted of diets with 23% conventional DDGS (Valero, Aurora, SD) with 21, 27, or 35% SBM. Treatments 4 and 5 were corn-SBM-based diets with 27 or 35% SBM. Treatment 6 consisted of a corn-SBM diet with 20% HP DDGS (Purestream 40, Lincolnway Energy, LLC, Nevada, IA) replacing the 23% conventional DDGS with the same SBM level as treatment 1 and same NDF as treatment 2. Finally, treatment 7 was a diet similar to treatment 2 but with 23% Lincolnway DDGS (Lincolnway Energy, LLC, Nevada, IA) replacing the 23% conventional DDGS. Soybean meal levels were obtained by manipulating the inclusion of crystalline amino acids (Table 1) Pens were weighed and feed disappearance was measured on d 0, 7, 14, 21, and 27 in Exp. 1 and 2 to determine ADG, ADFI, and F/G. Data were analyzed as a randomized complete block design with block as a random effect and pen as the experimental unit.

Results and Discussion
The proximate analysis of the DDGS sources and diets were consistent with formulated estimates (Tables 2 and 3).
In Exp. 1, pigs fed diets with HP DDGS had decreased (P < 0.01) ADG and poorer (P < 0.01) F/G compared to pigs fed diets with conventional DDGS at the same NDF level, conventional DDGS at same SBM level, or corn-SBM diet (Table 4 and 5). Results suggest that nutrient loadings for HP DDGS, such as amino acid content or digestibility, may be overestimated.
In Exp. 2, there was no evidence for differences (P > 0.10) in performance of pigs fed diets with Lincolnway DDGS or conventional DDGS (Table 6).
Because there was no evidence for treatment × experiment interaction (P > 0.10), data from treatments 1 to 5 from each experiment were combined (Tables 7 and 8). Feeding diets with 23% conventional DDGS decreased (P = 0.033) ADFI and improved (P = 0.033) F/G compared to corn-SBM diets. This suggests that the net energy of conventional DDGS, calculated as approximately 88% of corn net energy, was underestimated in diet formulation. Based on caloric efficiency, determined as kcal net energy required per pound of gain, the net energy of the conventional DDGS used in this study was approximately 93% of the net energy of corn. Furthermore, the lack of evidence for differences between pigs fed conventional DDGS and Lincolnway DDGS in Exp. 2 indicates that net energy of the latter was also underestimated.
When analyzed as part of the factorial without or with 23% conventional DDGS, pigs fed diets with 35% SBM had marginally greater (P = 0.052) ADG and improved (P = 0.001) F/G compared to pigs fed diets with 27% SBM. When comparing SBM level to diets with 23% conventional DDGS, ADG increased (linear, P = 0.001) and F/G improved (quadratic, P = 0.007) with increasing SBM, and the response was mainly driven by the treatment with 35% SBM. Researchers have suggested pigs under health challenge have better performance when fed high SBM level inclusions. 7,8 Although not fully understood, some of the benefits have been attributed to antiinflammatory and immune system modulation abilities of isoflavones and saponins present in SBM. 12 In conclusion, it seems that nutrient loadings of HP DDGS were overestimated, which resulted in poorer growth performance when replacing SBM or conventional DDGS. Pigs fed diets with conventional DDGS had improved F/G, which indicates that the net energy was underestimated in conventional and Lincolnway DDGS. Finally, feeding increasing SBM levels resulted in improved performance in late nursery pigs. Future research should focus on reevaluating HP DDGS with an updated nutrient profile, and to better understand the potential benefits of high levels of SBM on growth performance of late nursery pigs.      F/G = feed-to-gain ratio.