Evaluation of High-Protein Distillers Dried Grains on Growth Performance and Carcass Characteristics of Growing-Finishing Pigs

A total of 1,890 growing-finishing pigs (PIC; 359 × 1050; initially 59.8 ± 1.3 lb) were used in a 124-d growth trial to compare the effects of high-protein distillers dried grains (HPDDG) or conventional distillers dried grains with solubles (DDGS) on growth performance and carcass characteristics. Conventional DDGS contained 29.0% CP, 0.48% standardized ileal digestible (SID) Lys, and 9.2% oil, whereas HPDDG contained 39.3% CP, 0.68% SID Lys, and 11.1% oil. All diets were formulated on an equal SID Lys-basis with diets containing HPDDG having less soybean meal than diets with conventional DDGS. There were 27 pigs per pen and 14 pens per treatment. Treatment diets were corn-soybean meal-based and arranged in a 2 × 2 + 1 factorial with main effects of DDG source (conventional DDGS or HPDDG) and level (15 or 30%). A corn-soybean meal-based diet served as the control and allowed linear and quadratic level effects to be determined within each DDG source. Pens of pigs were assigned to 1 of the 5 treatments in a randomized complete block design with initial weight as a blocking factor. Data were analyzed using the lme4 package in R (version 3.5.2) with pen as experimental unit. Overall, there were no differences observed in ADG between pigs fed either DDG source or level. Pigs fed HPDDG had decreased (linear, P < 0.001) ADFI and improved F/G compared with those fed conventional DDGS. Increasing either conventional DDGS or HPDDG decreased carcass yield and HCW (linear, P < 0.02); however, there were no differences between pigs fed HPDDG or conventional DDGS. Iodine value (IV) was greater (P < 0.001) in pigs fed HPDDG than conventional DDGS, and IV increased (linear, P < 0.02) with increasing DDG source. In summary, these data suggest that pigs fed HPDDG had better F/G, but greater IV compared with pigs fed conventional DDGS, probably due to the difference in oil content.

Summary A total of 1,890 growing-finishing pigs (PIC; 359 × 1050; initially 59.8 ± 1.3 lb) were used in a 124-d growth trial to compare the effects of high-protein distillers dried grains (HPDDG) or conventional distillers dried grains with solubles (DDGS) on growth performance and carcass characteristics. Conventional DDGS contained 29.0% CP, 0.48% standardized ileal digestible (SID) Lys, and 9.2% oil, whereas HPDDG contained 39.3% CP, 0.68% SID Lys, and 11.1% oil. All diets were formulated on an equal SID Lys-basis with diets containing HPDDG having less soybean meal than diets with conventional DDGS. There were 27 pigs per pen and 14 pens per treatment. Treatment diets were corn-soybean meal-based and arranged in a 2 × 2 + 1 factorial with main effects of DDG source (conventional DDGS or HPDDG) and level (15 or 30%). A corn-soybean meal-based diet served as the control and allowed linear and quadratic level effects to be determined within each DDG source. Pens of pigs were assigned to 1 of the 5 treatments in a randomized complete block design with initial weight as a blocking factor. Data were analyzed using the lme4 package in R (version 3.5.2) with pen as experimental unit. Overall, there were no differences observed in ADG between pigs fed either DDG source or level. Pigs fed HPDDG had decreased (linear, P < 0.001) ADFI and improved F/G compared with those fed conventional DDGS. Increasing either conventional DDGS or HPDDG decreased carcass yield and HCW (linear, P < 0.02); however, there were no differences between pigs fed HPDDG or conventional DDGS. Iodine value (IV) was greater (P < 0.001) in pigs fed HPDDG than conventional DDGS, and IV increased (linear, P < 0.02) with increasing DDG source. In summary, these data suggest that pigs fed HPDDG had better F/G, but greater IV compared with pigs fed conventional DDGS, probably due to the difference in oil content.

Introduction
Distillers dried grains with solubles is a co-product of the ethanol industry that is widely used in growing-finishing swine diets. Recently, new processing techniques are available to remove fibrous components before fermentation that produce a high-protein distillers dried grains (HPDDG) with approximately 40% crude protein. The new product generated has a different chemical composition and nutritive value for swine diets than conventional DDGS. Therefore, it is critical to characterize the effects of HPDDG on growth performance and carcass characteristics of growing-finishing pigs.

Procedures
The Kansas State University Institutional Animal Care and Use Committee approved the protocol used in this experiment. The study was conducted at a commercial research-finishing site in southwest Minnesota. The barn was naturally ventilated and double-curtain-sided. Each pen was equipped with a 5-hole stainless steel dry self-feeder and a bowl waterer for ad libitum access to feed and water.
Two groups of approximately 945 pigs (1,890 total pigs; PIC 359 × 1050; initially 59.8 ± 1.3 lb) were used in a 124-d growth trial. Pigs were housed in mixed gender pens with 27 pigs per pen and 14 pens per treatment (7 replications per barn). Daily feed additions to each pen were accomplished using a robotic feeding system (FeedPro, Feedlogic Corp., Wilmar, MN) able to record feed amounts for individual pens. The treatments were structured as a randomized complete block design and arranged in a 2 × 2 +1 factorial with main effects of DDG source (conventional DDGS and HPDDG) and level (15 or 30%). A corn-soybean meal-based diet served as the control and allowed linear and quadratic level effects to be determined within each DDG source. Nutrient and SID amino acid values for DDGS were derived from NRC 5 and nutrient and SID amino acid values for HPDDG were derived from Rho. 6 Conventional DDGS contained 29.0% CP, 0.48% standardized ileal digestible (SID) Lys, and 9.2% oil, whereas HPDDG contained 39.3% CP, 0.68% SID Lys, and 11.1% oil. All diets were formulated on an equal SID Lys-basis with diets containing HPDDG having less soybean meal than diets with conventional DDGS. Corn, conventional DDGS, and HPDDG used in this trial were analyzed for proximate analysis, amino acid profile (Table 1), and mycotoxins ( Pigs were weighed approximately every 14 days from d 0 to 124 of the trial to determine ADG, ADFI, and F/G. On d 103, the 3 heaviest pigs in each pen were selected and marketed. These pigs were included in the growth performance data but not in carcass data. On the last day of the trial, final pen weights were taken, and the remaining pigs were tattooed with a pen identification number and transported to a USDA-inspected packing plant (JBS Swift, Worthington, MN) for carcass data collection. Carcass measurements included HCW, loin depth, backfat, percentage lean, and fat iodine value (IV). Fat samples for IV were collected from the shoulders of carcasses of 14 pigs per treatment. Percentage lean was calculated from a plant proprietary equation. Carcass yield was calculated by taking the pen average HCW divided by the pen average final live weight obtained at the farm.
Data were analyzed as a randomized complete block design for two-way ANOVA using the lmer function from the lme4 package in R program (R Core Team, 2019) with pen considered the experimental unit, initial BW as blocking factor, and treatment as fixed effect. Phases 1 and 2 were combined to represent the grower phase, while phases 3 and 4 were combined and referred to as the finisher phase for growth performance analysis. Predetermined contrasts were used to evaluate the main effects and interactive effects of DDG source × level among treatments. These contrasts were also used to examine the linear and quadratic responses due to increasing DDG inclusion level within DDG source using the control diet (as 0% inclusion level) and the 15% and 30% diets. All results were considered significant at P ≤ 0.05 and marginally significant at 0.05 < P ≤ 0.10.

Results and Discussion
High-protein distillers dried grains had a greater crude protein and fat content than conventional DDGS (Table 1). The fumonisin concentration measurements were higher in HPDDG than conventional DDGS and ranged from approximately 8 to 15 ppm vs. only 200 to 300 ppb in conventional DDGS. Zearalenone concentrations were also higher in HPDDG than conventional DDGS and ranged from 250 to 350 ppb in HPDDG to 100 to 145 ppb in conventional DDGS. Vomitoxin concentrations were generally similar among DDG sources and ranged from approximately 0.8 to 1.0 ppm (Table 2). Chemical analysis (Tables 3 and 4) of treatment diets for dry matter, crude protein, calcium, phosphorus, neutral detergent fiber, and ether extract were within formulated ranges.
In the grower phase (day 0 to 55), increasing either DDG source decreased (linear, P < 0.001) ADG (Table 5). In the finishing phase (day 55 to 124), increasing conventional DDGS tended to decrease (quadratic, P < 0.065) ADG. However, there were no differences observed in overall ADG. Despite no overall changes in ADG among treatments, increasing conventional DDGS or HPDDG decreased (linear, P < 0.04 and P < 0.065, respectively) final body weight (BW). Increasing HPDDG decreased (linear, P ≤ 0.002) ADFI and improved F/G in both phases and the overall period,

Swine Day 2020
whereas there was no change in ADFI or F/G among pigs fed conventional DDGS. The improvement in F/G of pigs fed increasing HPDDG compared to conventional DDGS may be due to the higher oil content of HPDDG.
Based on the improved F/G and decreased ADFI in pigs fed HPDDG, its energy content appears to be greater than the conventional DDGS used in this study. The improvement in F/G of pigs fed increasing HPDDG compared to conventional DDGS may be due to the higher oil content or improved nutrient digestibility in HPDDG. By calculating the caloric efficiency (CE) of diets using procedures of Cemin et al., 8 CE was linearly improved (P = 0.033) as the inclusion level of HPDDG increased. Therefore, we suspected that the net energy (NE) of HPDDG was underestimated. For CE of HPDDG diets to be identical to the control diet, the NE of HPDDG would have to be 103.4% of the energy of corn, which was greater than the value (97.3%) 8 used for diet formulation.
For carcass characteristics, increasing either conventional DDGS or HPDDG decreased carcass yield and HCW (linear, P < 0.02). There were no differences among dietary treatments in back fat, loin depth, or percentage lean. Carcass fat iodine value (IV) was greater (P < 0.001) in pigs fed HPDDG than conventional DDGS, and IV increased (linear, P < 0.02) with increasing either DDG source. Like the improvements in F/G, the change in IV between pigs fed HPDDG and conventional DDGS may be due to the differences in oil content.
In summary, these data suggest that feeding pigs up to 30% HPDDG may have economic advantages because of its amino acid profile and improved F/G compared with feeding pigs conventional DDGS. However, caution must be used with the type of HPDDG used because of the different nutrient profiles, especially AA profile, oil, and energy content. An accurate AA profile allows adjustment of SID Ile:Lys, Leu:Lys, Trp:Lys, and Val:Lys to avoid BCAA imbalance that may cause reduced growth performance. A potential concern with the HPDDG used in this study is the high oil content, which leads to increased carcass fat IV, resulting in higher unsaturated fat in the carcass. In addition, the dietary branched-chain amino acid ratio should be considered to maintain growth performance.    Phases 3 and 4 were fed from 60 to 110 and 110 to 160 lb, respectively. At least 6 representative samples of each diet were collected for each treatment, homogenized, and submitted for proximate analysis (Ward Laboratories, Inc., Kearney, NE). Phases 3 and 4 were fed from 160 to 220 and 220 lb to marketing, respectively.  Adjusted using HCW as covariate.