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Evaluation of increasing digestible threonine to lysine ratio in corn–soybean meal diets without and with distillers dried grains with solubles on growth performance of growing-finishing pigs

Evaluation of increasing digestible threonine to lysine ratio in corn–soybean meal diets without... Translational Animal Science, 2022, 6, 1–6 https://doi.org/10.1093/tas/txac058 Advance access publication 6 May 2022 Non Ruminant Nutrition Evaluation of increasing digestible threonine to lysine ratio in corn–soybean meal diets without and with distillers dried grains with solubles on growth performance of growing-finishing pigs † † †,1 †, Andres F. Tolosa, Mike D. Tokach, Robert D. Goodband, Jason C. Woodworth, † ‡, Joel M. DeRouchey, and Jordan T. Gebhardt Department of Animal Sciences and Industry, College of Agriculture, Kansas State University, Manhattan, KS 66506-0201, USA Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506-0201, USA Corresponding author: Goodband@ksu.edu ABSTRACT Corn distillers dried grains with solubles (DDGS) is commonly available and often can lower diet cost for swine diets. This corn co-product is recognized to be a source of dietary insoluble fiber, which can not only increase the villous length of the gut mucosa but also increase intestinal production of mucin. Mucin structure, functions, and synthesis are correlated to Thr intake; consequently, the dietary Thr level may need to be increased when feeding an insoluble fiber source such as corn–DDGS. Thus, the objective of this study was to evaluate if feeding standardized ileal digestible (SID) Thr:Lys ratio at or above the estimated requirement in diets without and with DDGS would influence growth performance in finishing pigs. A total of 2,160 pigs (PIC 337 × 1,050; initially 35.1 ± 0.5 kg) were used in a 112-d growth trial. Pigs were randomly assigned to pens (27 pigs per pen) in a randomized complete block design by body weight (BW) with 20 replications per treatment. Pens of pigs were allotted to one of four dietary treatments that were arranged in a 2 × 2 factorial with main effects of dietary Thr level (normal vs. high) and DDGS (without or with). Treatment diets were formulated in four phases from 34 to 57, 57 to 79, 79 to 104, and 104 to 130 kg BW. Diets with high DDGS were formulated to include 40% DDGS in phases 1 and 2, 30% in phase 3, and 15% in phase 4. The normal Thr diets were formulated to contain 61%, 62%, 63%, and 65% SID Thr:Lys ratios for the four dietary phases, respectively. High Thr diets had SID Thr:Lys ratios of 67%, 68%, 69%, and 72%, respectively. There were no interactions (P > 0.10) observed in any phase or overall between Thr level and added DDGS. For the overall period (day 0 to 112), pigs fed diets without DDGS had increased (P < 0.001) average daily gain (ADG) but reduced (P < 0.001) average daily feed intake (ADFI), leading to increased (P < 0.001) feed efficiency (gain-to-feed ratio [G:F]). There was no evidence for difference ( P > 0.10) between pigs fed diets formulated at normal or high SID Thr:Lys ratio. In summary, feeding high levels of DDGS decreased ADG and increased ADFI, which resulted in decreased G:F and lower final BW, regardless of the dietary SID Thr:Lys ratio level. In the current study, increasing the level of digestible Thr in a diet that contained a highly insoluble fiber source did not increase the growth performance of grow-finish pigs. Key words: DDGS, grow-finish pigs, growth, insoluble fiber, threonine INTRODUCTION pig. The NRC (2012) suggests that the dietary requirement for standardized ileal digestible (SID) Thr is 60% to 65% Early research by Wang and Fuller (1989) categorized Thr as of that of SID Lys for pigs from 25 to 135  kg body weight the first limiting amino acid for maintenance, which suggests (BW). However, these minimum requirements may change that the utilization of Thr for protein deposition is less than depending on diet formulation and fiber type of the diet (Zhu that for other body needs. The primary reason for this may et al., 2005). be the extensive use of Thr by splanchnic tissues, resulting Furthermore, the abundant availability and lower cost of in some inefficiency of Thr conversion to body protein and corn distillers dried grains with solubles (DDGS) have allowed greater utilization of Thr by intestinal tissue ( Le Flocʹh and nutritionists to partially replace corn, soybean meal, and sup - Seve, 2005). These authors noted that labeled enrichments plemental phosphorus, reducing diet cost for grow-finish pigs. of Thr-bound protein were quite high in the pancreas and However, high concentrations of insoluble fiber in DDGS re - the mucosa compared with that of the liver, which led to the sult in an increased passage rate of chyme and increased en - conclusion that Thr incorporation in mucosa protein and the dogenous losses of digestive enzymes, enterocytes, and mucin pancreas would be very important ( Le Flocʹh and Seve, 2005 ). (Dilger et al., 2004). Therefore, greater inclusion of DDGS in Similarly,Myrie et al. (2003) suggested that an increase in diets may potentially influence mucin secretion and secretion, mucin production reduced body Thr retention. As intestinal which, in part, may impact gastrointestinal epithelial cells,- di tissue increases in size as the pig grows, mucin production gestive enzymes, and mucosal secretions of which Thr is a could increase, and thus, the requirement for Thr would also major component (Montagne et al., 2003). increase to support the intestinal tract and growth of the Received March 2, 2022 Accepted May 3, 2022. Published by Oxford University Press on behalf of the American Society of Animal Science 2022. This work is written by (a) US Government employee(s) and is in the public domain in the US. 2 Tolosa et al. In a recent study, Mathai et al. (2016) fed pigs (25 to 50 kg) Pens of pigs were weighed, and feed disappearance was de - diets with or without 15% soybean hulls, which is a source termined every 2  wk to determine ADG, average daily feed of both soluble and insoluble fibers. Their SID Thr:Lys ratios intake (ADFI), and G:F. Two weeks before the end of the ex- ranged from 45% to 90% of the Lys requirement. Results periment, three pigs per pen were removed and marketed. The from that study showed a quadratic increase in average daily remaining pigs in the pen were weighed and marketed at the gain (ADG) and feed efficiency (gain-to-feed ratio [G:F]) of completion of the experiment. No carcass data were collected pigs fed both low- and high-fiber diets. When combining the because of packing plant restrictions due to COVID-19. broken line and quadratic polynomial models, the estimated Statistical Analysis optimum SID Thr:Lys ratio for ADG was 63% and 66% and for G:F was 61% and 71% for pigs fed low- or high-fiber Data from both barns were combined following a diets, respectively. This compares with a requirement esti- nonsignificant barn × treatment comparison. Pens of pigs mate for SID Thr of 60% of Lys for the pigs in this weight were the experimental units for all data. Data were analyzed range (NRC (2012). It was concluded that, in order to max - using the nlme package of R (Version 4.0.0, R Foundation for imize growth performance, the level of digestible Thr may Statistical Computing, Vienna, Austria) as a randomized com - need to be increased in diets containing soybean hulls as a plete block design with BW as the blocking factor and pen as source of fiber. However, it is unclear if increased Thr is also the experimental unit. The main effects and interactions of needed when diets contain DDGS as opposed to soybean DDGS and Thr level were tested. Model assumptions were hulls. Therefore, the objective of the study herein was to test checked and considered to be appropriately met. Differences whether high levels of DDGS, as an insoluble fiber source, between treatments were considered significant at P ≤ 0.05. increased the Thr:Lys ratio needed to maximize the growth performance of finishing pigs. RESULTS There were no interactions observed between SID Thr:Lys ratio MATERIALS AND METHODS and DDGS for any response criteria (Table 3). Furthermore, The Kansas State University Institutional Animal Care and no differences were detected (P > 0.10) for ADG, ADFI, G:F or Use Committee approved the protocol used in this experiment. BW for pigs fed diets at the normal Thr:Lys ratios compared with pigs fed high Thr:Lys ratio throughout the study. Animals and Diets From day 0 to 56, pigs fed diets without DDGS had increased This experiment was conducted in two barns at a commercial (P < 0.001) ADG, increased day 56 BW, and improved research grow-finishing site in southwest Minnesota (New (P < 0.001) G:F compared with pigs fed diets without DDGS Horizon Farms, Pipestone, MN). Each barn was naturally (Table 4). Interestingly, from day 56 to 112, pigs fed DDGS ventilated and double-curtain-sided with a slatted concrete had increased (P = 0.019) ADG compared with pigs fed diets floor and deep manure storage. Each pen (3.05 × 5.49 m) was without DDGS, which could be explained by the reduction in equipped with a 5-hole stainless steel dry self-feeder (Thorp DDGS level from 40% to 30% and 15% in the third and fourth Equipment, Thorp, WI) and a cup waterer for ad libitum ac - dietary phases, respectively. Pigs fed diets without DDGS had cess to feed and water. The facility was equipped with a com - decreased (P = 0.004) ADFI and improved (P = 0.004) G:F puterized feeding system (FeedPro; Feedlogic Corp., Willmar, compared with those pigs fed diets with DDGS. MN) that delivered and recorded daily feed additions. Overall (day 0 to 112), pigs fed diets without DDGS had Two groups of 1,080 pigs (2,160 total pigs; PIC increased (P < 0.001) ADG and BW, reduced ( P < 0.001) 337  ×  1,050; initially 35.1  ±  0.5  kg) were used in a 112-d ADFI, and improved (P < 0.001) G:F compared with pigs that growth trial. The two groups of pigs were started in two were fed diets with DDGS. identical barns at the same initial weight and approximately 1 mo apart. In both barns, pens of pigs (27 pigs per pen) DISCUSSION were randomly assigned to one of four dietary treatments in a randomized complete block design with BW serving as the The fiber content of a feed ingredient is normally measured blocking factor resulting in 20 observations (pens) per treat - using various methods, which include crude fiber, neutral de - ment. Dietary treatments were arranged in a 2 × 2 factorial tergent fiber, acid detergent fiber, and total dietary fiber (TDF). with main effects of SID Thr:Lys ratio (normal vs. high) and The total dietary fiber includes insoluble dietary fiber and sol - DDGS (without or with). Diets were fed in four phases from uble dietary fiber and is designed to characterize types of in- 34 to 57, 57 to 79, 79 to 104, and 104 to 130 kg BW (Tables digestible carbohydrates in feedstuffs (Kerr et al., 2013). Corn 1 and 2). Diets with DDGS were formulated to contain 40% DDGS is predominantly considered an insoluble fiber source DDGS in phases 1 and 2, 30% in phase 3, and 15% in phase because most of the TDF in DDGS is insoluble, ranging from 4. The diets with normal Thr level were formulated to meet 31.8% to 37.3%, whereas the soluble fiber component ranges the NRC’s (2012) requirement estimates and contained SID from 0.0% to 1.8% (Urriola et al., 2010). The high insoluble Thr:Lys ratios of 61%, 62%, 63%, and 65%, whereas the fiber content of corn DDGS may influence not only pig per - high Thr diets had SID Thr:Lys ratios of 67%, 68%, 69%, formance but also intestinal health. Insoluble fibers can act and 72%, for the four dietary phases, respectively. Diets were in the intestinal tract by increasing water holding capacity, formulated using NRC (2012) ingredient amino acid (AA) which increases digesta viscosity and increases fecal bulki- values and SID coefficients. All treatment diets were manu - ness as well as digesta passage rate ( McRorie and McKeown, factured at New Horizon Farms Feed Mill in Pipestone, MN, 2017). In addition, mucus in the intestinal tract of pigs is and were formulated to meet or exceed NRC (2012) require- characterized by its high level of serine, proline, and particu - ment estimates for growing-finishing pigs for their respective larly Thr (Święch et al., 2019 ). Mucins form intestinal mucus, weight ranges. are secreted by goblet cells, and are resistant to digestion Fiber and threonine in finishing pig diets 3 Table 1. Composition of phases 1 and 2 diets (as-fed basis) Phase 1 Phase 2 No DDGS DDGS No DDGS DDGS Item Normal Thr High Thr Normal Thr High Thr Normal Thr High Thr Normal Thr High Thr Ingredients, % Corn 72.67 72.60 50.34 50.27 78.90 78.84 55.75 55.70 Soybean meal 24.64 24.65 6.82 6.82 18.51 18.51 1.49 1.49 Corn DDGS — — 40.00 40.00 — — 40.00 40.00 Limestone 0.95 0.95 1.35 1.35 0.95 0.95 1.35 1.35 Monocalcium P (21% P) 0.60 0.60 — — 0.55 0.55 — — Salt 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 l-Lys-HCl 0.30 0.30 0.60 0.60 0.30 0.30 0.58 0.58 dl-Met 0.08 0.08 0.03 0.03 0.05 0.05 — — l-Thr 0.08 0.14 0.12 0.19 0.08 0.13 0.11 0.17 l-Trp 0.01 0.01 0.07 0.07 0.02 0.02 0.07 0.07 Mineral–vitamin premix 0.15 0.15 0.15 0.15 0.13 0.13 0.13 0.13 || Phytase 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 Total 100 100 100 100 100 100 100 100 Calculated analysis SID amino acids, % Lys 1.02 1.02 1.02 1.02 0.87 0.87 0.87 0.87 Ile:Lys 62 62 55 55 61 61 55 55 Leu:Lys 136 136 169 169 144 143 184 184 Met:Lys 33 33 32 32 32 32 32 32 Met and Cys:Lys 58 58 58 58 58 58 60 60 Thr:Lys 61 67 61 67 62 68 62 68 Trp:Lys 19.1 19.1 19.1 19.1 19.1 19.1 19.1 19.1 Val:Lys 69 69 69 69 70 70 71 71 SID Lys:NE, g/Mcal 4.13 4.13 4.14 4.14 3.47 3.47 3.49 3.49 NE, kcal/kg 2,472 2,472 2,461 2,461 2,509 2,509 2,492 2,494 CP, % 18.14 18.19 19.39 19.43 15.72 15.76 17.25 17.28 Ca, % 0.58 0.58 0.61 0.61 0.55 0.55 0.59 0.59 P, % 0.49 0.49 0.47 0.47 0.46 0.45 0.45 0.45 STTD P, % 0.37 0.37 0.37 0.37 0.35 0.35 0.36 0.36 NDF, % 8.64 8.64 18.55 18.54 8.71 8.70 18.60 18.60 IDF, % 11.90 11.89 20.28 20.28 11.54 11.54 19.97 19.97 IDF, insoluble dietary fiber; NDF, neutral detergent fiber; STTD, standard total tract digestibility. Phases 1 and 2 were fed from 34.9 to 57.4, and 57.4 to 82.5 kg, respectively. Provided per kilogram of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, and 11 µg vitamin B12. || Optiphos 2000 (Huvepharma Inc. Peachtree City, GA) provided 858.7 units of phytase/kg of diet with an assumed release of 0.12% STTD P. Insoluble digestible fiber. Matrix loading values are derived from Navarro (2018). (Święch et al., 2019). Consequently, an increase in goblet cell fatty acid production, which is important in modulating im - numbers in the villi or crypts may result in an increase in in - munological response and in maintaining intestinal function testinal mucus and, therefore, greater ileal endogenous losses (Neis et al., 2015; Tang et al., 2021; Zhang et al., 2016). of Thr (Święch et al., 2019). Furthermore, studies in fish have reported that dietary Thr Schaart et al. (2005) observed that 40% to 60% of dietary deficiency reduces the activity of intestinal enzymes, such as Thr was absorbed by the portal-drained viscera in the pig. In trypsin, alpha-amylase, chymotrypsin, and lipase ( Hong et addition, Law et al. (2007) observed that dietary deficiency al., 2015). Thus, Thr appears to be involved in significant of Thr reduced the number of goblet cells and mucin con - roles, including intestinal barrier function, immune response, tent in the small intestine, which was not restored by intra- and absorptive capacity. As the pig grows, the requirement venous administration of Thr, concluding that the intestinal for amino acids that are used for maintenance, such as Thr, tract of the pig uses considerable amounts of Thr from the increases, and the NRC (2012) estimates that the dietary re- lumen rather than from arterial blood. Degradation of Thr quirement for SID Thr is 60% to 65% of SID Lys for pigs by gut bacteria from the Clostridium family results in volatile from 25 to 135 kg BW. However, research suggests that these 4 Tolosa et al. Table 2. Composition of phases 3 and 4 diets (as-fed basis) Phase 3 Phase 4 No DDGS DDGS No DDGS DDGS Item Normal Thr High Thr Normal Thr High Thr Normal Thr High Thr Normal Thr High Thr Ingredients, % Corn 83.54 83.49 66.02 65.97 85.82 85.77 77.09 77.04 Soybean meal 14.01 14.01 1.44 1.45 11.95 11.95 5.67 5.67 Corn DDGS — — 30.00 30.00 — — 15.00 15.00 Limestone 0.95 0.95 1.25 1.25 0.90 0.90 1.05 1.05 Monocalcium P (21% P) 0.45 0.45 — — 0.25 0.25 — — Salt 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 l-Lys-HCl 0.30 0.30 0.50 0.50 0.30 0.30 0.40 0.40 dl-Met 0.03 0.03 — — 0.02 0.02 — — l-Thr 0.08 0.13 0.10 0.15 0.09 0.14 0.10 0.15 l-Trp 0.02 0.02 0.06 0.06 0.02 0.02 0.04 0.04 Mineral–vitamin premix 0.10 0.10 0.10 0.10 0.08 0.08 0.08 0.08 || Phytase 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 Total 100 100 100 100 100 100 100 100 Calculated analysis SID amino acids, % Lys 0.76 0.76 0.76 0.76 0.71 0.71 0.71 0.71 Ile:Lys 60 60 55 55 60 60 57 57 Leu:Lys 151 150 186 186 155 155 173 173 Met:Lys 31 31 32 32 30 30 31 31 Met and Cys:Lys 58 58 62 62 58 58 60 60 Thr:Lys 63 69 63 69 65 72 65 72 Trp:Lys 19.2 19.2 19.1 19.1 19.0 19.0 19.1 19.1 Val:Lys 70 70 72 72 70 70 71 71 SID Lys:NE, g/Mcal 2.99 2.99 3.01 3.01 2.78 2.78 2.78 2.78 NE, kcal/kg 2,540 2,540 2,527 2,527 2,558 2,558 2,551 2,551 CP, % 13.94 13.98 15.17 15.20 13.15 13.19 13.76 13.80 Ca, % 0.52 0.52 0.54 0.54 0.45 0.45 0.46 0.46 P, % 0.41 0.41 0.40 0.40 0.36 0.36 0.35 0.35 STTD P, % 0.32 0.32 0.32 0.32 0.28 0.28 0.27 0.27 NDF, % 8.76 8.76 16.18 16.18 8.80 8.79 12.51 12.51 IDF, % 11.29 11.28 17.63 17.62 11.19 11.18 14.36 14.36 IDF, insoluble dietary fiber; NDF, neutral detergent fiber; STTD, standard total tract digestibility. Phases 3 and 4 were fed from 82.5 to 108.2, and 108.2 kg to market, respectively. Provided per kilogram of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, and 11 µg vitamin B12. || Optiphos 2000 (Huvepharma Inc. Peachtree City, GA) provided 858.7 units of phytase/kg of diet with an assumed release of 0.12% STTD P. Insoluble digestible fiber. Matrix loading values are derived from Navarro (2018). minimum requirement estimates may change depending on ADG when feeding a low-fibrous diet compared with a high- ingredients used in diet formulation, especially ingredients af - fibrous diet increased from 76% to 80% SID Thr:Lys ratio. fecting the fiber content of the diet (Zhu et al., 2005). Using Mathai et al. (2016) quadratic equation, the increase While data from the current study did not show an in - in gain when going from 76% to 80% SID Thr:Lys ratio fluence of increasing the SID Thr:Lys ratio on pig perfor - resulted in 1.8 g/d improved gain. Over a 112-d period, this mance, Mathai et al. (2016) observed improved performance would result in a 202-g heavier pig. Even though the findings of growing pigs when increased SID Thr:Lys ratio was in- suggested an increase in the requirement, the response was cluded in high-fiber diets compared with pigs fed a low-fiber small and almost impossible to measure. Furthermore, Zhu diet. The diets used were formulated to contain high and et al. (2005) fed growing pigs increasing levels of dietary low fibers by including soybean hulls (15% or 0% soybean pectin from 0% to 12% and an additional treatment that hulls, respectively), which is both an insoluble and soluble provided 8% cellulose. A linear decrease in ileal digestible fiber source. Mathai et al. (2016) included 45%, 54%, 63%, Thr utilization for protein deposition was observed as pectin 72%, 81%, and 90% SID Thr:Lys ratios for pigs from 25 increased in the diet; however, the cellulose level of the diet to 50 kg BW. The quadratic curve estimation for maximum did not influence the utilization of Thr, suggesting that fiber Fiber and threonine in finishing pig diets 5 Table 3. Interactive effects of DDGS and Thr on grow-finish pig performance Item No DDGS DDGS SEM P = || $ || $ Normal Thr High Thr Normal Thr High Thr Thr × DDGS Thr DDGS Initial BW, kg Day 0 35.1 35.1 35.1 34.9 0.47 0.384 0.503 0.259 Day 56 84.1 84.8 80.9 80.5 0.67 0.222 0.755 <0.001 Day 112 136.6 136.9 133.6 133.3 0.80 0.655 0.972 <0.001 Day 0 to 56 ADG, kg 0.90 0.90 0.84 0.84 0.011 0.635 0.986 <0.001 ADFI, kg 2.10 2.14 2.18 2.15 0.029 0.168 0.651 0.081 G:F 0.429 0.421 0.387 0.389 0.0039 0.133 0.379 <0.001 Day 56 to 112 ADG, kg 0.94 0.94 0.96 0.97 0.016 0.597 0.926 0.019 ADFI, kg 3.12 3.15 3.29 3.29 0.044 0.488 0.572 0.004 G:F 0.304 0.299 0.292 0.293 0.0037 0.294 0.547 0.004 Day 0 to 112 ADG, kg 0.92 0.92 0.89 0.89 0.006 0.989 0.973 <0.001 ADFI, kg 2.59 2.64 2.72 2.71 0.027 0.252 0.556 <0.001 G:F 0.356 0.350 0.331 0.332 0.0030 0.164 0.408 <0.001 A total of 2,160 pigs were used in two groups with 27 pigs per pen and 10 replicates per treatment. Phase 1 was fed from day 0 to 28, phase 2 from day 28 to 56, phase 3 from day 56 to 84, and phase 4 from day 84 to 112. DDGS included at 40% in phases 1 and 2, 30% in phase 3, and 15% in phase 4. || SID Thr:Lys was 61%, 62%, 63%, and 65% in phases 1, 2, 3, and 4, respectively. SID Thr:Lys was 67%, 68%, 69%, and 72% in phases 1, 2, 3, and 4, respectively. Table 4. Main effects of DDGS and Thr on grow-finish pig performance DDGS SEM P = Thr SEM P = || $ No DDGS High DDGS Normal Thr High Thr Initial BW, lb Day 0 35.1 34.9 0.46 0.259 35.1 35.0 0.46 0.503 Day 56 84.4 80.7 0.59 <0.001 82.5 82.6 0.59 0.755 Day 112 136.7 133.4 0.63 <0.001 135.1 135.1 0.63 0.972 Day 0 to 56 ADG, l kg 0.90 0.84 0.010 <0.001 0.87 0.87 0.010 0.986 ADFI, kg 2.12 2.16 0.023 0.081 2.14 2.15 0.023 0.651 G:F 0.425 0.388 0.0032 <0.001 0.408 0.405 0.0032 0.379 Day 56 to 112 ADG, kg 0.95 0.96 0.014 0.019 0.96 0.95 0.014 0.926 ADFI, kg 3.14 3.29 0.038 <0.001 3.21 3.22 0.038 0.572 G:F 0.302 0.293 0.0029 0.004 0.298 0.296 0.0029 0.547 Day 0 to 112 ADG, kg 0.92 0.89 0.004 <0.001 0.91 0.91 0.004 0.973 ADFI, kg 2.61 2.71 0.019 <0.001 2.66 2.67 0.019 0.556 G:F 0.353 0.332 0.0024 <0.001 0.343 0.341 0.0024 0.408 A total of 2,160 pigs were used in two groups with 27 pigs per pen and 10 replicates per treatment. Phase 1 was fed from day 0 to 28, phase 2 from day 28 to 56, phase 3 from day 56 to 84, and phase 4 from day 84 to 112. DDGS included at 40% in phases 1 and 2, 30% in phase 3, and 15% in phase 4. || SID Thr:Lys was 61%, 6%2, 63%, and 65% in phases 1, 2, 3, and 4, respectively. SID Thr:Lys was 67%, 68%, 69%, and 72% in phases 1, 2, 3, and 4, respectively. type may have an impact on the Thr requirement. Soluble decreased with no ameliorating effect of increasing digest - fiber includes pectins, gums, and β-glucans, whereas in- ible Thr. Therefore, this presents the possibility that the soluble fiber includes cellulose and hemicellulose (Jha and greater insoluble fiber content of DDGS may not result in Berrocoso, 2015). In the current study, only DDGS (a source an increased need for digestible Thr:Lys ratio above the pigs’ of insoluble fiber) was used in the diet, and pig performance current estimated requirement. 6 Tolosa et al. Kerr, B. J., W. A. Dozier III, and G. C. Shurson. 2013. Effects of reduced- The current study corroborated that the high inclusion (i.e., oil corn distillers dried grains with solubles composition on digesti - 40%) of corn co-products, such as DDGS, which is used in ble and metabolizable energy value and prediction in growing pigs. grow-finishing diets at the expense of corn and soybean meal, J. Anim. Sci. 91:3231–3243. doi:10.2527/jas.2013-6252 negatively impacts growth performance. Hardman (2013) Law, G. K., R. F. Bertolo, A. Adjiri-Awere, P. B. Pencharz, and R. O. observed that increasing DDGS inclusion from 0% to 40% Ball.2007. Adequate oral threonine is critical for mucin pro - in the diet for grow-finish pigs from 23 to 128  kg linearly duction and gut function in neonatal piglets.Am. J. Physiol. reduced ADG and resulted in a 1.4-kg reduction in weight Gastrointest. Liver Physiol. 292:G1293–G1301. doi:10.1152/ after 120 d compared with pigs fed the diet without DDGS. ajpgi.00221.2006 A cooperative study by Cromwell et al. (2011) included 560 Le Flocʹh, N., and B. Sève. 2005. Catabolism through the threonine pigs from nine university research stations and fed pigs from dehydrogenase pathway does not account for the high first-pass extraction rate of dietary threonine by the portal drained viscera in 32 to 120 kg diets with increasing levels of DDGS from 0% pigs. Br. J. Nutr. 93:447–456. doi:10.1079/bjn20051375 to 45% resulting in a linear decrease in ADG and in a 3-kg Mathai, J. K., J. K. Htoo, J. E. Thomson, K. J. Touchette, and H. H. reduction in final BW. These results are in agreement with the Stein. 2016. Effects of dietary fiber on the ideal standardized il - current study where feeding a diet with DDGS to pigs from 35 eal digestible threonine:lysine ratio for twenty-five to fifty kilogram to 136 kg decreased gain and feed efficiency, and reduced final growing gilts. J. Anim. Sci. 94:4217–4230. doi:10.2527/jas.2016- BW by 3.2 kg compared with pigs fed diets without DDGS. We speculate that the bulkiness of the 40% DDGS diets may McRorie, J. W. Jr, and N. M. McKeown. 2017. Understanding the have limited feed intake by gut fill in the early portions of the physics of functional fibers in the gastrointestinal tract: an evi - study. But then, as DDGS levels decreased, pigs were able to dence-based approach to resolving enduring misconceptions a - consume more feed resulting in increased ADG in late fin- bout insoluble and soluble fiber.J . Acad. Nutr. Diet. 117:251–264. doi:10.1016/j.jand.2016.09.021 ishing. However, this almost compensatory growth effect was Montagne, L., J. R. Pluske, and D. J. Hampson. 2003. A review of not of a magnitude to offset the poor performance early in interactions between dietary fibre and the intestinal mucosa, and the study and resulted in a 3-kg decrease in the final weight. their consequences on digestive health in young non-ruminant an - In conclusion, the current study demonstrated that feeding imals. Anim. Feed Sci. Technol. 108:95–117. doi:10.1016/S0377- diets with high levels of insoluble fiber from DDGS decreased 8401(03)00163-9 growth performance. In this study, increasing the digestible Myrie, S. B., R. F. P. Bertolo, W. C. Sauer, and R. O. Ball. 2003. Threo- Thr concentration in DDGS-containing diets did not im - nine retention is reduced in diets that increase mucin production in prove growth performance. Further research should explore pigs. Proceedings of the 9th International Symposium on Digestive whether fiber type influences the SID Thr:Lys ratio require - Physiology in Pigs. Volume 2: Short Communications; AB, Canada. ment of growing and finishing pigs. University of Alberta, Edmonton, AB. p. 250–252. Navarro, D. M. D. L. 2018. Influence of physicochemical characteristics and inclusion rate of fiber-rich ingredients on utilization of dietary Acknowledgments fiber and energy by growing pigs [doctoral thesis]. University of Illinois at Urbana-Champaign, IL. We would like to thank the team at New Horizon Farms, Neis, E. P., C. H. Dejong, and S. S. Rensen. 2015. The role of microbial Pipestone, MN, for providing the animals and technical sup - amino acid metabolism in host metabolism.Nutrients . 7:2930– port for this project. The contribution no. is 22-250-J from 2946. doi:10.3390/nu7042930. the Kansas Agricultural Station, Manhattan, KS. NRC. 2012. Nutrient requirements of swine. 11th rev. ed. Natl. Acad. Press, Washington, DC. Schaart, M. W., H. Schierbeek, S. R. van der Schoor, B. Stoll, D. G. Conflict of interest statement Burrin, P. J. Reeds, and J. B. van Goudoever. 2005. Threonine u- The authors declare no conflicts of interest. tilization is high in the intestine of piglets.J . Nutr. 135:765–770. doi:10.1093/jn/135.4.765 Święch, E., A. Tuśnio, M. Barszcz, M. Taciak, and E. Siwiak. 2019. LITERATURE CITED Goblet cells and mucus layer in the gut of young pigs: response to dietary contents of threonine and non-essential amino acids. Cromwell, G. L., M. J. Azain, O. Adeola, S. K. Baidoo, S. D. Carter, T. J. Anim. Physiol. Anim. Nutr. (Berl). 103:894–905. doi:10.1111/ D. Crenshaw, S. W. Kim, D. C. Mahan, P. S. Miller, and M. C. Shan - jpn.13086 non. 2011. Corn distillers dried grains with solubles in diets for Tang, Q., P. Tan, N. Ma, and X. Ma. 2021. Physiological functions growing-finishing pigs: a cooperative study. J. Anim. Sci. 89:2801– of threonine in animals: beyond nutrition metabolism.Nutrients . 2811. doi:10.2527/jas.2010-3704 13:2592. doi:10.3390/nu13082592 Dilger, R. N., J. S. Sands, D. Ragland, and O. Adeola. 2004. Digestibility Urriola, P. E., G. C. Shurson, and H. H. Stein.2010. Digestibility of die - of nitrogen and amino acids in soybean meal with added soyhulls. tary fiber in distillers co-products fed to growing pigs. J. Anim. Sci. J. Anim. Sci. 82:715–724. doi:10.2527/2004.823715x 88:2373–2381. doi:10.2527/jas.2009-2227 Hardman, S. J. 2013. Effect of dietary distillers dried grains with solubles Wang, T. C., and M. F. Fuller. 1989. The optimum dietary amino acid (DDGS) and pig removal strategy at harvest on the growth perfor- pattern for growing pigs. Br. J. Nutr. 62:77–89. doi:10.1079/ mance, carcass characteristics, and fat quality of growing-finishing bjn19890009 pigs [M.S. thesis]. University of Illinois at Urbana-Champaign, IL. Zhang, Q., X. Chen, S. Eicher, K. Ajuwon, and T. Applegate. 2016. Hong, Y., W. Jiang, S. Kuang, K. Hu, L. Tang, Y. Liu, J. Jiang, Y. Zhang, Effect of threonine deficiency on intestinal integrity and immune X. Zhou, and L. Feng. 2015. Growth, digestive and absorptive ca- response to feed withdrawal combined with coccidial vaccine chal - pacity and antioxidant status in intestine and hepatopancreas of lenge in broiler chicks. Br. J. Nutr. 116:2030–2043. doi:10.1017/ sub-adult grass carp Ctenopharyngodonidella fed graded levels of S0007114516003238 dietary threonine. J. Anim. Sci. Biotechnol. 6:1–11. doi:10.1186/ Zhu, C. L., M. Rademacher, and C. F. M. de Lange. 2005. Increasing s40104-015-0032-1 dietary pectin level reduces utilization of digestible threonine in - Jha, R., and J. D. Berrocoso. 2015. Review: Dietary fiber utilization and take, but not lysine intake, for body protein deposition in growing its effects on physiological functions and gut health of swine. Ani - pigs. J. Anim. Sci. 83:1044–1053. doi:10.2527/2005.8351044x mal. 9:1441–1452. doi:10.1017/S1751731115000919 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Translational Animal Science Oxford University Press

Evaluation of increasing digestible threonine to lysine ratio in corn–soybean meal diets without and with distillers dried grains with solubles on growth performance of growing-finishing pigs

Translational Animal Science , Volume 6 (2): 1 – May 6, 2022

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Translational Animal Science, 2022, 6, 1–6 https://doi.org/10.1093/tas/txac058 Advance access publication 6 May 2022 Non Ruminant Nutrition Evaluation of increasing digestible threonine to lysine ratio in corn–soybean meal diets without and with distillers dried grains with solubles on growth performance of growing-finishing pigs † † †,1 †, Andres F. Tolosa, Mike D. Tokach, Robert D. Goodband, Jason C. Woodworth, † ‡, Joel M. DeRouchey, and Jordan T. Gebhardt Department of Animal Sciences and Industry, College of Agriculture, Kansas State University, Manhattan, KS 66506-0201, USA Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506-0201, USA Corresponding author: Goodband@ksu.edu ABSTRACT Corn distillers dried grains with solubles (DDGS) is commonly available and often can lower diet cost for swine diets. This corn co-product is recognized to be a source of dietary insoluble fiber, which can not only increase the villous length of the gut mucosa but also increase intestinal production of mucin. Mucin structure, functions, and synthesis are correlated to Thr intake; consequently, the dietary Thr level may need to be increased when feeding an insoluble fiber source such as corn–DDGS. Thus, the objective of this study was to evaluate if feeding standardized ileal digestible (SID) Thr:Lys ratio at or above the estimated requirement in diets without and with DDGS would influence growth performance in finishing pigs. A total of 2,160 pigs (PIC 337 × 1,050; initially 35.1 ± 0.5 kg) were used in a 112-d growth trial. Pigs were randomly assigned to pens (27 pigs per pen) in a randomized complete block design by body weight (BW) with 20 replications per treatment. Pens of pigs were allotted to one of four dietary treatments that were arranged in a 2 × 2 factorial with main effects of dietary Thr level (normal vs. high) and DDGS (without or with). Treatment diets were formulated in four phases from 34 to 57, 57 to 79, 79 to 104, and 104 to 130 kg BW. Diets with high DDGS were formulated to include 40% DDGS in phases 1 and 2, 30% in phase 3, and 15% in phase 4. The normal Thr diets were formulated to contain 61%, 62%, 63%, and 65% SID Thr:Lys ratios for the four dietary phases, respectively. High Thr diets had SID Thr:Lys ratios of 67%, 68%, 69%, and 72%, respectively. There were no interactions (P > 0.10) observed in any phase or overall between Thr level and added DDGS. For the overall period (day 0 to 112), pigs fed diets without DDGS had increased (P < 0.001) average daily gain (ADG) but reduced (P < 0.001) average daily feed intake (ADFI), leading to increased (P < 0.001) feed efficiency (gain-to-feed ratio [G:F]). There was no evidence for difference ( P > 0.10) between pigs fed diets formulated at normal or high SID Thr:Lys ratio. In summary, feeding high levels of DDGS decreased ADG and increased ADFI, which resulted in decreased G:F and lower final BW, regardless of the dietary SID Thr:Lys ratio level. In the current study, increasing the level of digestible Thr in a diet that contained a highly insoluble fiber source did not increase the growth performance of grow-finish pigs. Key words: DDGS, grow-finish pigs, growth, insoluble fiber, threonine INTRODUCTION pig. The NRC (2012) suggests that the dietary requirement for standardized ileal digestible (SID) Thr is 60% to 65% Early research by Wang and Fuller (1989) categorized Thr as of that of SID Lys for pigs from 25 to 135  kg body weight the first limiting amino acid for maintenance, which suggests (BW). However, these minimum requirements may change that the utilization of Thr for protein deposition is less than depending on diet formulation and fiber type of the diet (Zhu that for other body needs. The primary reason for this may et al., 2005). be the extensive use of Thr by splanchnic tissues, resulting Furthermore, the abundant availability and lower cost of in some inefficiency of Thr conversion to body protein and corn distillers dried grains with solubles (DDGS) have allowed greater utilization of Thr by intestinal tissue ( Le Flocʹh and nutritionists to partially replace corn, soybean meal, and sup - Seve, 2005). These authors noted that labeled enrichments plemental phosphorus, reducing diet cost for grow-finish pigs. of Thr-bound protein were quite high in the pancreas and However, high concentrations of insoluble fiber in DDGS re - the mucosa compared with that of the liver, which led to the sult in an increased passage rate of chyme and increased en - conclusion that Thr incorporation in mucosa protein and the dogenous losses of digestive enzymes, enterocytes, and mucin pancreas would be very important ( Le Flocʹh and Seve, 2005 ). (Dilger et al., 2004). Therefore, greater inclusion of DDGS in Similarly,Myrie et al. (2003) suggested that an increase in diets may potentially influence mucin secretion and secretion, mucin production reduced body Thr retention. As intestinal which, in part, may impact gastrointestinal epithelial cells,- di tissue increases in size as the pig grows, mucin production gestive enzymes, and mucosal secretions of which Thr is a could increase, and thus, the requirement for Thr would also major component (Montagne et al., 2003). increase to support the intestinal tract and growth of the Received March 2, 2022 Accepted May 3, 2022. Published by Oxford University Press on behalf of the American Society of Animal Science 2022. This work is written by (a) US Government employee(s) and is in the public domain in the US. 2 Tolosa et al. In a recent study, Mathai et al. (2016) fed pigs (25 to 50 kg) Pens of pigs were weighed, and feed disappearance was de - diets with or without 15% soybean hulls, which is a source termined every 2  wk to determine ADG, average daily feed of both soluble and insoluble fibers. Their SID Thr:Lys ratios intake (ADFI), and G:F. Two weeks before the end of the ex- ranged from 45% to 90% of the Lys requirement. Results periment, three pigs per pen were removed and marketed. The from that study showed a quadratic increase in average daily remaining pigs in the pen were weighed and marketed at the gain (ADG) and feed efficiency (gain-to-feed ratio [G:F]) of completion of the experiment. No carcass data were collected pigs fed both low- and high-fiber diets. When combining the because of packing plant restrictions due to COVID-19. broken line and quadratic polynomial models, the estimated Statistical Analysis optimum SID Thr:Lys ratio for ADG was 63% and 66% and for G:F was 61% and 71% for pigs fed low- or high-fiber Data from both barns were combined following a diets, respectively. This compares with a requirement esti- nonsignificant barn × treatment comparison. Pens of pigs mate for SID Thr of 60% of Lys for the pigs in this weight were the experimental units for all data. Data were analyzed range (NRC (2012). It was concluded that, in order to max - using the nlme package of R (Version 4.0.0, R Foundation for imize growth performance, the level of digestible Thr may Statistical Computing, Vienna, Austria) as a randomized com - need to be increased in diets containing soybean hulls as a plete block design with BW as the blocking factor and pen as source of fiber. However, it is unclear if increased Thr is also the experimental unit. The main effects and interactions of needed when diets contain DDGS as opposed to soybean DDGS and Thr level were tested. Model assumptions were hulls. Therefore, the objective of the study herein was to test checked and considered to be appropriately met. Differences whether high levels of DDGS, as an insoluble fiber source, between treatments were considered significant at P ≤ 0.05. increased the Thr:Lys ratio needed to maximize the growth performance of finishing pigs. RESULTS There were no interactions observed between SID Thr:Lys ratio MATERIALS AND METHODS and DDGS for any response criteria (Table 3). Furthermore, The Kansas State University Institutional Animal Care and no differences were detected (P > 0.10) for ADG, ADFI, G:F or Use Committee approved the protocol used in this experiment. BW for pigs fed diets at the normal Thr:Lys ratios compared with pigs fed high Thr:Lys ratio throughout the study. Animals and Diets From day 0 to 56, pigs fed diets without DDGS had increased This experiment was conducted in two barns at a commercial (P < 0.001) ADG, increased day 56 BW, and improved research grow-finishing site in southwest Minnesota (New (P < 0.001) G:F compared with pigs fed diets without DDGS Horizon Farms, Pipestone, MN). Each barn was naturally (Table 4). Interestingly, from day 56 to 112, pigs fed DDGS ventilated and double-curtain-sided with a slatted concrete had increased (P = 0.019) ADG compared with pigs fed diets floor and deep manure storage. Each pen (3.05 × 5.49 m) was without DDGS, which could be explained by the reduction in equipped with a 5-hole stainless steel dry self-feeder (Thorp DDGS level from 40% to 30% and 15% in the third and fourth Equipment, Thorp, WI) and a cup waterer for ad libitum ac - dietary phases, respectively. Pigs fed diets without DDGS had cess to feed and water. The facility was equipped with a com - decreased (P = 0.004) ADFI and improved (P = 0.004) G:F puterized feeding system (FeedPro; Feedlogic Corp., Willmar, compared with those pigs fed diets with DDGS. MN) that delivered and recorded daily feed additions. Overall (day 0 to 112), pigs fed diets without DDGS had Two groups of 1,080 pigs (2,160 total pigs; PIC increased (P < 0.001) ADG and BW, reduced ( P < 0.001) 337  ×  1,050; initially 35.1  ±  0.5  kg) were used in a 112-d ADFI, and improved (P < 0.001) G:F compared with pigs that growth trial. The two groups of pigs were started in two were fed diets with DDGS. identical barns at the same initial weight and approximately 1 mo apart. In both barns, pens of pigs (27 pigs per pen) DISCUSSION were randomly assigned to one of four dietary treatments in a randomized complete block design with BW serving as the The fiber content of a feed ingredient is normally measured blocking factor resulting in 20 observations (pens) per treat - using various methods, which include crude fiber, neutral de - ment. Dietary treatments were arranged in a 2 × 2 factorial tergent fiber, acid detergent fiber, and total dietary fiber (TDF). with main effects of SID Thr:Lys ratio (normal vs. high) and The total dietary fiber includes insoluble dietary fiber and sol - DDGS (without or with). Diets were fed in four phases from uble dietary fiber and is designed to characterize types of in- 34 to 57, 57 to 79, 79 to 104, and 104 to 130 kg BW (Tables digestible carbohydrates in feedstuffs (Kerr et al., 2013). Corn 1 and 2). Diets with DDGS were formulated to contain 40% DDGS is predominantly considered an insoluble fiber source DDGS in phases 1 and 2, 30% in phase 3, and 15% in phase because most of the TDF in DDGS is insoluble, ranging from 4. The diets with normal Thr level were formulated to meet 31.8% to 37.3%, whereas the soluble fiber component ranges the NRC’s (2012) requirement estimates and contained SID from 0.0% to 1.8% (Urriola et al., 2010). The high insoluble Thr:Lys ratios of 61%, 62%, 63%, and 65%, whereas the fiber content of corn DDGS may influence not only pig per - high Thr diets had SID Thr:Lys ratios of 67%, 68%, 69%, formance but also intestinal health. Insoluble fibers can act and 72%, for the four dietary phases, respectively. Diets were in the intestinal tract by increasing water holding capacity, formulated using NRC (2012) ingredient amino acid (AA) which increases digesta viscosity and increases fecal bulki- values and SID coefficients. All treatment diets were manu - ness as well as digesta passage rate ( McRorie and McKeown, factured at New Horizon Farms Feed Mill in Pipestone, MN, 2017). In addition, mucus in the intestinal tract of pigs is and were formulated to meet or exceed NRC (2012) require- characterized by its high level of serine, proline, and particu - ment estimates for growing-finishing pigs for their respective larly Thr (Święch et al., 2019 ). Mucins form intestinal mucus, weight ranges. are secreted by goblet cells, and are resistant to digestion Fiber and threonine in finishing pig diets 3 Table 1. Composition of phases 1 and 2 diets (as-fed basis) Phase 1 Phase 2 No DDGS DDGS No DDGS DDGS Item Normal Thr High Thr Normal Thr High Thr Normal Thr High Thr Normal Thr High Thr Ingredients, % Corn 72.67 72.60 50.34 50.27 78.90 78.84 55.75 55.70 Soybean meal 24.64 24.65 6.82 6.82 18.51 18.51 1.49 1.49 Corn DDGS — — 40.00 40.00 — — 40.00 40.00 Limestone 0.95 0.95 1.35 1.35 0.95 0.95 1.35 1.35 Monocalcium P (21% P) 0.60 0.60 — — 0.55 0.55 — — Salt 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 l-Lys-HCl 0.30 0.30 0.60 0.60 0.30 0.30 0.58 0.58 dl-Met 0.08 0.08 0.03 0.03 0.05 0.05 — — l-Thr 0.08 0.14 0.12 0.19 0.08 0.13 0.11 0.17 l-Trp 0.01 0.01 0.07 0.07 0.02 0.02 0.07 0.07 Mineral–vitamin premix 0.15 0.15 0.15 0.15 0.13 0.13 0.13 0.13 || Phytase 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 Total 100 100 100 100 100 100 100 100 Calculated analysis SID amino acids, % Lys 1.02 1.02 1.02 1.02 0.87 0.87 0.87 0.87 Ile:Lys 62 62 55 55 61 61 55 55 Leu:Lys 136 136 169 169 144 143 184 184 Met:Lys 33 33 32 32 32 32 32 32 Met and Cys:Lys 58 58 58 58 58 58 60 60 Thr:Lys 61 67 61 67 62 68 62 68 Trp:Lys 19.1 19.1 19.1 19.1 19.1 19.1 19.1 19.1 Val:Lys 69 69 69 69 70 70 71 71 SID Lys:NE, g/Mcal 4.13 4.13 4.14 4.14 3.47 3.47 3.49 3.49 NE, kcal/kg 2,472 2,472 2,461 2,461 2,509 2,509 2,492 2,494 CP, % 18.14 18.19 19.39 19.43 15.72 15.76 17.25 17.28 Ca, % 0.58 0.58 0.61 0.61 0.55 0.55 0.59 0.59 P, % 0.49 0.49 0.47 0.47 0.46 0.45 0.45 0.45 STTD P, % 0.37 0.37 0.37 0.37 0.35 0.35 0.36 0.36 NDF, % 8.64 8.64 18.55 18.54 8.71 8.70 18.60 18.60 IDF, % 11.90 11.89 20.28 20.28 11.54 11.54 19.97 19.97 IDF, insoluble dietary fiber; NDF, neutral detergent fiber; STTD, standard total tract digestibility. Phases 1 and 2 were fed from 34.9 to 57.4, and 57.4 to 82.5 kg, respectively. Provided per kilogram of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, and 11 µg vitamin B12. || Optiphos 2000 (Huvepharma Inc. Peachtree City, GA) provided 858.7 units of phytase/kg of diet with an assumed release of 0.12% STTD P. Insoluble digestible fiber. Matrix loading values are derived from Navarro (2018). (Święch et al., 2019). Consequently, an increase in goblet cell fatty acid production, which is important in modulating im - numbers in the villi or crypts may result in an increase in in - munological response and in maintaining intestinal function testinal mucus and, therefore, greater ileal endogenous losses (Neis et al., 2015; Tang et al., 2021; Zhang et al., 2016). of Thr (Święch et al., 2019). Furthermore, studies in fish have reported that dietary Thr Schaart et al. (2005) observed that 40% to 60% of dietary deficiency reduces the activity of intestinal enzymes, such as Thr was absorbed by the portal-drained viscera in the pig. In trypsin, alpha-amylase, chymotrypsin, and lipase ( Hong et addition, Law et al. (2007) observed that dietary deficiency al., 2015). Thus, Thr appears to be involved in significant of Thr reduced the number of goblet cells and mucin con - roles, including intestinal barrier function, immune response, tent in the small intestine, which was not restored by intra- and absorptive capacity. As the pig grows, the requirement venous administration of Thr, concluding that the intestinal for amino acids that are used for maintenance, such as Thr, tract of the pig uses considerable amounts of Thr from the increases, and the NRC (2012) estimates that the dietary re- lumen rather than from arterial blood. Degradation of Thr quirement for SID Thr is 60% to 65% of SID Lys for pigs by gut bacteria from the Clostridium family results in volatile from 25 to 135 kg BW. However, research suggests that these 4 Tolosa et al. Table 2. Composition of phases 3 and 4 diets (as-fed basis) Phase 3 Phase 4 No DDGS DDGS No DDGS DDGS Item Normal Thr High Thr Normal Thr High Thr Normal Thr High Thr Normal Thr High Thr Ingredients, % Corn 83.54 83.49 66.02 65.97 85.82 85.77 77.09 77.04 Soybean meal 14.01 14.01 1.44 1.45 11.95 11.95 5.67 5.67 Corn DDGS — — 30.00 30.00 — — 15.00 15.00 Limestone 0.95 0.95 1.25 1.25 0.90 0.90 1.05 1.05 Monocalcium P (21% P) 0.45 0.45 — — 0.25 0.25 — — Salt 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 l-Lys-HCl 0.30 0.30 0.50 0.50 0.30 0.30 0.40 0.40 dl-Met 0.03 0.03 — — 0.02 0.02 — — l-Thr 0.08 0.13 0.10 0.15 0.09 0.14 0.10 0.15 l-Trp 0.02 0.02 0.06 0.06 0.02 0.02 0.04 0.04 Mineral–vitamin premix 0.10 0.10 0.10 0.10 0.08 0.08 0.08 0.08 || Phytase 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 Total 100 100 100 100 100 100 100 100 Calculated analysis SID amino acids, % Lys 0.76 0.76 0.76 0.76 0.71 0.71 0.71 0.71 Ile:Lys 60 60 55 55 60 60 57 57 Leu:Lys 151 150 186 186 155 155 173 173 Met:Lys 31 31 32 32 30 30 31 31 Met and Cys:Lys 58 58 62 62 58 58 60 60 Thr:Lys 63 69 63 69 65 72 65 72 Trp:Lys 19.2 19.2 19.1 19.1 19.0 19.0 19.1 19.1 Val:Lys 70 70 72 72 70 70 71 71 SID Lys:NE, g/Mcal 2.99 2.99 3.01 3.01 2.78 2.78 2.78 2.78 NE, kcal/kg 2,540 2,540 2,527 2,527 2,558 2,558 2,551 2,551 CP, % 13.94 13.98 15.17 15.20 13.15 13.19 13.76 13.80 Ca, % 0.52 0.52 0.54 0.54 0.45 0.45 0.46 0.46 P, % 0.41 0.41 0.40 0.40 0.36 0.36 0.35 0.35 STTD P, % 0.32 0.32 0.32 0.32 0.28 0.28 0.27 0.27 NDF, % 8.76 8.76 16.18 16.18 8.80 8.79 12.51 12.51 IDF, % 11.29 11.28 17.63 17.62 11.19 11.18 14.36 14.36 IDF, insoluble dietary fiber; NDF, neutral detergent fiber; STTD, standard total tract digestibility. Phases 3 and 4 were fed from 82.5 to 108.2, and 108.2 kg to market, respectively. Provided per kilogram of diet: 110 mg Zn, 110 mg Fe, 0.30 mg I, 0.30 mg Se, 5,290 IU vitamin A, 1,323 IU vitamin D, 26.5 IU vitamin E, 1.2 mg vitamin K, 22.5 mg niacin, 7.5 mg pantothenic acid, 2.25 mg riboflavin, and 11 µg vitamin B12. || Optiphos 2000 (Huvepharma Inc. Peachtree City, GA) provided 858.7 units of phytase/kg of diet with an assumed release of 0.12% STTD P. Insoluble digestible fiber. Matrix loading values are derived from Navarro (2018). minimum requirement estimates may change depending on ADG when feeding a low-fibrous diet compared with a high- ingredients used in diet formulation, especially ingredients af - fibrous diet increased from 76% to 80% SID Thr:Lys ratio. fecting the fiber content of the diet (Zhu et al., 2005). Using Mathai et al. (2016) quadratic equation, the increase While data from the current study did not show an in - in gain when going from 76% to 80% SID Thr:Lys ratio fluence of increasing the SID Thr:Lys ratio on pig perfor - resulted in 1.8 g/d improved gain. Over a 112-d period, this mance, Mathai et al. (2016) observed improved performance would result in a 202-g heavier pig. Even though the findings of growing pigs when increased SID Thr:Lys ratio was in- suggested an increase in the requirement, the response was cluded in high-fiber diets compared with pigs fed a low-fiber small and almost impossible to measure. Furthermore, Zhu diet. The diets used were formulated to contain high and et al. (2005) fed growing pigs increasing levels of dietary low fibers by including soybean hulls (15% or 0% soybean pectin from 0% to 12% and an additional treatment that hulls, respectively), which is both an insoluble and soluble provided 8% cellulose. A linear decrease in ileal digestible fiber source. Mathai et al. (2016) included 45%, 54%, 63%, Thr utilization for protein deposition was observed as pectin 72%, 81%, and 90% SID Thr:Lys ratios for pigs from 25 increased in the diet; however, the cellulose level of the diet to 50 kg BW. The quadratic curve estimation for maximum did not influence the utilization of Thr, suggesting that fiber Fiber and threonine in finishing pig diets 5 Table 3. Interactive effects of DDGS and Thr on grow-finish pig performance Item No DDGS DDGS SEM P = || $ || $ Normal Thr High Thr Normal Thr High Thr Thr × DDGS Thr DDGS Initial BW, kg Day 0 35.1 35.1 35.1 34.9 0.47 0.384 0.503 0.259 Day 56 84.1 84.8 80.9 80.5 0.67 0.222 0.755 <0.001 Day 112 136.6 136.9 133.6 133.3 0.80 0.655 0.972 <0.001 Day 0 to 56 ADG, kg 0.90 0.90 0.84 0.84 0.011 0.635 0.986 <0.001 ADFI, kg 2.10 2.14 2.18 2.15 0.029 0.168 0.651 0.081 G:F 0.429 0.421 0.387 0.389 0.0039 0.133 0.379 <0.001 Day 56 to 112 ADG, kg 0.94 0.94 0.96 0.97 0.016 0.597 0.926 0.019 ADFI, kg 3.12 3.15 3.29 3.29 0.044 0.488 0.572 0.004 G:F 0.304 0.299 0.292 0.293 0.0037 0.294 0.547 0.004 Day 0 to 112 ADG, kg 0.92 0.92 0.89 0.89 0.006 0.989 0.973 <0.001 ADFI, kg 2.59 2.64 2.72 2.71 0.027 0.252 0.556 <0.001 G:F 0.356 0.350 0.331 0.332 0.0030 0.164 0.408 <0.001 A total of 2,160 pigs were used in two groups with 27 pigs per pen and 10 replicates per treatment. Phase 1 was fed from day 0 to 28, phase 2 from day 28 to 56, phase 3 from day 56 to 84, and phase 4 from day 84 to 112. DDGS included at 40% in phases 1 and 2, 30% in phase 3, and 15% in phase 4. || SID Thr:Lys was 61%, 62%, 63%, and 65% in phases 1, 2, 3, and 4, respectively. SID Thr:Lys was 67%, 68%, 69%, and 72% in phases 1, 2, 3, and 4, respectively. Table 4. Main effects of DDGS and Thr on grow-finish pig performance DDGS SEM P = Thr SEM P = || $ No DDGS High DDGS Normal Thr High Thr Initial BW, lb Day 0 35.1 34.9 0.46 0.259 35.1 35.0 0.46 0.503 Day 56 84.4 80.7 0.59 <0.001 82.5 82.6 0.59 0.755 Day 112 136.7 133.4 0.63 <0.001 135.1 135.1 0.63 0.972 Day 0 to 56 ADG, l kg 0.90 0.84 0.010 <0.001 0.87 0.87 0.010 0.986 ADFI, kg 2.12 2.16 0.023 0.081 2.14 2.15 0.023 0.651 G:F 0.425 0.388 0.0032 <0.001 0.408 0.405 0.0032 0.379 Day 56 to 112 ADG, kg 0.95 0.96 0.014 0.019 0.96 0.95 0.014 0.926 ADFI, kg 3.14 3.29 0.038 <0.001 3.21 3.22 0.038 0.572 G:F 0.302 0.293 0.0029 0.004 0.298 0.296 0.0029 0.547 Day 0 to 112 ADG, kg 0.92 0.89 0.004 <0.001 0.91 0.91 0.004 0.973 ADFI, kg 2.61 2.71 0.019 <0.001 2.66 2.67 0.019 0.556 G:F 0.353 0.332 0.0024 <0.001 0.343 0.341 0.0024 0.408 A total of 2,160 pigs were used in two groups with 27 pigs per pen and 10 replicates per treatment. Phase 1 was fed from day 0 to 28, phase 2 from day 28 to 56, phase 3 from day 56 to 84, and phase 4 from day 84 to 112. DDGS included at 40% in phases 1 and 2, 30% in phase 3, and 15% in phase 4. || SID Thr:Lys was 61%, 6%2, 63%, and 65% in phases 1, 2, 3, and 4, respectively. SID Thr:Lys was 67%, 68%, 69%, and 72% in phases 1, 2, 3, and 4, respectively. type may have an impact on the Thr requirement. Soluble decreased with no ameliorating effect of increasing digest - fiber includes pectins, gums, and β-glucans, whereas in- ible Thr. Therefore, this presents the possibility that the soluble fiber includes cellulose and hemicellulose (Jha and greater insoluble fiber content of DDGS may not result in Berrocoso, 2015). In the current study, only DDGS (a source an increased need for digestible Thr:Lys ratio above the pigs’ of insoluble fiber) was used in the diet, and pig performance current estimated requirement. 6 Tolosa et al. Kerr, B. J., W. A. Dozier III, and G. C. Shurson. 2013. Effects of reduced- The current study corroborated that the high inclusion (i.e., oil corn distillers dried grains with solubles composition on digesti - 40%) of corn co-products, such as DDGS, which is used in ble and metabolizable energy value and prediction in growing pigs. grow-finishing diets at the expense of corn and soybean meal, J. Anim. Sci. 91:3231–3243. doi:10.2527/jas.2013-6252 negatively impacts growth performance. Hardman (2013) Law, G. K., R. F. Bertolo, A. Adjiri-Awere, P. B. Pencharz, and R. O. observed that increasing DDGS inclusion from 0% to 40% Ball.2007. Adequate oral threonine is critical for mucin pro - in the diet for grow-finish pigs from 23 to 128  kg linearly duction and gut function in neonatal piglets.Am. J. Physiol. reduced ADG and resulted in a 1.4-kg reduction in weight Gastrointest. Liver Physiol. 292:G1293–G1301. doi:10.1152/ after 120 d compared with pigs fed the diet without DDGS. ajpgi.00221.2006 A cooperative study by Cromwell et al. (2011) included 560 Le Flocʹh, N., and B. Sève. 2005. Catabolism through the threonine pigs from nine university research stations and fed pigs from dehydrogenase pathway does not account for the high first-pass extraction rate of dietary threonine by the portal drained viscera in 32 to 120 kg diets with increasing levels of DDGS from 0% pigs. Br. J. Nutr. 93:447–456. doi:10.1079/bjn20051375 to 45% resulting in a linear decrease in ADG and in a 3-kg Mathai, J. K., J. K. Htoo, J. E. Thomson, K. J. Touchette, and H. H. reduction in final BW. These results are in agreement with the Stein. 2016. Effects of dietary fiber on the ideal standardized il - current study where feeding a diet with DDGS to pigs from 35 eal digestible threonine:lysine ratio for twenty-five to fifty kilogram to 136 kg decreased gain and feed efficiency, and reduced final growing gilts. J. Anim. Sci. 94:4217–4230. doi:10.2527/jas.2016- BW by 3.2 kg compared with pigs fed diets without DDGS. 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Journal

Translational Animal ScienceOxford University Press

Published: May 6, 2022

Keywords: DDGS; grow-finish pigs; growth; insoluble fiber; threonine

References