Replacing DDGS with heat-treated soybean meal
What impact does TSBM in forage-based diets have on cattle performance?
By Grady Gullickson
For nearly two decades, the production of ethanol leading to the availability of the coproduct, distillers grains with solubles, has provided an economical protein source, relative to soybean meal, for beef cattle diets. However, the expansion and onboarding of several new soybean crush facilities to extract soy oil for biodiesel may decrease the price of solvent-extracted soybean meal (SBM); potentially mimicking the increase in ethanol production and decrease in dried distillers grains with solubles (DDGS) price in the early 2000s. In both cases, governmental and environmental regulations are driving the substantial increase in alternative fuel production. Therefore, we may witness increased supply and lower prices for SBM in the future.
Soybean meal is a great protein source (53% crude protein [CP] on a dry matter [DM] basis) that offers a balanced amino acid profile and is also very degradable in the rumen (70% rumen degradable protein [RDP]). Approaches to decrease the ruminal degradability of SBM and increase the flow of feed amino acids to bypass the rumen have been utilized for many years. The most common approaches utilizes non-enzymatic browning with glucose or xylose and heat to initiate the Maillard reaction for the protection of amino acids from ruminal degradation. The non-enzymatically browned SBM (TSBM) product decreases the RDP concentration to approximately 30%, resulting in increased flow of feed amino acids to the small intestine.
Heat-treated soybean meal is a nutritionally attractive feedstuff that contains greater lysine and rumen undegradable protein (RUP) concentrations than DDGS and could potentially improve growing cattle performance. Lysine is one of the most limiting amino acids in beef cattle diets, especially with corn-based diets. Increasing the supply of lysine and RUP to the growing animal has resulted in improved growth performance.
Therefore, the current study evaluated the effects of increasing the metabolizable protein (MP) and lysine concentrations by replacing DDGS with increased levels of TSBM on growth performance and nutrient digestibility.
Experiment 1: Cattle growth performance Seventy Angus-based steers (initial body weight [BW] = 656 ± 35 lb) were utilized in an 85-day experiment at the North Dakota State University Beef Cattle Research Complex in Fargo, North Dakota. Steers were housed in a monoslope barn with drylot access.
Heat-treated soybean meal (AminoPlus®; Ag Processing, Inc., Omaha, Nebraska) replaced DDGS at levels of 0 (TSBM0), 4 (TSBM4), 8 (TSBM8), and 12% of the diet DM (TSBM12; Table 1). Diets also contained 44% corn silage, 37% oat hay and 3% dry meal supplement (DM basis). The MP balance was modeled to be in excess of the steers’ requirements whereas lysine was modeled to be deficient for TSBM0, TSBM4 and TSBM8 treatments and in excess for TSBM12.
On day 0, steers were implanted with 80 mg trenbolone acetate and 16 mg of estradiol (Revalor-IS, Merck Animal Health, Summit, New Jersey). Before the initiation of the study, steers were limit-fed a common diet at 1.8% BW for five days to minimize gut fill variation followed by three days of weighing. The average of the consecutive three-day weights served as the initial BW. Steers were blocked by initial BW into light, medium, and heavy blocks and assigned randomly to treatments. After completion of the study, steers were limit-fed, and the three-day weighing process was repeated to measure ending BW.
Daily individual intakes were recorded by utilizing an automated feed intake monitoring system (Insentec Roughage Intake Control, Hokofarm B. V., Marknesse, The Netherlands). Body weights were recorded every 28 days to monitor interim performance. Blood was collected every 28 days via jugular venipuncture for the analysis of plasma urea nitrogen (PUN), glucose, and non-esterified fatty acids (NEFA).
After the experimental period, steers were transported to the NDSU Central Grasslands Research and Extension Center. All steers received a common diet of corn, DDGS and liquid supplement for 150 days. Corn silage and hay was utilized as forage sources. Steers were transported to a commercial abattoir and carcass characteristics were collected.
Experiment 2: Nutrient flow and digestibilityFive Jersey steers fitted with ruminal, duodenal, and ileal cannulas were utilized in a 4 × 5 Latin square design at the Animal Nutrition and Physiology Center in Fargo, North Dakota. The four-period study, totaling 56 days, consisted of nine days of adaptation and five days of collection per period.
Dietary treatments are the same as described in Experiment 1. Chromic oxide was incorporated into the diet daily at 0.25% DM as a digesta marker.
Daily individual intakes were determined by weighing orts. Fecal collection bags were fitted on each steer to collect feces twice daily during the collection period. Duodenal and ileal digesta samples were collected across three days to obtain 12 timepoints to represent every other hour in a 24-hour cycle.
Dry matter, organic matter, neutral detergent fiber, acid detergent fiber and starch were analyzed for this experiment; however, only nitrogen and lysine will be discussed further.
ResultsFor the growth performance study, replacing DDGS with TSBM did not affect (P ≥ 0.14) ending body weight (EBW), average daily gain (ADG), dry matter intake (DMI), and feed:gain (F:G; Table 2). Therefore, modeled increases in MP and lysine did not result in improved growth performance in growing cattle. No differences in glucose and NEFA concentrations were detected (P ≥ 0.34) at day 85 however PUN concentrations linearly increased (P = 0.01) as TSBM replaced DDGS.
There were no differences (P ≥ 0.21) in final body weight, hot-carcass weight, longissimus muscle area, 12th rib backfat thickness, marbling score and calculated yield grade on the residual effects during the growing phase.
For the digestion study, nitrogen (N) and lysine intake linearly increased (P = 0.01) with increased inclusion of TSBM. This aligns with the greater CP and lysine concentrations of TSBM compared to DDGS. There were no differences (P ≥ 0.11) in N and lysine flow at the duodenum, ileum and feces. Lysine flow at the ileum tended (P = 0.09) to decrease linearly as TSBM replaced DDGS.
True ruminal N digestibility linearly increased (P = 0.03) when TSBM replaced DDGS. This finding contradicts ruminally undegradable protein values reported for DDGS and TSBM (63 and 78%, respectively). The main goal of protected SBM is to escape the rumen and provide N and lysine postruminally. Post ruminal lysine digestibility (% of lysine entering the duodenum) linearly increased (P = 0.04) as TSBM replaced DDGS.
Nitrogen digestibility postruminally (% of N entering the duodenum) observed a quadratic effect (P = 0.02) which resulted in TSBM8 experiencing the greatest digestibility and TSBM12 the lowest. The Maillard reaction from the non-enzymatic browning process did not negatively affect the digestibility of lysine and N postruminally. Total tract digestibility linearly increased (P ≥ 0.01) for N and lysine with the substitution of DDGS with TSBM.
ImplicationsHeat-treated soybean meal can replace DDGS in forage-based growing diets without negatively affecting performance. Incremental increases in MP and lysine did not improve growth performance; however, it is difficult to distinguish between MP and lysine due to the lack of differences.
The inclusion of TSBM will be based on availability and feed costs and will likely be incorporated at low inclusion rates to increase lysine and N digestibility in growing diets.
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Gullickson is a graduate resesarch assistant at North Dakota State University.
