Abstract
Two experiments were conducted to evaluate the inclusion rate roughage in wheat-based diets containing modified distillers grains with solubles (MDGS) on feedlot performance (Feedlot Experiment), as well as digestibility, ruminal pH, and ruminal fermentation characteristics (Digestibility Experiment). The feedlot experiment utilized 72 Angus steers (392 ± 46.3 kg initial body weight) which were randomly assigned to 1 of 12 pens, 3 pens per treatment, to evaluate feedlot performance and carcass characteristics. Dietary treatments were 1) control; 10% roughage, 2) 12% roughage, 3) 14% roughage, and 4) 16% roughage. The digestibility experiment used four ruminally and duodenally cannulated steers (393 ± 33.0 kg) in a 4 × 4 Latin Square with either 10%, 12%, 14%, or 16% roughage as in the feedlot experiment. However, dietary roughage source was different between these two experiments and included a combination of grass hay and wheat straw (Feedlot Experiment), and corn silage (Digestibility Experiment). All data were analyzed with the Mixed Procedures of SAS. Feed intake was recorded, with duodenal and fecal output calculated using chromic oxide. Ruminal pH and fermentation were assessed. Growth performance and most carcass characteristics were not affected by increasing roughage (P ≥ 0.11). Marbling tended to decrease linearly (P = 0.10) with increasing roughage inclusion. Increasing dietary roughage content had no effect on organic matter intake (P = 0.60) in the digestibility experiment. Intake, duodenal flow, and digestibility of neutral detergent fiber and acid detergent fiber were not affected by treatment (P ≥ 0.16). Ruminal pH increased linearly (P < 0.01) as rate of roughage inclusion increased. Ruminal concentrations of acetate and butyrate increased, and propionate decreased in a linear fashion (P < 0.01) thereby increasing (P < 0.01) acetate and butyrate to propionate ratio with increasing dietary roughage. Our data indicate that increasing roughage inclusion in wheat-based diets including 30% MDGS increased ruminal pH and shifted ruminal fermentation patterns. Additionally, increasing roughage inclusion did not affect feedlot performance in steers fed wheat at 36% to 42% of dietary dry matter in combination with 30% MDGS.
Keywords: beef cattle, modified distillers grains with solubles, roughage inclusion, ruminal pH, wheat
INTRODUCTION
Wheat can be used as an alternative grain in feedlot diets; however, its rapid rate of fermentation in the rumen increases the risk of acidosis (Kreikemeier et al., 1990; Bock et al., 1991). Cattle-fed high-grain diets are at risk of digestive disorders, which can be offset by increased dietary roughage (Wise et al., 1968; Owens et al., 1998; Gentry et al., 2016), or through other management strategies including strict bunk management. Increased roughage inclusion increases ruminal pH, minimizing the risk of digestive upset (Weiss et al., 2017). Survey data indicated that 8% to 12% roughage inclusion is typical for feedlot diets (Samuelson et al., 2016). Rate of roughage inclusion in the diet can negatively affect dry matter intake (DMI), average daily gain (ADG), and gain to feed (G:F) if provided in excess (Galyean and Defoor, 2003). Likewise feeding too little roughage may cause a reduced rate of gain as a result of digestive disorders (Galyean and Hubbert, 2014; Gentry et al., 2016).
Research on feeding wheat-based feedlot diets in combination with ethanol coproducts is limited. With the absence of starch in distillers grains with solubles, the occurrence of acidosis should be reduced and potentially decreasing the amount of roughage needed in a diet (Krehbiel et al., 1995; Farran et al., 2006; Klopfenstein et al., 2008). Including wet distillers grains with solubles (WDGS) in combination with highly fermentable grains such as dry-rolled corn increased ruminal pH (Hales et al., 2014). Our hypothesis is that increasing roughage inclusion in wheat-based diets including MDGS would decrease feedlot performance and diet digestibility while increasing ruminal pH. The objective of this experiment was to evaluate the impacts of including additional roughage on feedlot performance, nutrient digestibility, ruminal fermentation, and ruminal pH of steers fed wheat-based feedlot rations containing 30% modified distillers grains with solubles (MDGS).
MATERIALS AND METHODS
These experiments were approved by the North Dakota State University Institutional Animal Care and Use Committee prior to initiation of experiment procedures.
Feedlot Experiment
To accomplish the objective of this experiment, 72 yearling Angus steers (392 ± 46.3 kg initial body weight; BW) were assigned to 1 of 12 pens (n = 3 pens per treatment). Steers were randomly assigned to pen (six steers per pen) with pen randomly assigned to treatment. Pens were stocked at a similar density, approximately 58.3 m2 of pen space per animal. Dietary treatments were based on increasing concentration of dietary roughage and consisted of 1) control; 10% roughage, 2) 12% roughage, 3) 14% roughage, and 4) 16% roughage. Base roughage for the 10% diet contained 5% grass hay and 5% wheat straw, with additional 2%, 4%, and 6% wheat straw added with wheat grain decreased by equal concentrations to create the treatment diets. Final finishing diet composition and nutrient content are presented in Table 1.
Table 1.
Ingredient and nutrient composition of diets fed to steers in the feedlot experiment
| Item | Treatment1 | |||
|---|---|---|---|---|
| 10 | 12 | 14 | 16 | |
| Ingredients, % DM | ||||
| MDGS2 | 30.0 | 30.0 | 30.0 | 30.0 |
| Dry-rolled wheat | 42.1 | 40.1 | 38.1 | 36.1 |
| Grass hay | 5.0 | 5.0 | 5.0 | 5.0 |
| Dry-rolled corn | 15.0 | 15.0 | 15.0 | 15.0 |
| Wheat straw | 5.0 | 7.0 | 9.0 | 11.0 |
| Limestone | 1.5 | 1.5 | 1.5 | 1.5 |
| Supplement3 | 1.4 | 1.4 | 1.4 | 1.4 |
| Nutrient composition (DM basis) | ||||
| Dry matter, % | 71.9 | 71.6 | 72.3 | 69.6 |
| Crude protein, % | 19.5 | 18.9 | 18.6 | 18.9 |
| NEg4, Mcal/kg | 1.38 | 1.36 | 1.34 | 1.32 |
| NDF, % | 30.2 | 30.0 | 31.2 | 32.2 |
| ADF, % | 11.1 | 11.4 | 12.5 | 13.2 |
Treatment based on dietary roughage inclusion: 10 = 10% roughage; 12 = 12% roughage, 14 = 14% roughage, and 16 = 16% roughage.
Modified distillers grains with solubles.
Supplement contained 81.1% grain screenings; 7.5% calcium carbonate; 3.8% molasses; 6.5% vitamin and trace mineral premixes; and 1.2% monensin premix. The supplement was fed to provided 330 mg of monensin steer−1·d−1.
Net Energy values estimated based on NASEM (2016).
Upon arrival, cattle were weighed on two consecutive days for determination of initial BW. All calves received a growth-promoting implant (Synovex Choice, Zoetis Inc., Parsippany, NJ) at the initiation of the experiment. Diets were developed to adapt cattle in five equal steps from a 68% concentrate/32% roughage to a 90% concentrate/10% roughage diet over a period of 28 days. Steers were fed for a total of 119 days. Feed was provided once daily at 0700 h. Feed was provided to target clean bunks the following morning. At the conclusion of the feeding period, cattle were weighed on two consecutive days to determine final BW and shipped to a commercial abattoir for slaughter and subsequent carcass data collection. Hot carcass weights were collected within 30 min of exsanguination. Ribeye area, 12th-rib fat, and marbling score were measured by automated camera imaging and provided by the abattoir along with quality and yield grade data.
Digestibility Experiment
Animal diets and treatments.
Four steers (393 ± 33.0 kg BW) previously fit with ruminal and duodenal cannulas were used in a 4 × 4 Latin square design to evaluate the impacts roughage inclusion rate in a wheat-based diet containing 30% MDGS on intake, digestibility, ruminal fermentation, and pH. Steers had been previously adapted to a 90% concentrate/10% roughage diet containing wheat for a period of 3 weeks prior to the start of the experiment. Treatments were based on increasing amount of roughage in the diet and consisted of 1) control; 10% roughage, 2) 12% roughage, 3) 14% roughage, and 4) 16% roughage. As roughage increased with the addition of 2% to 6% wheat straw, wheat grain decreased by equal concentrations. Diet composition differed from the feedlot experiment as corn silage was the main source of roughage for the digestibility experiment instead of a combination of grass hay and wheat straw as in the feedlot experiment (Table 2). Steers were housed in individual stations (2.13 m × 1.73 m). Steers were fed a total mixed ration, two times a day at 0700 h and 1900 h, and had continuous access to water. Feed was provided (kg/d) = 3.830 + [0.0143 × (BW × 0.96)] as suggested (NASEM, 2016). Feed offered was adjusted at the start of each period. Orts, when present, were collected at 0700 h each day prior to feeding. As was the case in the feedlot experiment this feeding method resembled a clean-bunk management system.
Table 2.
Ingredient and nutrient composition of diets fed to steers in the digestibility experiment
| Item | Treatment1 | |||
|---|---|---|---|---|
| 10 | 12 | 14 | 16 | |
| Ingredients, % DM | ||||
| MDGS2 | 30.0 | 30.0 | 30.0 | 30.0 |
| Dry-rolled wheat | 36.7 | 34.7 | 32.7 | 30.7 |
| Corn silage | 20.0 | 20.0 | 20.0 | 20.0 |
| Dry-rolled corn | 10.0 | 10.0 | 10.0 | 10.0 |
| Wheat straw | 0.0 | 2.0 | 4.0 | 6.0 |
| Limestone | 0.8 | 0.8 | 0.8 | 0.8 |
| Supplement3 | 2.5 | 2.5 | 2.5 | 2.5 |
| Nutrient composition (DM Basis) | ||||
| Dry matter, % | 64.5 | 64.7 | 64.3 | 64.4 |
| Crude protein, % | 16.0 | 15.7 | 16.3 | 16.2 |
| NEg4, Mcal/kg | 1.38 | 1.36 | 1.33 | 1.31 |
| NDF, % | 41.1 | 42.3 | 43.1 | 41.8 |
| ADF, % | 14.6 | 14.8 | 18.9 | 16.6 |
Treatment: 10 = 10% roughage included as corn silage assuming 50:50 of roughage to concentrate in corn silage, 12 = 10% roughage from corn silage and 2% straw, 14 = 10% roughage from corn silage and 4% straw, and 16 = 10% roughage from corn silage and 6% straw.
Modified distillers grains with solubles.
The supplement contained a minimum of 10% CP, 1.5% crude fat, 17.5% Ca, 0.1% P, 6.5% salt, 1.1% Mg, 0.1% K, 400 mg/kg Cu, 1,400 mg/kg Zn, 176,400 IU/kg vitamin A, 44,100 IU/kg of vitamin D, 727 IU/kg vitamin E, and contained 1,102 g/metric ton monensin (BP Balancer 10 RM1000, Purina Animal Nutrition, Arden Hills, MN). Inclusion of supplement was based on 0.25kg steer−1·d−1 assuming a 10 kg dry matter intake.
Net Energy values estimated based on NASEM (2016).
Sample collection.
Each collection period consisted of a 7-day adaptation period and 7-day collection period. Feed and ort samples were collected once daily on day 7 to 13 and day 8 to 14, respectively, and composited for each steer and period. Chromic oxide (8 g) was placed into gelatin capsules and ruminally dosed at time of both feed deliveries from day 4 to day 12 as an external marker. Duodenal fluid (100 mL) and fecal grab samples were collected on day 10 through day 12 in a manner to allow for collection of a sample for every hour in a 12-h period (0700 to 1900). Duodenal samples were composited within each steer and period and frozen at −20 °C prior to analysis. Fecal samples were immediately frozen and stored at −20 °C before being composited and mixed with a stand mixer (Model H-600, Hobart Manufacturing Co., Troy, OH).
Ruminal fluid was collected on day 13 at −2, 0, 2, 4, 6, 8, 10, and 12 h relative to morning feeding. Following the −2 h collection, 200 mL of cobalt ethylenediamine tetraacetic acid (Co-EDTA) was dosed via ruminal cannula for determination of the ruminal fluid dilution rate (FDR). Using a suction strainer, 100 mL of ruminal fluid was collected, and pH was recorded using a pH meter probe (symphony B10P, VWR International, LLC., Radnor, PA). Ruminal fluid was then acidified with 1 mL of 7.2N Sulfuric acid and stored at −20 °C until analyzed for concentrations of cobalt, ammonia, and volatile fatty acids (VFAs). Calculations for fluid parameters followed procedures outlined by Galyean (2010).
Laboratory analysis.
Feed, orts, and fecal samples were dried in a forced-air oven (55 °C) for a minimum of 48 h. Dried samples were subsequently ground to pass through a 2-mm screen in a Wiley Mill (Arthur H. Thomas, Philadelphia, PA). Duodenal samples were freeze dried (Virtis Genesis 25LL, The Virtis Company Inc., Gardiner, NY) and ground in a Wiley Mill to pass through a 1-mm screen. Diet, ort, duodenal, and fecal samples were analyzed for DM, ash, crude protein (CP), phosphorus, and calcium, (methods 934.01, 942.05, 2001.11, 965.17, and 968.08, respectively; AOAC, 2010). Concentrations of neutral detergent fiber (NDF; Van Soest et al., 1991; as modified by Ankom Technology, Fairport, NY) and acid detergent fiber (ADF; Goering and Van Soest, 1970, as modified by Ankom Technology) were determined using an Ankom 200 Fiber Analyzer (Ankom Technology, Macedon, NY). Chromium concentrations were analyzed in duodenal and fecal samples by the spectrophotometric method (Fenton and Fenton, 1979).
Ruminal fluid samples were thawed at 4 °C prior to centrifugation at 20,000 × g for 20 min at 4 °C before resultant supernatant was collected for analysis of ammonia (Broderick and Kang, 1980). Rumen fluid VFA concentrations (Goetsch and Galyean, 1983) were quantified with gas chromatography (Hewlett-Packard 5890A Series II GC, Wilmington, DE) using a capillary column. Cobalt concentrations were determined with atomic absorption spectroscopic (model 3030B, PerkinElmer Inc., Wellesley, MA) methods described by Uden et al. (1980) using an air-plus-acetylene flame.
Bacterial cells were isolated from formaldehyde-treated ruminal contents. Ruminal contents were blended (Model 37b119, Waring, New Hartford, CT) and strained through four layers of cheesecloth. Samples were centrifuged at 500 × g for 20 min to allow for separation of feed particles and protozoa. The supernatant was further centrifuged at 30,000 × g for 20 min to create a bacteria pellet. The bacteria pellet was frozen, freeze-dried, and analyzed for DM, ash, and CP (methods 934.01, 942.05, 2001.11, respectively; AOAC, 2010), and purines (Zinn and Owens, 1986).
Statistical analysis.
Data were analyzed with the mixed procedures of SAS (SAS Instit. Inc., Cary, NC). The feedlot experiment was designed as a completely random design with pen serving as the experimental unit. Individual animal data (BW, ADG, and carcass characteristics) were averaged within pen to create pen values. The model included treatment as fixed effect, with pen(treatment) included as the random effect. The digestibility experiment was analyzed as a 4 × 4 Latin square design. The model included period and treatment as fixed effects. The random effect was steer. Data over time were analyzed as repeated measures, and the model included period, treatment, and time. The treatment × time interaction was initially included in the model but was not significant for any variables and was therefore removed. Covariant structures were tested, and Simple was used based on fit statistics. Means were separated based on increasing roughage inclusion rate using linear, quadratic, and cubic contrast statements. P-values ≤ 0.05 were considered significant, and P-values > 0.05 and ≤ 0.10 were considered tendencies.
RESULTS AND DISCUSSION
Feedlot Experiment
Steer BW, DMI, ADG, and G:F were not affected by rate of roughage inclusion (P ≥ 0.42; Table 3). Bock et al. (1991) reported decreased final weight, ADG, and hot carcass weight in steers fed wheat at concentrations greater than 26.9% (DM basis). Differences in our results and those of previous research can be explained by the concentration of wheat in the diet (0% to 80.5%; Bock et al., 1991), compared to smaller range of 36% to 42% of wheat inclusion in the current experiment. In vitro starch digestion was more rapid for wheat than corn, potentially leading to acute acidosis and decreased intake in feedlot cattle (Kreikemeier et al., 1987). In the current experiment we did not provide a non-wheat control treatment; therefore, comparing the impacts of wheat versus corn on steer performance is not possible. However, DMI (13.1 ± 0.36 kg/d) and ADG (2.15 ± 0.07 kg/d) do not appear to indicate negative impacts of our diets on steer performance.
Table 3.
Impacts of rate of roughage inclusion on feedlot performance and carcass characteristics of feedlot cattle fed wheat-based diets1
| Item | Treatment2 | SEM | P-value3 | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 10 | 12 | 14 | 16 | Trt | L | Q | C | ||
| Feedlot performance | |||||||||
| Initial weight, kg | 391.0 | 391.2 | 386.9 | 393.4 | 2.66 | 0.42 | 0.85 | 0.25 | 0.24 |
| Final weight, kg | 650.2 | 645.7 | 635.1 | 646.8 | 10.17 | 0.74 | 0.65 | 0.44 | 0.55 |
| ADG, kg/d | 2.2 | 2.1 | 2.1 | 2.2 | 0.07 | 0.50 | 0.72 | 0.21 | 0.48 |
| DMI, kg/d | 13.2 | 13.1 | 13.0 | 13.2 | 0.36 | 0.97 | 0.94 | 0.70 | 0.83 |
| Gain:feed | 0.17 | 0.16 | 0.16 | 0.17 | 0.008 | 0.87 | 0.83 | 0.48 | 0.73 |
| Carcass characteristics | |||||||||
| HCW, kg | 381.2 | 380.2 | 369.4 | 383.2 | 4.84 | 0.26 | 0.84 | 0.17 | 0.15 |
| Ribeye area, cm2 | 83.3 | 81.0 | 80.2 | 81.7 | 1.08 | 0.29 | 0.27 | 0.12 | 0.91 |
| Marbling4 | 499 | 439 | 455 | 445 | 15.7 | 0.11 | 0.10 | 0.12 | 0.20 |
| Back fat, cm | 1.1 | 1.2 | 1.2 | 1.2 | 0.09 | 0.75 | 0.34 | 0.69 | 0.88 |
| Quality grade5 | 10.4 | 9.8 | 10.0 | 10.0 | 0.19 | 0.20 | 0.17 | 0.16 | 0.30 |
| Yield grade | 3.1 | 3.3 | 3.3 | 3.4 | 0.13 | 0.58 | 0.26 | 0.56 | 0.63 |
n = 3 per treatment.
Treatment: 10 = 5% grass hay and 5% straw; 12 = 5% grass hay and 7% straw; 14 = 5% grass hay and 9% straw; and 16 = 5% grass hay and 11% straw.
P-values: Overall effect of treatment (Trt), linear (L), quadratic (Q), and cubic (C) contrasts.
Marbling score based on 400 = Small00.
Quality grade based on Low Choice (Ch−) = 10, High Prime (Pr+) = 15.
It was expected that cattle would have compensated for the energy dilution of added forage with greater DMI (Galyean and Defoor, 2003); however, this was not the case in the present experiment. Feedlot steer intake increased with increasing roughage (0%, 5%, 10%, or 15% roughage) inclusion in steam-flaked wheat diets, while feed efficiency and gain were greater at 5% to 10% roughage levels (Kreikemeier et al., 1990). However, DMI was not affected by increasing barley silage inclusion (0%–12% DM) in cannulated beef heifers fed barley-based diets (Chibisa et al, 2020). Hales et al. (2014) found no difference in DMI when alfalfa hay increased from 2% to 14% in steers fed diets containing 57% to 69% dry-rolled corn and 25% wet distillers grains with solubles. Certainly, the variety of roughage and grain sources, grain processing methods, and use or not of ethanol coproducts presented in the literature all affect DMI in some manner. Further research is needed to clarify at what point energy dilution would result in greater intake of steers fed dry rolled wheat with MDGS inclusion.
Our data showed no effect on ADG when dietary roughage increased from 10% to 16% with a 30% MDGS inclusion rate. Previous research reported increased ADG when alfalfa hay increased from 2% to 6% but decreased ADG when alfalfa hay increased from 6% to 14% (Hales et al., 2013). It is also possible that particle size may have altered the results of the current study. Both grass hay and wheat straw were ground with a common screen; thus, these two roughage sources were treated similarly. However, use of other roughage sources with different NDF concentration, or particle length could alter DMI and subsequently ADG, and should be considered when interpreting results of this study.
Hot carcass weight, ribeye area, back fat, quality, and yield grade were unaffected by rate of roughage inclusion (P ≥ 0.20). However, there was a tendency for marbling to decrease linearly (P = 0.10) with increasing rate of roughage inclusion. Similar to Hales et al. (2013), in the current feedlot experiment, HCW and most other carcass characteristics were not affected by increased roughage inclusion in the diet. Differences in results from Hales et al. (2013, 2014) and the current feedlot experiment could be due to the differences in roughage and/or grain sources and inclusion rate. While the majority of variables evaluated in the current study were not impacted by roughage inclusion it is worth noting that this is in contrast to many published studies with feedlot steers fed high-concentrate diets, and more studies would need to be conducted to verify these results.
Digestibility Experiment
Increasing inclusion rate of dietary roughage had no effect on intake, duodenal flow, or ruminal digestibility of organic matter (OM) (P ≥ 0.60; Table 4). Orts ranged from 0.0% to 3.0% of total feed offered and did not vary by treatment (P = 0.73; data not presented). Increasing rate of roughage inclusion tended to quadratically affect fecal output (P = 0.07), and total tract digestibility of OM (P = 0.08) with steers fed the 12% and 14% roughage diets having lesser fecal output of OM, and greater total tract OM digestibility than those fed 10% or 16% roughage diets. We did not observe any differences in organic matter intake (OMI) in the digestibility experiment which was expected given our method of feeding. Similar to our data, Weiss et al. (2017) found that roughage inclusion at 5% to 10% did not affect DMI or OMI. While Weiss et al. (2017) used ground corn stalks, our experiment used a combination of corn silage and wheat straw, and as discussed previously roughage source can impact DMI.
Table 4.
Impacts of rate of roughage inclusion on organic matter intake, flow, and digestion in steers fed wheat-based feedlot diets1
| Item | Treatments2 | SEM | P-value3 | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 10 | 12 | 14 | 16 | Trt | L | Q | C | ||
| Intake, kg/d | 9.38 | 9.29 | 9.15 | 9.45 | 0.356 | 0.60 | 0.93 | 0.25 | 0.53 |
| Fecal output, kg/d | 2.49 | 2.20 | 2.27 | 2.62 | 0.154 | 0.26 | 0.53 | 0.07 | 0.92 |
| Duodenal flow kg/d | |||||||||
| Bacterial | 0.13 | 0.12 | 0.13 | 0.12 | 0.030 | 0.94 | 0.80 | 0.88 | 0.61 |
| Feed | 3.93 | 3.76 | 3.74 | 3.96 | 0.390 | 0.95 | 0.97 | 0.58 | 0.95 |
| Total | 4.06 | 3.87 | 3.86 | 4.11 | 0.357 | 0.84 | 0.92 | 0.41 | 0.94 |
| Digestibility, % of intake | |||||||||
| Ruminal | 56.41 | 58.53 | 57.85 | 56.49 | 3.079 | 0.90 | 0.97 | 0.50 | 0.84 |
| Total Tract | 73.26 | 76.28 | 75.07 | 72.41 | 1.358 | 0.27 | 0.56 | 0.08 | 0.67 |
n = 4 per treatment.
Treatment: 10 = 10% roughage included as corn silage assuming 50:50 of roughage to concentrate in corn silage, 12 = 10% roughage from corn silage and 2% straw, 14 = 10% roughage from corn silage and 4% straw, and 16 = 10% roughage from corn silage and 6% straw.
P-values: Overall effect of treatment (Trt), linear (L), quadratic (Q), and cubic (C) contrasts.
Intake, fecal output, duodenal flow, and digestibility of CP were unaffected by treatment (P ≥ 0.23; Table 5). These lack of differences in CP digestibility and duodenal flow were not surprising given the lack of differences in OM fermentation. Intake, duodenal flow, fecal flow, ruminal digestibility, and total tract digestibility of NDF and ADF were not affected by treatment (P ≥ 0.16; Table 6). Unlike our experiment, Hales et al. (2014) reported a linear increase in NDF intake when alfalfa hay was increased in the diet from 2% to 14% of DM. While Weiss et al. (2017) found fecal output of NDF and ADF tended to increase with increasing roughage from 5% to 10%, the current experiment found no effect of increasing roughage from 10 to 16% on NDF or ADF intake or fecal output. Similarly, Crawford et al. (2008) found no effect on fecal output of NDF with increasing the level of roughage across treatments of 3.8%, 7.6% and 11.4% corn silage. With increasing roughage inclusion, Benton et al. (2015) found a linear increase in NDF intake and percent digestibility of NDF while the current experiment found no differences NDF intake and percent digestibility of NDF with increasing roughage. Differences in results are likely caused by different roughage source and inclusion rate of 3% corn stalks, 4% alfalfa, 6% corn stalks, or 8% alfalfa, compared to our roughage inclusion of 20% corn silage and 0% to 6% wheat straw. Similar to the current experiment, Crawford et al. (2008) reported no difference in duodenal flow and ruminal digestion of nutrients when roughage inclusion increased in the diet. It is also possible that the differences in results may be explained by inclusion of distillers grains co-products as not all research discussed here included distillers grains with solubles, or perhaps more simply that the differences in NDF and ADF concentration between treatments were small enough to not allow for determination of effects within our experiment.
Table 5.
Impacts of rate of roughage inclusion on crude protein intake, flow, and digestion in steers fed wheat-based feedlot diets1
| Item | Treatments2 | SEM | P-value3 | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 10 | 12 | 14 | 16 | Trt | L | Q | C | ||
| Intake, kg/d | 1.79 | 1.73 | 1.72 | 1.72 | 0.069 | 0.66 | 0.33 | 0.49 | 0.89 |
| Fecal output, kg/d | 0.47 | 0.42 | 0.44 | 0.50 | 0.036 | 0.23 | 0.41 | 0.07 | 0.93 |
| Microbial efficiency | 15.26 | 14.20 | 13.26 | 13.32 | 1.544 | 0.51 | 0.22 | 0.61 | 0.85 |
| Duodenal flow, kg/d | |||||||||
| Bacterial | 0.51 | 0.49 | 0.45 | 0.46 | 0.051 | 0.55 | 0.27 | 0.71 | 0.60 |
| Feed | 1.03 | 0.98 | 1.00 | 1.03 | 0.083 | 0.91 | 0.99 | 0.52 | 0.88 |
| Total | 1.54 | 1.47 | 1.45 | 1.48 | 0.114 | 0.84 | 0.62 | 0.54 | 0.94 |
| Digestibility, % of intake | |||||||||
| Apparent ruminal | 12.97 | 15.00 | 15.98 | 14.92 | 6.414 | 0.97 | 0.79 | 0.77 | 0.97 |
| True ruminal | 41.57 | 43.48 | 41.89 | 40.08 | 4.632 | 0.95 | 0.75 | 0.66 | 0.85 |
| Total tract | 73.53 | 75.70 | 74.66 | 70.64 | 1.730 | 0.29 | 0.26 | 0.12 | 0.98 |
n = 4 per treatment.
Treatment: 10 = 10% roughage included as corn silage assuming 50:50 of roughage to concentrate in corn silage, 12 = 10% roughage from corn silage and 2% straw, 14 = 10% roughage from corn silage and 4% straw, and 16 = 10% roughage from corn silage and 6% straw.
P-values: Overall effect of treatment (Trt), linear (L), quadratic (Q), and cubic (C) contrasts.
Table 6.
Impacts of rate of roughage inclusion on neutral detergent fiber (NDF) and acid detergent fiber (ADF) intake, flow, and digestion in steers fed wheat-based feedlot diets1
| Item | Treatments2 | SEM | P-value3 | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 10 | 12 | 14 | 16 | Trt | L | Q | C | ||
| NDF | |||||||||
| Intake. kg/d | 4.09 | 4.26 | 4.18 | 4.28 | 0.516 | 0.65 | 0.36 | 0.79 | 0.45 |
| Duodenal flow, kg/d | 1.36 | 1.28 | 1.38 | 1.50 | 0.107 | 0.52 | 0.30 | 0.31 | 0.71 |
| Fecal output, kg/d | 1.45 | 1.38 | 1.34 | 1.58 | 0.087 | 0.33 | 0.39 | 0.13 | 0.57 |
| Digestibility, % of intake | |||||||||
| Ruminal | 66.42 | 70.10 | 67.59 | 63.11 | 2.414 | 0.28 | 0.26 | 0.11 | 0.66 |
| Total tract | 63.93 | 65.24 | 66.18 | 61.91 | 1.905 | 0.48 | 0.57 | 0.19 | 0.59 |
| ADF | |||||||||
| Intake, kg/d | 1.47 | 1.47 | 1.84 | 1.70 | 0.148 | 0.16 | 0.09 | 0.54 | 0.15 |
| Duodenal flow, kg/d | 0.56 | 0.61 | 0.61 | 0.68 | 0.073 | 0.70 | 0.28 | 0.87 | 0.74 |
| Fecal output, kg/d | 0.72 | 0.69 | 0.68 | 0.88 | 0.068 | 0.22 | 0.16 | 0.14 | 0.50 |
| Digestibility, % of intake | |||||||||
| Ruminal | 59.40 | 57.87 | 63.87 | 56.77 | 6.336 | 0.81 | 0.94 | 0.64 | 0.43 |
| Total tract | 49.56 | 50.72 | 61.07 | 47.69 | 4.385 | 0.23 | 0.82 | 0.15 | 0.14 |
n = 4 per treatment.
Treatment: 10 = 10% roughage included as corn silage assuming 50:50 of roughage to concentrate in corn silage, 12 = 10% roughage from corn silage and 2% straw, 14 = 10% roughage from corn silage and 4% straw, and 16 = 10% roughage from corn silage and 6% straw.
P-values: Overall effect of treatment (Trt), linear (L), quadratic (Q), and cubic (C) contrasts.
Ruminal pH increased linearly (P < 0.01; Table 7) from 6.0 to 6.2 ± 0.07 with increasing roughage In feedlot diets, increasing roughage inclusion, among other factors can assist in maintaining ruminal pH above 5.6 and decrease acidosis (Owens et al., 1998). As anticipated, our data indicated that ruminal pH increased with greater roughage inclusion. The impacts of roughage inclusion on intake, gain, and ruminal pH of feedlot cattle have been documented (Galyean and Defoor, 2003; Galyean and Hubbert, 2014; Swanson et al., 2017). Increased dietary roughage leads to an increase in salivary buffers entering the rumen and offsetting acidosis (Weiss et al., 2017), potentially increasing intake and ADG in cattle with low ruminal pH; however, intake was not different between treatments in the current study.
Table 7.
Effects of rate of roughage inclusion on ruminal fluid pH, total volatile fatty acid concentrations, acetate, propionate, and butyrate proportions, and ruminal fluid kinetics in steers fed wheat-based feedlot diets1
| Item | Treatment2 | SEM | P-values3 | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 10 | 12 | 14 | 16 | Trt | L | Q | C | ||
| pH | 6.0 | 6.1 | 6.2 | 6.2 | 0.07 | <0.01 | <0.01 | 0.79 | 0.27 |
| Ammonia, mM | 12.6 | 12.1 | 12.9 | 11.9 | 1.64 | 0.51 | 0.57 | 0.62 | 0.19 |
| Volatile fatty acids | |||||||||
| Total, mM | 139.1 | 128.9 | 119.6 | 120.6 | 5.41 | <0.01 | <0.01 | 0.09 | 0.51 |
| Acetate, % | 49.7 | 49.5 | 52.6 | 53.9 | 1.60 | <0.01 | <0.01 | 0.10 | 0.01 |
| Propionate, % | 27.8 | 29.2 | 23.1 | 22.0 | 3.12 | <0.01 | <0.01 | 0.16 | <0.01 |
| Butyrate, % | 11.0 | 10.9 | 12.9 | 13.0 | 1.26 | <0.01 | <0.01 | 0.78 | 0.03 |
| Ac + Bu:Pr4 | 2.5 | 2.4 | 3.1 | 3.1 | 0.36 | <0.01 | <0.01 | 0.47 | <0.01 |
| Fluid kinetics5 | |||||||||
| FDR, % h | 8.9 | 9.1 | 8.0 | 8.5 | 0.78 | 0.66 | 0.44 | 0.80 | 0.38 |
| Volume, L | 66.2 | 70.5 | 80.2 | 81.6 | 7.01 | 0.09 | 0.02 | 0.73 | 0.48 |
| FTO, h | 12.0 | 11.1 | 12.8 | 11.8 | 0.96 | 0.52 | 0.74 | 0.98 | 0.17 |
| FFR, L/h | 5.6 | 6.4 | 6.5 | 6.9 | 0.49 | 0.38 | 0.12 | 0.70 | 0.63 |
n = 4.
Treatment: 10 = 10% roughage included as corn silage assuming 50:50 of roughage to concentrate in corn silage, 12 = 10% roughage from corn silage and 2% straw, 14 = 10% roughage from corn silage and 4% straw, and 16 = 10% roughage from corn silage and 6% straw.
P-values: Overall effect of treatment (Trt), linear (L), quadratic (Q), and cubic (C) contrasts.
Acetate plus butyrate to propionate ratio.
FDR = Fluid dilution rate (% h), FTO = fluid turnover time (h), FFR = fluid flow rate (L/h).
Both Weiss et al. (2017) and Sindt et al. (2003) found increases in ruminal pH when increasing roughage from 5% to 10% and 0% to 6%, respectively. It was expected that ruminal pH would increase as dietary roughage increased from 10% to 16%. Increasing ruminal pH with an increase in roughage can potentially be explained by increased chewing time increasing saliva that carries buffers to the rumen (Owens et al., 1998; Weiss et al., 2017). Changes in ruminal pH due to roughage inclusion at rates below 10% when including wheat would likely be much different than those observed in the current experiment. The potential for decreased incidence of digestive upset, like acidosis, is likely the justification for the 8% to12% roughage inclusion rates reported by Samuelson et al. (2016). Including distillers grains can reduce the amount of roughage needed in the diet (Krehbiel et al., 1995; Farran et al., 2006; Klopfenstein et al., 2008). Adding distillers grains with solubles reduces the amount of starch in the diet while increasing fiber, protein, and fat which reduces the need for excess roughage (Klopfenstein et al., 2008). Both portions of the current experiment include 30% MDGS across all treatments, potentially offsetting a decrease in ruminal pH and occurrence of subacute acidosis.
Total VFA concentration (mM) decreased linearly with increasing roughage inclusion (P < 0.01). Ruminal acetate and butyrate proportion increased while propionate proportion decreased linearly with increased inclusion of roughage (P < 0.01). The ratio of acetate + butyrate to propionate in ruminal fluid increased linearly (P < 0.01) with increasing roughage inclusion in the diet. FDR, fluid turnover rate, and fluid flow rate were not affected by treatment (P ≥ 0.38). Fluid volume increased linearly (P = 0.02) with increasing roughage inclusion in the diet.
Similar to our digestibility experiment data, Chibisa et al. (2020) found an increase in ruminal acetate and butyrate along with the acetate to propionate ratio while increasing dietary roughage. Chibisa et al. (2020) also found a quadratic decrease in the propionate proportion with increasing roughage. Axe et al. (1987) found a decrease in acetate to propionate ratio and acetate proportion but an increase in propionate proportion and total VFA concentration with increasing wheat concentration in the diet from 0% to 80%. Data from Axe et al. (1987) potentially differ from our metabolism data due to differences in wheat concentration in the diet. Wheat inclusion in our diets was much smaller 36% to 42% of dietary DM.
CONCLUSIONS
In conclusion, our data appear to indicate that increasing roughage inclusion from 10 to 16% of dietary DM in wheat-based diets including 30% MDGS did not impact feedlot performance, had minimal impacts on organic matter digestibility, and increased ruminal pH. The lack of pH indicative of subacute acidosis in our digestibility experiment, and our feedlot performance data indicate that feeding combinations of MDGS and wheat may be possible without the need to increase roughage inclusion rates. As our current experiment used a small number of feedlot cattle, additional research is warranted. Evaluation of feeding wheat in combination with MDGS to lightweight feedlot cattle may also be justifiable as lightweight cattle are likely less adapted to consuming grain at feedlot arrival and will consume finishing diets longer than the heavier weight cattle in our current experiment.
Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. USDA is an equal opportunity provider and employer. Portions of this manuscript were presented at Western Section American Society of Animal Science Meetings and awarded the Applied Animal Science Award in 2021.
Contributor Information
Wayde J Pickinpaugh, Carrington Research Extension Center, North Dakota State University, Carrington, ND 58421, USA.
Bryan W Neville, Carrington Research Extension Center, North Dakota State University, Carrington, ND 58421, USA; U.S. Meat Animal Research Center, USDA, Agricultural Research Service, Clay Center, NE 68933, USA.
Rebecca L Moore, Carrington Research Extension Center, North Dakota State University, Carrington, ND 58421, USA.
Joel S Caton, Department of Animal Sciences, North Dakota State University, Fargo, ND 58108, USA.
Conflict of interest statement
None declared.
LITERATURE CITED
- AOAC. 2010. Official methods of analysis. 18th ed. Arlington (VA): Association of Official Analytical Chemists. [Google Scholar]
- Axe, D. E., Bolsen K. K., Harmon D. L., Lee R. W., Milliken G. A., and Avery T. B.. . 1987. Effect of wheat and high-moisture sorghum grain fed singly and in combination on ruminal fermentation, solid and liquid flow, site and extent of digestion and feeding performance of cattle. J. Anim. Sci. 64:897–906. doi: 10.2527/jas1987.643897x. [DOI] [PubMed] [Google Scholar]
- Benton, J. R., Watson A. K., Erickson G. E., Klopfenstein T. J., Vander Pol K. J., Meyer N. F., and Greenquist M. A.. . 2015. Effects of roughage source and inclusion in beef finishing diets contain corn wet distillers’ grains plus solubles. J. Anim. Sci. 93:4358–4367. doi: 10.2527/jas.2015-9211. [DOI] [PubMed] [Google Scholar]
- Bock, B. J., R. T.Brandt, Jr, Harmon D. L., Anderson S. J., Elliott J. K., and Avery T. B.. . 1991. Mixtures of wheat and high-moisture corn in finishing diets: feedlot performance and in situ rate of starch digestion in steers. J. Anim. Sci. 69:2703–2710. doi: 10.2527/1991.6972703x. [DOI] [PubMed] [Google Scholar]
- Broderick, G. A., .J. H.Kang. . 1980. Automated simultaneous determination of ammonia and total amino acids in ruminal fluid and in vitro media. J. Dairy Sci. 63:64–75. doi: 10.3168/jds.S0022-0302(80)82888-8. [DOI] [PubMed] [Google Scholar]
- Chibisa, G. E., Beauchemin K. A., Koenig K. M., and Penner G. B.. . 2020. Optimum roughage proportion in barley-based feedlot cattle diets: total tract nutrient digestibility, rumination, ruminal acidosis, short-chain fatty absorption, and gastrointestinal tract barrier function. J. Anim. Sci. 98:160. doi: 10.1093/jas/skaa160. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Crawford, G. I., Keeler C. D., Wagner J. J., Krehbiel C. R., Erickson G. E., Crombie M. B., and Nunnery G. A.. . 2008. Effects of calcium magnesium carbonate and roughage level on feedlot performance, ruminal metabolism, and site and extent of digestion in steers fed high-grain diets. J. Anim. Sci. 86:2998–3013. doi: 10.2527/jas.2007-0070. [DOI] [PubMed] [Google Scholar]
- Farran, T. B., Erickson G. E., Klopfenstein T. J., Macken C. N., and Lindquist R. U.. . 2006. Wet corn gluten feed and alfalfa hay levels in dry-rolled corn finishing diets: Effects on finishing performance and feedlot nitrogen mass balance. J. Anim. Sci. 84:1205–1214. doi: 10.2527/2006.8451205x. [DOI] [PubMed] [Google Scholar]
- Fenton, T. W., and Fenton M.. . 1979. An improved procedure for the determination of chromic oxide in feed and feces. Can. J. Anim. Sci. 59:631–634. doi: 10.4141/cjas79-081. [DOI] [Google Scholar]
- Galyean, M. L. 2010. Laboratory procedures in animal nutrition research. Lubbock (TX): Department of Animal and Food Sciences, Texas Tech University. [Google Scholar]
- Galyean, M. L., and Defoor P. J.. . 2003. Effects of roughage source and level on intake by feedlot cattle. J. Anim. Sci. 81:E8–E16. doi: 10.2527/2003.8114_suppl_2E8x. [DOI] [PubMed] [Google Scholar]
- Galyean, M. L., and Hubbert M. E.. . 2014. Review: Traditional and alternative sources of fiber—Roughage values, effectiveness, and levels in starting and finishing diets. Prof. Anim. Sci. 30:571–584. doi: 10.15232/pas.2014-01329. [DOI] [Google Scholar]
- Gentry, W. W., Weiss C. P., Meredith C. M., McCollum F. T., Cole N. A., and Jennings J. S.. . 2016. Effects of roughage inclusion and particle size on performance and rumination behavior of finishing beef steers. J. Anim. Sci. 94:4759–4770. doi: 10.2527/jas.2016-0734. [DOI] [PubMed] [Google Scholar]
- Goering, H. K., and Van Soest P. J.. . 1970. Forage fiber analysis (Apparatus, Reagents, Procedures, and Some Applications). Agriculture Handbook No. 379. Washington, DC: ARS-USDA. [Google Scholar]
- Goetsch, A. L. and Gaylean M. L.. . 1983. Influence of feeding frequency on passage of fluid and particulate markers in steers fed a concentrate diet. Can. J. Anim. Sci. 63:727–730. doi: 10.4141/cjas83-084. [DOI] [Google Scholar]
- Hales, K. E., Freetly H. C., Shackelford S. D., and King D. A.. . 2013. Effects of roughage concentration in dry-rolled corn-based diets containing wet distillers grains with solubles on performance and carcass characteristics of finishing beef steers. J. Anim. Sci. 91:3315–3321. doi: 10.2527/jas.2012-5942. [DOI] [PubMed] [Google Scholar]
- Hales, K. E., Brown-Brandl T. M., and Freetly H. C.. . 2014. Effects of decreased dietary roughage concentration on energy metabolism and nutrient balance in finishing beef cattle. J. Anim. Sci. 92:264–271. doi: 10.2527/jas.2013-6994. [DOI] [PubMed] [Google Scholar]
- Klopfenstein, T. J., Erickson G. E., and Bremer V. R.. . 2008. Board invited review: Use of distillers by-products in the beef cattle feeding industry. J. Anim. Sci. 86:1223–1231. doi: 10.2527/jas.2007-0550. [DOI] [PubMed] [Google Scholar]
- Krehbiel, C. R., Stock R. A., Herold D. W., Shain D. H., Ham G. A., and Carulla J. E.. . 1995. Feeding wet corn gluten feed to reduce subacute acidosis in cattle. J. Anim. Sci. 73:2931–2939. doi: 10.2527/1995.73102931x. [DOI] [PubMed] [Google Scholar]
- Kreikemeier, K. K., Harmon D. L., R. T.Brandt, Jr, Nagaraja T. G., and Cochran R. C.. . 1990. Steam-rolled wheat diets for finishing cattle: effects of dietary roughage and feed intake on finishing steer performance and ruminal metabolism. J. Anim. Sci. 68:2130–2141. doi: 10.2527/1990.6872130x. [DOI] [PubMed] [Google Scholar]
- Kreikemeier, K. K., Stock R. A., Brink D. R., and Britton R. A.. . 1987. Feeding combinations of dry corn and wheat to finishing lambs and cattle. J. Anim. Sci. 65:1647–1654. doi: 10.2527/jas1987.6561647x. [DOI] [PubMed] [Google Scholar]
- National Academies of Science, Engineering, and Medicine (NASEM). 2016. Nutrient requirements of beef cattle. 8th rev. ed. Washington, DC: The National Academies Press. [Google Scholar]
- Owens, F. N., Secrist D. S., Hill W. J., and Gill D. R.. . 1998. Acidosis in cattle: A review. J. Anim. Sci. 76:275–286. doi: 10.2527/1998.761275x. [DOI] [PubMed] [Google Scholar]
- Samuelson, K. L., Hubbert M. E., Galyean M. L., and Löest C. A.. . 2016. Nutritional recommendations of feedlot consulting nutritionists: The 2015 New Mexico State and Texas Tech University Survey. J. Anim. Sci. 94:2648–2663. doi: 10.2527/jas2016-0282. [DOI] [PubMed] [Google Scholar]
- Sindt, J. J., Drouillard J. S., Titgemeyer E. C., Montgomery S. P., Coetzer C. M., Farran T. B., Pike J. N., Higgins J. J., and Ethington R. T.. . 2003. Wet corn gluten feed and alfalfa hay combinations in steam-flaked corn finishing cattle diets. J. Anim. Sci. 81:3121–3129. doi: 10.2527/2003.81123121x. [DOI] [PubMed] [Google Scholar]
- Swanson, K. C., Carlson Z. E., Rush M. C., Gilbery T. C., Underdahl S. R., Keomanivong F. E., Bauer M. L., and Islas A.. . 2017. Influence of forage source and forage inclusion level on growth and performance, feeding behavior, and carcass characteristics in finishing steers. J. Anim. Sci. 95:1325–1334. doi: 10.2527/jas2016.1157. [DOI] [PubMed] [Google Scholar]
- Uden, P., Colucci P. E., and Van Soest P. J.. . 1980. Investigation of chromium, cerium and cobalt as markers in digesta. Rate of passage studies. J. Sci. Food Agric. 31:625–632. doi: 10.1002/jsfa.2740310702. [DOI] [PubMed] [Google Scholar]
- Van Soest, P. J., Robertson J. B., and Lewis B. A.. . 1991. Methods for dietary fiber, neutral detergent fiber, and non-starch polysacchardies in relation to animal nutrition. J. Dairy Sci. 74:3583–3597. doi: 10.3168/jds.S0022-0302(91)78551-2. [DOI] [PubMed] [Google Scholar]
- Weiss, C. P., Gentry W. W., Meredith C. M., Meyer B. E., Cole N. A., Tedeschi L. O., F. T.McCollum, III, and Jennings J. S.. . 2017. Effects of roughage inclusion and particle size on digestion and ruminal fermentation characteristics of beef steers. J. Anim. Sci. 95:1707–1714. doi: 10.2527/jas.2016.1330. [DOI] [PubMed] [Google Scholar]
- Wise, M. B., Harvey R. W., Haskins B. R., and Barrick E. R.. . 1968. Finishing beef cattle on all concentrate rations. J. Anim. Sci. 27:1449–1461. doi: 10.2527/jas1968.2751449x. [DOI] [Google Scholar]
- Zinn, R. A., and Owens F. N.. . 1986. A rapid procedure for purine measurements and its use for estimating net ruminal protein synthesis. Can. J. Anim. Sci. 66:157–166. doi: 10.4141/cjas86-017. [DOI] [Google Scholar]