Comparison of wheat or corn dried distillers grains ...

Comparison of wheat or corn dried distillers grains with solubles on rumen fermentation and nutrient digestibility by feedlot heifers L. J. Walter, T. A. McAllister, W. Z. Yang, K. A. Beauchemin, M. He and J. J. McKinnon J ANIM SCI 2012, 90:1291-1300. doi: 10.2527/jas.2011-3844 originally published online October 21, 2011

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Comparison of wheat or corn dried distillers grains with solubles on rumen fermentation and nutrient digestibility by feedlot heifers1 L. J. Walter,* T. A. McAllister,† W. Z. Yang,† K. A. Beauchemin,† M. He,*† and J. J. McKinnon*2 *Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7H 5A8; and †Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada

ABSTRACT: A 5 × 5 Latin square design trial was conducted to evaluate rumen fermentation and apparent nutrient digestibility in 5 rumen-cannulated heifers (420 ± 6 kg) fed a barley-based finishing diet supplemented with 20 or 40% wheat or corn dried distillers grains with solubles (DDGS). The composition of the control diet was 88.7% rolled barley grain, 5.5% supplement, and 5.8% barley silage (DM basis). Increasing the quantity of corn DDGS in the ration resulted in a quadratic decrease in DMI (P = 0.04) and OM intake (P = 0.05). Rumen pH, pH duration, and area under rumen pH thresholds of 5.8 or 5.5 were not affected (P > 0.05) by treatment. Inclusion of wheat DDGS resulted in a quadratic increase (P = 0.05) in pH area below the cutoff value of 5.2, with the most pronounced effect at 20% inclusion. Wheat DDGS linearly increased (P = 0.01) rumen NH3-N concentrations. Increasing the inclusion rate of wheat and corn DDGS resulted in quadratic (P = 0.05) and linear (P = 0.04) decreases in rumen propionate, whereas butyrate increased quadratically (P < 0.01) and linearly (P < 0.01), respectively. Feeding wheat DDGS linearly decreased (P < 0.01) DM and OM digestibility values. Inclusion of corn DDGS

increased the digestibility values of ether extract (P = 0.05; quadratic response) and CP (P < 0.01; linear response). Neutral detergent fiber digestibility increased in a linear fashion (P = 0.01) as both wheat and corn DDGS inclusion increased, whereas ADF digestibility increased linearly (P = 0.03) for wheat and quadratically (P = 0.02) for corn DDGS. Increased inclusion of wheat DDGS resulted in a linear decrease in GE digestibility (P = 0.01), whereas increasing corn DDGS inclusion linearly increased (P < 0.01) the DE content of the diet. Feeding both wheat and corn DDGS linearly increased (P = 0.01) the excretion of N and P. In summary, replacement of barley grain with up to 40% wheat or corn DDGS did not mitigate rumen pH conditions associated with mild to moderate acidosis in heifers fed a barley-based finishing diet. Supplementing corn DDGS increased nutrient digestibility of all nutrients and, as a result, led to greater DE content. Supplementation of wheat DDGS reduced DM and OM digestibility values, with no effect on DE content. Increased N and P excretion by heifers fed DDGS at 20 or 40% of dietary DM presents a challenge for cattle feeders with respect to nutrient management.

Key words: corn, dried distillers grains with solubles, heifer, nutrient digestibility, rumen fermentation, wheat ©2012 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2012. 90:1291–1300 http://dx.doi.org/10.2527/jas.2011-3844

INTRODUCTION

1 This study was funded by the Canadian Cattlemen’s Association Beef Cattle Research Council (Calgary, Alberta, Canada), the Alberta Beef Producers (Calgary, Alberta, Canada), National Science and Engineering Research Council (Ottawa, Ontario, Canada), Advancing Canadian Agriculture and Agri-Food Saskatchewan (Agricultural Council of Saskatchewan, Saskatoon, Saskatchewan), and the Agriculture Bioproducts Innovation Program (Ottawa, Ontario, Canada). 2 Corresponding author: [email protected] Received January 4, 2011. Accepted October 18, 2011.

Starch is the primary source of glucose for ethanol production; as a result, the starch content of dried distillers grains with solubles (DDGS) is minimal (Spiehs et al., 2002). It has been speculated that the incidence of subacute acidosis is reduced when DDGS is substituted for cereal grain in feedlot diets (Firkins et al., 1985; Larson et al., 1993). The effects of DDGS feeding on rumen pH and fermentation parameters have been variable. Ham et al. (1994) did not find an effect of corn DDGS on ruminal pH or molar proportions of VFA when DDGS was fed at 40% of DM. In contrast, Leupp et al. (2009) reported that total VFA concen-

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trations and the proportion of acetate were decreased, whereas propionate was increased as up to 60% corn DDGS was substituted for corn grain. With respect to wheat DDGS, Beliveau and McKinnon (2009) reported that the concentration of propionate decreased as DDGS inclusion increased in barley-based rations. These authors also reported that wheat DDGS had a negative effect on rumen pH. The OM digestibility of corn DDGS has been shown to be comparable with that of dry-rolled corn when fed at quantities up to 60% of the ration DM (Leupp et al., 2009). Leupp et al. (2009) also reported that ruminal, but not total tract, digestion of ADF and NDF in cattle fed corn DDGS declined as the dietary inclusion amount increased. Spiehs and Varel (2009) reported that excretion of both N and P increased as corn wet distillers grains with solubles replaced corn (up to 60%) in high-concentrate rations. With regard to wheat DDGS, Gibb et al. (2008) reported that DM digestibility by cattle was 9.8% less for a 60% DDGS diet than for a barley-based finishing diet. To date, no research has been conducted to compare rumen fermentation parameters and the digestibility of wheat- vs. corn DDGS-based rations with typical barley-based feedlot diets. We hypothesized that the reported differences in performance and nutrient utilization of cattle fed wheat or corn DDGS were due to differences in nutrient composition of the 2 DDGS sources. The objectives of this study were to compare cattle fed wheat vs. corn DDGS at 2 inclusion amounts on rumen fermentation, nutrient digestibility, and N and P excretion.

MATERIALS AND METHODS All cattle were cared for in accordance with the guidelines of the Canadian Council on Animal Care (1993), under a University of Saskatchewan Animal Care Protocol.

Animals, Housing, and Experimental Design Five Hereford heifers (420 ± 6 kg, mean ± SD) were housed in 9 m2 pens equipped with rubber floor mats and individual water bowls and feeders at the Livestock Research Barn (University of Saskatchewan). Upon arrival, all heifers were treated for internal and external parasites with Ivomec (Merial Canada Inc., Baie d’Urfé, Quebec, Canada). The cattle were vaccinated against clostridial diseases with Covexin 8 (Schering-Plough, Kirkland, Quebec, Canada); Pasteurella haemolytica and Histophilus somni with Somnu-Star Ph (Novartis, Mississauga, Ontario, Canada); and infectious bovine rhinotracheitis, bovine viral diarrhea (types 1 and 2), parainfluenza type 3 virus, and bovine respiratory syncytial virus with Biostar, Starvac 4 Plus (Novartis, Mississauga, Ontario, Canada). After an acclimation period (6 wk), all heifers were spayed and fitted with a soft plastic rumen cannula (10 cm center diameter, Bar Diamond, Parma, ID).

Each heifer was assigned randomly to 1 of 5 treatments using a 5 × 5 Latin square design. The trial lasted 170 d, with 34-d periods. Each period consisted of 12 d for adaptation, 6 d (d 13 to 18) for voluntary intake, and 16 d (d 19 to 34) for collection. During the collection period, rumen fluid sampling was performed for 24 h (d 21), indwelling pH data were collected for 3 consecutive 23-h periods (d 25 to 27), and total fecal and urine collections were carried out during the remainder of the period for 5 consecutive days (d 29 to 34).

Treatments, Dietary Composition, and Feeding Heifers were individually fed a standard barley-based finishing ration (89% barley grain, 6% barley silage, and 5% supplement, DM) before the trial commenced. The treatments matched those of a performance trial reported previously (Walter et al., 2010). The DM in the control diet consisted of 88.7% rolled barley grain, 5.5% supplement, and 5.8% barley silage (Table 1). For the 4 DDGS treatments, wheat or corn DDGS was substituted for barley grain at either 20 or 40% of the dietary DM (Table 1). Rations were formulated to meet or exceed NRC (2000) requirements for CP, trace minerals, and vitamins A and D (Table 1). The Ca:P ratio was maintained in a range of 1.5:1 to 2:1 by supplementation with limestone as the DDGS content of the ration increased. The adaptation phase in each period consisted of 4 equal steps, each lasting 3 d, in which the concentrate (barley and wheat DDGS or corn DDGS) was increased or decreased by 5 or 10% at each step, depending on the target diet. All heifers had ad libitum access to fresh feed that was provided at 0800 and 1600 h each day. Before the morning feeding, feed bunks were swept clean, with orts removed, weighed, and recorded. To calculate voluntary intake as a percentage of BW, heifers were weighed on d 16 and 17 before feeding. On d 22, feed intake was restricted to 95% of ad libitum DMI and maintained at this amount throughout the rest of the period. Indwelling rumen pH probes were inserted on d 25, with data collection from d 25 to 27. After this, there was a 2-d rest period (d 28 and 29) before total collections ensued. Wheat DDGS was supplied by Noramera BioEnergy Corporation (Weyburn, Saskatchewan, Canada), whereas corn DDGS was purchased from ConAgra Foods (Omaha, NE). Barley grain (63.3 ± 0.6 kg/hL, mean ± SD) was purchased from a commercial grain source and dry rolled (RossKamp Champion, Waterloo, IA). The barley silage (AC Rosser) grown at the University of Saskatchewan was harvested and ensiled. Silage samples were taken every 2 wk, with the samples dried to determine DM content, which was used to adjust feeding amounts as necessary. For each mineralvitamin supplement, 1 batch was formulated and mixed to maintain consistency throughout the trial (Table 1).


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Table 1. Ingredient composition and analysis (% of dietary DM) of the control and dried distillers grains with solubles (DDGS)-based diets Wheat DDGS Item Diet composition  Barley silage  Barley grain  Wheat DDGS  Corn DDGS  Supplement Supplement composition  Barley  Canola meal  Canola oil  Urea  Limestone  Vitamin premix1  Ionophore premix2  Trace mineral salt Ration analysis3  OM  CP  Ether extract  ADF  NDF  ADIN  NDIN  Ca  P  GE, Mcal/kg

Control

Corn DDGS

20%

40%

20%

40%

5.8 88.7 — — 5.5

5.8 68.7 20.0 — 5.5

5.8 48.7 39.9 — 5.6

5.8 68.6 — 20.1 5.5

5.8 48.7 — 40.0 5.5

— 47.5 3.2 1.6 21.8 10.6 8.2 7.1

43.9 — — — 30.4 10.5 8.1 7.1

37.9 — — — 36.6 10.4 8.1 7.0

43.9 — — — 30.4 10.5 8.1 7.1

37.9 — — — 36.6 10.4 8.1 7.0

95.5 12.8 1.6 8.5 18.0 0.04 0.21 0.54 0.40 4.26

± ± ± ± ± ± ± ± ± ±

0.05 0.04 0.01 0.05 0.06 0.001 0.001 0.02 0.01 0.002

94.3 18.1 2.0 10.8 24.3 0.33 0.96 0.72 0.49 4.36

± ± ± ± ± ± ± ± ± ±

0.11 0.14 0.02 0.12 0.28 0.004 0.014 0.02 0.01 0.005

94.5 24.0 2.7 13.4 30.4 0.62 1.71 0.99 0.65 4.47

± ± ± ± ± ± ± ± ± ±

0.02 0.18 0.01 0.12 0.29 0.005 0.011 0.04 0.01 0.009

94.4 15.4 3.2 9.3 23.8 0.16 0.49 0.72 0.46 4.39

± ± ± ± ± ± ± ± ± ±

0.08 0.03 0.01 0.05 0.05 0.001 0.002 0.01 0.01 0.001

93.6 18.9 5.1 10.6 30.2 0.28 0.79 0.92 0.58 4.55

± ± ± ± ± ± ± ± ± ±

0.10 0.12 0.02 0.08 0.22 0.002 0.003 0.03 0.01 0.006

1

University of Saskatchewan (Saskatoon, Saskatchewan, Canada) vitamin A and D supplement = 440,500 IU of vitamin A and 88,000 IU of vitamin D3 per kilogram. 2 University of Saskatchewan Feed Unit Ionophore Premix contained 96.77% barley and 3.23% Rumensin Premix, containing monensin (as monensin sodium) at 200 g/kg (Elanco, Guelph, Ontario, Canada; DM basis). 3 Mean ± SE (n = 5).

Samples of each lot of DDGS, barley, and supplement were collected, and silage samples were taken every 2 wk for chemical analysis.

Rumen pH Measurement All heifers were fitted with indwelling rumen pH probes and data loggers using the Indwelling Continuous pH Measurement System (Dascor, Escondido, CA) described by Penner et al. (2006). The indwelling pH sensors allowed continuous monitoring (30-s measurement) of rumen pH in the ventral sac for 3 continuous 23-h periods. Every morning, between 0700 and 0800 h, the rumen pH probes were removed from the rumen and cleaned, the recorded data were downloaded, and the sensors were restandardized (pH 4 and 7). The pH data were averaged for each minute and summarized as minimum pH, mean pH, and maximum pH (SAS Inst. Inc., Cary, NC). The duration (min/d) and pH area (min/d × pH) under the curve were also calculated using thresholds (pH 5.8 to 5.5, pH 5.5 to 5.2, and pH 0.05) between treatments (Table 2). Similarly, no differences were observed (P > 0.05) in duration (min/d or min/ kg of OMI) or pH area (pH × min) below the critical pH cutoff values of 5.8 or 5.5. Cattle fed wheat DDGS, particularly at 20% inclusion, were more prone to rumen pH conditions attributed to acute acidosis. This was reflected in a quadratic response in greater pH area (P = 0.05) below pH 5.2 and trends in time spent below the pH cutoff value of 5.2, both in minutes per day (P = 0.07) and minutes per kilogram of OMI (P = 0.06; Table 2). Although feeding wheat DDGS had the most pronounced effect on rumen pH, it should be noted


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that all diets resulted in rumen fermentation conditions that, at a minimum, approached mild (pH