Evaluation of wheat-based wet distillers’ grains for feedlot cattle M. Ojowi, J. J. McKinnon1, A. Mustafa, and D. A. Christensen

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Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5B5. Received 4 November 1996, accepted 13 May 1997. Ojowi, M., McKinnon, J. J., Mustafa, A. and Christensen, D. A. 1997. Evaluation of wheat-based wet distillers’ grains for feedlot cattle. Can. J. Anim. Sci. 77: 447–454. This study was conducted to determine the nutritive value of wheat-based wet distillers’ grains (WDG) for ruminants. Chemical composition and in situ rumen degradability characteristics of WDG were compared with wet brewers’ grain (WBG). The in situ trial involved three 48 h incubations utilizing one ruminally fistulated cow. Trail 2 compared the value of WDG in growing and finishing rations relative to WBG and a control based on standard feed ingredients. Relative to WBG, WDG had greater (P < 0.05) NDF and ADL and similar ADF and CP levels. Fractionation of CP indicated that WDG contained more (P < 0.05) neutral detergent and less acid detergent insoluble CP than WBG. Effective degradability of DM, CP, NDF and ADF in WDG exceeded (P < 0.05) WBG. Animal performance in the growing period was similar (P > 0.01) among treatments. During the finishing period the control fed steers grew faster (P < 0.05) than WBG fed steers. WDG fed steers exhibited more (P < 0.05) intermuscular fat than control or WBG fed steers and less (P < 0.05) subcutaneous fat than WBG fed steers. It was concluded that WDG is more degradable than WBG and thus cannot be considered as good a source of rumen undegraded protein. WDG can be used effectively as an energy and protein source for growing and finishing cattle. Key words: distillers’ grains (wet), brewers’ grains (wet), rumen degradability, cattle, gain, carcass Ojowi, M., McKinnon, J. J., Mustafa, A. et Christensen, D. A. 1997. Évaluation de la valeur alimentaire des drèches de distillerie humides à base de blé pour les bovins en parc d’engraissement. Can. J. Anim. Sci. 77: 447–454. Nous avons examiné la valeur nutritive pour les ruminants des drèches de distillerie de blé fraîches (DDF). La composition chimique et la dégradation ruminale in situ des DDF étaient comparées avec celles des drèches de brasserie fraîches DBF. L’expérience in situ comportait 3 incubations de 48 h utilisant une vache munie d’une fistule ruminale. Dans une 2e expérience, on comparait la valeur des DDF dans les aliments de croissance et de finition par rapport aux DBF ainsi qu’à un aliment témoin fait d’ingrédients standards. Par rapport aux DBF, les DDF contenaient plus (P < 0,05) de FDN et de LDA et autant de lignocellulose et de PB. Le fractionnement de la PB révélait que les DDF contenaient plus (P < 0,05) de PB insoluble au détergent neutre et moins de PB insoluble au détergent acide que les DBF. La dégradabilité ruminale effective de m.s., de PB, de FDN et de lignocellulose des DDF dépassait (P < 0,05) celle des DBF. Les performances zootechniques observées durant la phase de croissance étaient les mêmes (P > 0,01) dans tous les traitements. Dans la phase de finition, la croissance des bouvillons exposés au régime témoin était plus rapide que chez ceux au régime DBF. Les bouvillons nourris aux drèches de distillerie possédaient plus (P < 0,05) de gras intermusculaire que ceux nourris au régime témoin ou DBF et aussi plus (P < 0,05) de gras sous-cutané que les bouvillons au régime DBF. Les drèches de distillerie paraissent être plus dégradables dans le rumen que les drèches de brasserie et, pour cette raison, ne peuvent être considérées comme une bonne source de protéines digestibles dans l’intestine. Elles constituent toutefois un aliment énergétique et protéique efficace pour les bouvillons en croissance et en finition. Mots clés: Drèches de distillerie fraîches, drèches de brasserie fraîches, dégradabilité dans le rumen, bovin, gain, carcasse

Excessive heat can, however, increase the unavailable protein content of distillers’ grains (Van Soest 1989). Distillers’ grains are also an excellent source of energy for ruminants. Several researchers have shown corn distillers’ grain to be superior to corn grain in energy value (Larson et al. 1993; Ham et al. 1994). The vast majority of the research relating to the feeding value of distillers’ byproducts is based on corn as the seed stock for fermentation. In western Canada, wheat is more likely to be utilized due to its availability. Boila and Ingalls (1994) have shown that, similar to corn, wheat-based DDG is a good source of RUDP and amino acids.

Whole stillage is the residual material following fermentation and distillation of cereal grains for fuel alcohol production. Whole stillage is composed of WDG and a liquid fraction called thin stillage or solubles (National Academy of Science–National Research Council (NAS–NRC) 1981). Marketing of distillers byproducts generally involves drying. Whole stillage can be dried to produce DDGS or fractionated into WDG and thin stillage. Drying of these byproducts results in DDG and dried distillers’ solubles, respectively (NAS-NRC 1981). Extensive research has been conducted on the feeding value of dried distillers’ byproducts (Firkins et al. 1984, 1985; Boila and Ingalls 1994; Ham et al. 1994). Heat applied during fermentation, distillation and drying reduces protein solubility and increases the RUDP content of the dried byproduct (Firkins et al. 1984; Boila and Ingalls 1994). 1Author

Abbreviations: ADF, acid detergent fiber; CP, crude protein; DDG, dried distillers’ grains; DDGS, dried distillers’ grains with solubles; DM, dry matter; DMI, dry matter intake; NDF, neutral detergent fiber; RUDP, rumen undegradable protein; WBG, wet brewers’ grain; WDG, wet distillers’ grains

to whom correspondence should be addressed. 447

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Distillers’ byproducts are dried to enhance shelf-life and transportation. However, drying is an energetically expensive process. Feeding distillers’ byproducts in wet form would significantly reduce the cost of processing and could enhance the development of integrated feedlot/fuel ethanol complexes. Larson et al. (1993) and Ham et al. (1994) have shown that corn-based WDG-fed cattle exhibited improved gains and feed efficiency relative to corn-fed cattle. The improved performance was attributed to a superior energy content of WDG relative to corn and to high RUDP levels (Larson et al. 1993; Ham et al. 1994). To the authors’ knowledge, no work has been published that defines the rumen degradability characteristics of wheat-based WDG or the performance of cattle fed this byproduct. Wet brewers’ grain a barley-based byproduct, is produced in a similar manner to WDG. Similar to WDG, nutrients other than starch are concentrated during fermentation and contribute to the digestible energy and protein content of WBG. Brewers’ grain has been classified as a feed source high in RUDP (Stern and Satter 1984; Cozzi and Polan 1994). WBG has been reported to be equal to or superior to soybean meal as a protein supplement for lactating dairy cows (Murdock et al. 1981; West et al. 1994) and has been utilized as an energy and protein supplement when available by selected feedlots in western Canada. These characteristics of WBG make it a good choice to use as a standard, to compare the nutritive value of wheat-based WDG. The objectives of this research were to define relative to barley-based WBG, the chemical composition and in situ nutrient degradability characteristics of wheat-based WDG. A second objective was to examine the performance and carcass characteristics of feedlot steers fed diets based on common feed ingredients for western Canada supplemented with wheat-based WDG or barley-based WBG. MATERIALS AND METHODS Chemical Composition of Wet Brewers’ and Wet Distillers’ Grain Samples of WBG (N = 5), supplied by the Great Western Brewing Company Limited of Saskatoon, Saskatchewan and WDG (N = 5) derived from wheat-based ethanol production supplied by the Pound-Maker Agventures Ltd., ethanol plant at Lanigan, Saskatchewan, were collected over the winter of 1991–1992. These samples were ground through a 1-mm screen and analyzed for moisture (method No. 930.15), ash (method No. 924.05), Kjeldahl nitrogen (method No. 984.13), ADF (method No. 973.18) and acid detergent lignin (method No. 973.18) according to the procedures of the Association of the Official Analytical Chemists (AOAC 1990). Neutral detergent fiber was determined according to the procedure of Van Soest et al. (1991). Total starch was determined using the α-amylase amyloglucosidase method (Megazyme kit, NSW, Australia). Neutral and acid detergent insoluble CP were determined on NDF and ADF residues, respectively, using the Kjeldahl method. Soluble crude protein was determined according to the procedure of Roe et al. (1990) and non-protein nitrogen was estimated using sodium tungstate as a precipitating agent (Licitra et al. 1996).

Total carbohydrate and protein contents of WBG and WDG samples were fractionated based on rumen degradability characteristics according to the Cornell Net Carbohydrate and Protein System (Sniffen et al. 1992). Total carbohydrate was fractionated into fraction A (rapidly degradable); fraction B1 (intermediately degradable); fraction B2 (slowly degradable) and fraction C (unavailable cell wall carbohydrate). Total CP was fractionated into fraction A (non-protein nitrogen), fraction B (true protein) and fraction C (unavailable protein). True protein was then sub-fractionated into B1 (highly degradable ), B2 (intermediately degradable) and B3 (slowly degradable) fractions (Sniffen et al. 1992). In Situ Nutrient Disappearance Trial One non-lactating Holstein cow fitted with a rumen cannula was utilized. The cow was fed a 50:50 barley silage:concentrate diet (DM basis) at 1.5% of body weight daily in two equal portions at 08:00 and 16:00 h. The diet contained (DM basis) 162, 374, 184, 7 and 6 g kg–1 CP, NDF, ADF, Ca and P, respectively. Equal portions of WBG and WDG from the five samples used for chemical analysis were pooled and ground through a 2-mm screen to obtain blended samples. Seven grams of WBG and WDG were weighed into duplicate nylon bags (9 × 21 cm, 41-mm pore size). The bags were then placed into polyester mesh bags (25 × 33 cm) and incubated in the rumen for 2, 4, 8, 12, 18, 24, 36 and 48 h. Three incubations were carried out. Each commenced prior to the morning feeding with bags inserted at the appropriate time, such that all were removed with bags incubated for 48 h. Following removal from the rumen, the bags were washed as described by McKinnon et al. (1991). Bags containing unincubated samples of WBG and WDG were washed at the same time to estimate zero hour disappearance. The washed bags were then dried in a forced-air oven at 65°C for 48 h and allowed to air equilibrate for 3 d. Contents of duplicate bags were composited and ground. Dry matter content was determined on the whole residues which were then subjected to Kjeldahl nitrogen, NDF and ADF analysis as described previously. The percent disappearance of DM, CP, NDF and ADF at each incubation time was calculated from the concentrations of these nutrients in the original samples and the residues and used to estimate ruminal kinetic parameters according to the equation of Ørskov and McDonald (1979) with the addition of a discrete digestion lag time (Khorasani et al. 1994): P = a + b(1–e-c(t-d)) Where P is rumen nutrient disappearance (g kg–1) at time t, a is the soluble fraction (g kg–1), b is the insoluble but degradable fraction (g kg–1), c is the rate of degradation (% h–1) of the b fraction and d is the lag time (h) before the start of degradation of the b fraction. Effective ruminal degradability (ED) was estimated using the equation of Ørskov and McDonald (1979), assuming rumen flow rate (k) of 5% h–1: ED = a + [(b × c)/(c + k)]

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OJOWI ET AL. — DISTILLERS GRAINS FOR FEEDLOT CATTLE

Feedlot Growth and Finishing Trial EXPERIMENTAL ANIMALS AND HOUSING. One hundred and twenty medium- frame yearling steers were purchased from commercial sources. The steers were fed and housed in outdoor pens at the University of Saskatchewan Beef Research Station at Saskatoon, Saskatchewan. The steers were managed according to the guidelines of the Canadian Council of Animal Care (1980). The cattle were adapted to feedlot conditions for 14 d prior to the start of the trial. The cattle with an average weight of 311 ± 24 kg (mean ± SD) were randomly allotted to 15 pens of 8 steers. Randomization was stratified to ensure a uniform weight across the 15 pens. EXPERIMENTAL DIETS AND FEEDING PROTOCOL. Each pen was assigned to one of the three dietary treatments. In the growing period, a control diet was formulated to 12.13 MJ DE kg–1 and 130 g kg–1 CP (DM basis). It consisted of barleybased concentrate, alfalfa/brome hay and barley straw (Table 1). Canola meal was used as a protein supplement. Diets were formulated using the following digestible energy (MJ DE kg–1 DM) and CP (g kg–1 DM) values for the chosen feed ingredients: barley grain 15.34 MJ kg –1 and 135 g kg–1; canola meal 12.94 MJ kg–1 and 380 g kg–1; wheat straw 8.04 MJ kg–1 and 60 g kg–1; alfalfa/brome hay 9.24 MJ kg–1 and 125 g kg–1; wet brewers’ grain 13.49 MJ kg–1 and 270 g kg–1; wet distillers’ grain 14.23 MJ kg–1 and 300 g kg–1. Digestible energy and crude protein values for barley and canola meal were average values for Saskatchewan (Anonymous 1990). All other values were derived from pretrial nutrient analysis carried out by Saskatchewan Feed Test Laboratory. The two treatment diets incorporated WBG and WDG, respectively and were formulated to the same energy and protein levels as the control diet. The WBG and WDG were obtained over the same time period and from the same sources as those used for the chemical analysis and the in situ trial. In the finishing phase, all three diets were formulated to a minimum of 120 g kg–1 CP and 14.2 MJ DE kg–1 (DM basis) (Table 2). All three diets fed during the growing and finishing period met the minimum crude protein levels set by the NAS–NRC (1984) for growing medium frame steers (Table 1 and 2). Data Collection and Analytical Procedure Each complete mixed ration was delivered to the steers by a feeder wagon, equipped with a mixing auger and a weigh scale. Orts were collected and weighed every 14 d. Data obtained were used to estimate DMI and feed conversion (kg feed kg –1 of gain) for each pen of cattle fed each treatment. Body weights of steers at the start and end of the growing and finishing periods were determined from the mean of two consecutive weights. During the remainder of the trial, body weight gain was determined from measurements taken every 2 wk. Complete mixed rations from feed bunks were collected throughout the trial and dried in a forced-air oven (60°C for 72 h). The samples were ground through a 1-mm screen and analyzed for moisture, Kjeldahl nitrogen, ADF and NDF as described previously. Ca and P levels were determined

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Table 1. Ingredient composition and chemical analysis of concentrate mixes and complete diets used in the growing period Dietary treatment Parameter

Control

WBG

WDG

815 154 11 20

968 – 11 21

968 – 11 21

Complete mixed diet (g kg–1 DM) Concentrate 590 Straw 300 Alfalfa/brome hay 110 Brewers’ grain – Distillers’ grain –

446 283 104 167 –

472 292 102 – 134

Chemical analysis of complete diet (g kg–1 DM) Dry matter 897 Crude protein 129 Acid detergent fiber 278 Neutral detergent fiber 466 Calcium 6 Phosphorus 4

608 138 279 500 7 5

709 131 271 499 7 4

Concentrate mix (g kg–1 DM) Barley Canola meal Limestone Mineral/vitamin/mixz

z The vitamin premix contained 440 040 IU vitamin A, and 88 009 vitamin D kg–1 premix. Trace minerals in the mineral premix were: 19% calcium,

19% phosphorus, 5025 ppm zinc, 413 ppm iodine, 188 ppm iron, 8025 ppm manganese, 3000 ppm copper and 100 ppm cobalt. Table 2. Ingredient composition and chemical analysis of concentrate mix and complete diets used in the finishing period Dietary treatment Parameter

Control

WBG

WDG

968 11 21

968 11 21

968 11 21

Complete mixed diet (g kg–1 DM) Concentrate 930 Straw 70 Brewers’ grain – Distillers’ grain –

885 58 57 –

866 87 – 47

Chemical analysis of complete diet (g kg–1 DM) Dry matter 896 Crude protein 128 Acid detergent fiber 115 Neutral detergent fiber 300 Calcium 5 Phosphorus 4

801 140 113 271 5 4

840 136 139 276 6 4

Concentrate mix (g kg–1 DM) Barley Limestone Mineral/vitamin/mixz

zThe vitamin premix contained 440 040 IU vitamin A, and 88 009 vitamin D kg–1 premix. Trace minerals in the mineral premix were: 19% calcium, 19% phosphorus, 5025 ppm zinc, 413 ppm iodine, 188 ppm iron, 8025 ppm manganese, 3000 ppm copper and 100 ppm cobalt.

using an atomic absorption spectrophotometer (Zazoski and Burau 1977). Cattle were targeted for slaughter on the basis of equal subcutaneous fat (8 mm) as determined by ultrasound (Bergen et al. 1996). Carcass data were obtained on all animals through Agriculture Canada’s Blue Tag program. The left side of each carcass was “ribbed” the morning after slaughter between the 12th and 13th ribs. Measurements

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taken on the exposed surface of the longissimus dorsi included thickness of the subcutaneous fat cover (measured at a minimum point of thickness in last quadrant), longissimus dorsi area, cutability (lean %) and marbling score. Four randomly selected animals pen–1 were used to examine the effects of treatment on rib muscle, fat and bone composition. A commercial seven-bone rib was obtained from the carcass of each selected animal at slaughter and dissected according to the procedure of McKinnon et al . (1993). Statistical Analysis Data from the chemical composition and the in situ studies were analyzed as a completely randomized design using the General Linear Model (GLM) procedure of the SAS Institute, Inc. (1989). Means were separated at the 5% level of significance using the Student-Newman-Keuls Procedure (Steel and Torrie 1980). Feedlot data were analyzed as a completely randomized design. Pen was used as the experimental unit. Single degree of freedom contrasts were used to compare treatment effects on feedlot performance and carcass composition (Steel and Torrie 1980). Differences among contrasts were considered significant if P values were ≤0.05. Contrasts of interest were: A = control versus WBG; B = control versus WDG; C = WBG versus WDG.

Table 3. Ash and ether extract concentrations and carbohydrate fractions (mean ± SD) of WBG and WDG (DM basis) WBG (N = 5)

WDG (N = 5)

SEMz

Ash

42.0 ± 4.4a

27.0 ± 1.7b

1.5

Ether extract

76.0 ± 9.1

66.0 ± 7.6

3.8

641.0 ± 20.2b 241.0 ± 7.9

749.0 ± 26.7a 241.0 ± 12.3

10.6 4.6

78.0 ± 3.5b 28.0 ± 6.6a

104.0 ± 10.3a 15.0 ± 5.3b

4.1 2.7

47.0 ± 14.3b 576.0 ± 20.9a 598.0 ± 14.0b

71.0 ± 4.5a 171.0 ± 32.5b 641.0 ± 23.6a

4.7 66.9 8.6

Carbohydrate fractions (g kg–1 DM) A 19.0 ± 17.1 B1 25.4 ± 6.1a B2 431.0 ± 32.6 C 124.0 ± 22.5b

17.0 ± 8.1 3.2 ± 2.4b 438.0 ± 20.2 187.0 ± 24.7a

6.0 2.1 12.1 10.6

kg–1)

Carbohydrate analysis (g Neutral detergent fiber Acid detergent fiber Acid detergent lignin (g kg-1 of NDF) Starch Nonstructural carbohydrate (NSC) Starch (g kg-1 of NSC) Total carbohydrate

zSEM

= pooled standard error of the mean. a, b Means in the same row followed by different letters are different (P < 0.05).

Table 4. Protein fractions (mean ± SD) of WBG and WDG (DM basis) WBG (N = 5)

WDG (N = 5)

SEMz

284.0 ± 14.2

264.0 ± 39.6

0.87

Buffer soluble protein (g kg–1of CP) Total soluble protein 106.0 ± 23.3b Non-protein nitrogen (fraction A) 87.0 ± 22.9 Soluble true protein 19.0 ± 7.0b

249.0 ± 20.1a 61.0 ± 21.9 187.0 ± 33.1a

1.46 10.0 10.7

471.0 ± 51.0a

16.6

59.0 ± 4.5b

5.6

880.0 ± 20.9a 187.0 ± 33.1a 280.0 ± 50.9b 413.0 ± 48.9a

11.4 10.7 18.6 15.8

RESULTS AND DISCUSSION Chemical Composition of Wet Brewers’ and Wet Distillers’ Grain The chemical profile of WBG reported in this study is in good agreement with literature values (Sniffen et al. 1992; Van Soest et al. 1992; West et al. 1994). The DM content of WBG and WDG averaged 227 ± 23 and 294 ± 22 g kg–1, respectively. Relative to WBG, the wheat-based WDG had similar ADF and higher (P < 0.05) NDF and acid detergent lignin values (Table 3). As expected, starch levels were low in both byproducts, however, WDG exhibited lower (P < 0.05) values than WBG (Table 3). Total carbohydrate levels were greater (P < 0.05) for WDG than WBG. Fractionation of the total carbohydrate showed similar levels of highly soluble (fraction A) and available cell wall (fraction B2) carbohydrate. However, the intermediately degradable fraction (fraction B1) was higher in WBG than WDG. In contrast, the unavailable carbohydrate fraction (fraction C) was higher (P < 0.05) in WDG (Table 3). Crude protein and non-protein nitrogen (g kg–1 of CP) levels were similar in both byproducts (average 274 and 74 g kg–1, respectively, Table 4). However, WDG contained more (P < 0.05) soluble CP and neutral detergent insoluble CP and less (P < 0.05) acid detergent insoluble CP than WBG (Table 2). Boila and Ingalls (1994) reported higher CP and lower NDF and ADF levels for wheat-based dried distillers’ grain than the values reported in the present study. This was likely due to the fact that distillers’ grain samples used in their study was a combination of dried distillers’ grains and dried distillers’ solubles. In the present study, the soluble material known as thin stillage was removed by the ethanol plant from the WDG by screening and pressing, prior to feeding. Ojowi (1995) showed that wheat-based thin

Crude protein (CP, g

kg–1)

Cell wall protein (g kg–1 of CP) Neutral detergent insoluble protein 306.0 ± 12.2b Acid detergent insoluble protein (fraction C) 125.0 ± 17.2a True protein fractions (g kg–1 of CP) Total (fraction B) 789.0 ± 29.5b B1 (rapidly degradable) 19.0 ± 7.0b B2 (intermediately degradable) 586.0 ± 29.2a B3 (slowly degradable) 179.0 ± 10.9b zSEM

= Pooled standard error of the mean. a, b Means in the same row followed by different letters are different (P < 0.5).

stillage had higher CP and lower NDF and ADF levels than WDG. Total true protein was less (P < 0.05) in WBG than WDG (Table 4). This was due to the higher (P < 0.05) acid detergent insoluble CP level in WBG. Rapidly (B1 fraction) and slowly (B3 fraction) degradable true protein were greater (P < 0.05) in WDG than WBG (Table 4). However, WBG contained more (P < 0.05) intermediately degradable true protein (B2 fraction) (Table 4). The values reported in this study for WBG were consistent with those reported by Sniffen et al. (1992). No comparable literature values are available for WDG from wheat-based fermentation, however, they are similar to those reported for wet corn distillers’ grain (Sniffen et al. 1992).

OJOWI ET AL. — DISTILLERS GRAINS FOR FEEDLOT CATTLE

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Table 5. In situ nutrient rumen kinetic parameters and effective degradability of WBG and WDG (DM basis) WBG

WDG

SEM

Dry matter Soluble (g kg–1) Degradable (g kg–1) Degradation rate (% h–1) Lag time (h) Effective degradabilityz (g kg–1)

238.0 486.0b 5.3a 1.5 487.0b

251.0 605.0a 4.1b 1.7 524.0a

12.7 20.6 0.22 0.23 8.9

Neutral detergent fiber Soluble (g kg–1) Degradable (g kg–1) Degradation rate (% h–1) Lag time (h) Effective degradabilityz (g kg–1)

137.0b 518.0b 4.5a 3.8a 383.0b

204.0a 749.0a 2.7b 2.4b 463.0a

6.1 11.6 0.09 0.22 6.3

Acid detergent fiber Soluble (g kg–1) Degradable ( g kg–1) Degradation rate (% h–1) Lag time (h) Effective degradabilityz (g kg–1)

97.0 511.0b 2.7 7.0a 275.0b

113.0 865.0a 1.6 5.6b 319.0a

5.4 62.4 0.35 0.30 5.5

Crude protein Soluble (g kg–1) Degradable (g kg–1) Degradation rate (% h–1) Lag time (h) Effective degradabilityz (g kg–1)

265.0b 460.0 5.9b 3.5a 549.0b

371.0a 502.0 8.8a 1.0b 691.0a

6.3 23.0 0.67 0.44 10.4

a, bMeans in the same row followed by different letters are different (P < 0.05). zCalculated assuming 5% h–1 rumen flow rate.

In Situ Nutrient Disappearance Trial In situ soluble DM was similar (P > 0.05) in WBG and WDG (Table 5). However, WBG had lower (P < 0.05) potentially degradable DM and a higher (P < 0.05) rate of degradation of potentially degradable DM than WDG. As a result, effective DM degradability was greater (P < 0.05) in WDG than in WBG (Table 5). Boila and Ingalls (1994) reported ruminal DM kinetic parameters and effective degradability for wheat-based dried distillers’ grain similar to those found in this study for WDG. Soluble CP and rate of degradation of potentially degradable CP and effective CP degradability were higher (P < 0.05) in WDG than WBG (Table 5). However, potentially degradable CP was similar in both byproducts (average 481 g kg–1). The lower rumen degradability of WBG can be attributed to its higher acid detergent insoluble CP content relative to WDG. High levels of acid detergent insoluble CP have been shown to reduce ruminal DM (Moshtaghi Nia and Ingalls 1992) and CP (Boila and Ingalls 1994; Mustafa et al. 1997) degradability of heat-treated protein supplements. Boila and Ingalls (1994) reported a lower effective CP degradability (488 g kg–1) for wheat-based dried distillers’ grain than that reported in this study (691 g kg–1; Table 5). The difference is likely a result of the heat applied during the drying process to obtain DDGS used in the Boila and Ingalls (1994) study. Supplemental heating would explain the smaller soluble CP fraction (226 g kg–1) and the slower rate of degradation of the potentially degradable CP fraction

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(2.6% h–1) reported by Boila and Ingalls (1994) for DDGS relative to WDG reported in the present study. Other researchers have reported similar effects of heat treatment on other protein supplements (Mir et al. 1984; Mustafa et al. 1997). These results suggest that wheat-based WDG would not be classified as a good source of RUDP. Wet distillers’ grain had more soluble and potentially degradable NDF than WBG (Table 5). The rate of degradation of the potentially degradable fraction was higher (P < 0.05) for WBG than for WDG. Varga and Hoover (1983) reported that protein sources such as distillers’ and brewers’ grains have relatively rapid rates of NDF degradation. Lag phase for NDF digestion was longer (P < 0.05) for WBG than for WDG, consequently, effective NDF degradability was higher (P < 0.05) for WDG than for WBG. This finding is somewhat surprising in that chemical fractionation of the total carbohydrate content indicated that WDG has a higher unavailable carbohydrate fraction (Fraction C) than WBG (Table 3). Varga and Hoover (1983) also reported higher ruminal NDF degradability for corn-based distillers’ grain than brewers’ grain. Larson et al. (1993) suggested that the high digestibility of the NDF fraction of distillers’ grain is likely due to cellulolytic effects of yeast fermentation. Soluble ADF and rate of degradation of the potentially degradable ADF was similar in WBG and WDG (Table 5). However, effective ADF degradability and potentially degradable ADF were higher (P < 0.05) in WDG (Table 5). These results indicate that the fiber components of WDG are more degradable than those of WBG. They also indicate that the higher DM degradability of WDG relative to WBG was due to higher CP, NDF and ADF degradability. Feedlot Growth and Finishing Trial In commercial feedlots, byproduct feeds such as WBG or WDG would be incorporated into diets formulated to set energy and protein levels consistent with targeted performance levels for growing or finishing cattle. As such, the diets used in this trial were formulated to be isonitrogenous and isocaloric in both the growing and finishing periods. However, since energy and protein levels differed between feed ingredients of interest (i.e. WBG, WDG and barley) it was necessary to formulate diets with varying ratios of roughage and concentrate. No treatment effects were observed in weight gain and DMI over the course of the growing period (Table 6). Differences were noted, however, at intermediate stages of the growing period (data not shown). For example, the cattle fed the WDG gained faster (P < 0.05) than the control steers (1.57 vs. 1.41 kg–1 d) through day 56 of the growing phase. The WBG fed cattle were intermediate (1.53 kg–1 d). These differences disappeared by day 84 of the trial (Table 6). Steers fed WBG tended (P < 0.10) to have better feed conversions than steers fed the canola meal based control. This may have resulted from improved metabolizable protein status of the cattle fed the WBG diet. The in situ results (Table 5) indicate that WBG has a lower effective in situ protein degradability relative to WDG, which in turn

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Table 6. Performance of cattle fed WBG and WDG or the control diet Contrasts (P>F)z

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Treatment Control

WBG

WDG

SEMy

Growing period (day 1–84) Initial weight (kg) Final weight (kg) Days on feed Dry matter Intake (kg d–1) Feed Conversion Average daily gain (kg d–1)

313.70 420.80 84.00 9.47 7.50 1.26

309.20 424.60 84.00 9.12 6.80 1.36

310.10 424.70 84.00 9.71 7.20 1.35

2.13 3.60 – 0.28 0.30 0.05

Finishing period (day 84–slaughter) Initial weight (kg) Final weight (kg) Days on feed Dry matter Intake (kg d–1) Feed Conversion Average daily gain (kg)

420.80 513.50 66.60 10.47 7.53 1.40

424.60 506.80 66.00 10.06 8.07 1.25

424.70 505.70 61.50 10.91 8.32 1.32

3.60 3.90 – 0.41 0.45 0.05

Overall (day 1 – slaughter) Start of test weight (kg) End of test weight (kg) Days on feed Daily gain (kg) Dry matter intake (kg d–1) Feed conversion

313.70 513.50 151.60 1.32 9.96 7.60

309.20 506.80 151.00 1.31 9.59 7.30

310.10 505.70 146.50 1.34 10.30 7.70

2.13 3.90 2.40 0.03 0.32 0.30

zContrasts of interest: A = control vs. wet brewers ySEM = pooled standard error of the mean.

A

B

C

0.10

0.05

grain, B = control vs. wet distillers grain, C = wet brewers vs. wet distillers grain.

was similar to literature values for canola meal (Boila and Ingalls 1992; Mustafa et al. 1997). As a result, higher levels of RUDP should reach the small intestine of WBG fed cattle. Studies have shown that cattle supplemented with RUDP sources have shown improved performance, particularly young growing calves (Veira et al. 1988; Reddy and Morrill 1993). During the finishing period, cattle fed the control diet gained faster (P = 0.05) than those fed the WBG based diet (Table 6). The most probable explanation for this observation is that the control cattle benefited from compensatory growth due to their relative poor performance during the growing phase. The poor performance of the WBG fed cattle was evident throughout the finishing period (data not shown). By day 42 both the control (1.39 kg d–1) and the WDG fed (1.39 kg d –1) cattle were gaining faster (P < 0.05) than the WBG fed cattle (1.23 kg d–1). No significant differences were noted in feed intake or in feed conversions during the finishing period although the control animals were numerically the most efficient group. When the performance of cattle fed the three dietary treatments was compared for the total period, there was no influence of treatment on overall growth rate, feed intake or conversion efficiency (Table 6). The results of the current study differ somewhat from those that used corn-based WDG, in that gain and feed conversion efficiency were improved with the corn-based products (Ham et al. 1982; Larson et al. 1993). The difference is likely due to the fact that in the corn work, diets were formulated such that WDG was substituted for corn grain on a 1:1 dry matter basis. Consequently, the diets containing the distillers’ byproducts were higher in energy than the corn grain-based diet. In the present study, diets were formulated to equal energy and protein levels. The

results of this feeding trial do, however, indicate that diets based on WDG from wheat-based ethanol production will support growth at levels equal to or in excess of those found with diets based on wet brewers’ grains or the standard ingredients used in the control diet. Carcass traits collected at slaughter (Table 7) did not differ among treatments. Similarly, few differences were noted in rib composition with the exception that WDG fed cattle exhibited higher (P < 0.05) levels of intermuscular fat relative to both WBG and control fed cattle and WBG fed cattle had a higher (P < 0.02) level of subcutaneous fat than the WDG fed cattle (Table 7). No apparent reason is evident for these differences in fat partitioning. These results, however, indicate that carcass quality traits will be similar for cattle fed WDG relative to cattle fed diets based on the common feed ingredients used for the control cattle. Hanke and Lindor (1982) observed similar results for cattle fed cornbased WDG relative to those fed high moisture corn and urea. CONCLUSIONS Results of the in situ trial indicate that wheat-based WDG is more degradable than WBG. This is supported by the chemical analysis of the two byproducts which shows that WBG has a higher level of acid detergent insoluble protein. The higher effective NDF degradability of WDG relative to WBG indicates that WDG is a superior source of fermentable fiber for ruminants. In the feeding trial, cattle fed diets incorporating wheat-based WDG exhibited performance at least equal to that from cattle fed the control or WBG diets during the growing and finishing periods. No adverse effects were seen on carcass composition. Based on this work it can be concluded that wheat-based WDG is a

OJOWI ET AL. — DISTILLERS GRAINS FOR FEEDLOT CATTLE

453

Table 7. Carcass characteristics and composition of cattle fed the control, WBG or WDG diet Contrasts (P>F)z

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Treatment Control

WBG

WDG

SEMy

273.60 55.10 74.60 59.90 7.50 1.10

269.40 55.00 72.90 59.20 7.90 1.20

269.90 55.10 74.20 59.50 8.00 1.20

3.00 0.30 1.50 0.30 0.30 0.06

Rib composition Bone (%) Lean (%) Fat (%)

21.50 53.60 24.90

21.40 54.10 24.40

21.40 54.40 24.20

0.30 0.70 0.70

Fat partitioning Intermuscular fat (%) Subcutaneous fat (%) Body cavity fat (%)

51.00 36.20 12.80

50.80 37.50 11.70

52.80 34.70 12.40

0.30 0.60 0.50

Carcass characteristics Weight (kg) Dressing (%) Ribeye area (cm2) Cutability (%) Average fat (mm) Marbling scorex

z Contrasts of interest: A = control vs. wet brewers y SEM = pooled standard error of the mean. xMarbling score 1 = trace; 2 = slight; 3 = small.

A

B

0.01 0.02

0.01

C

grain, B = control vs. wet distillers grain, C = wet brewers vs. wet distillers grain.

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