Brewing by-products: their use as animal feeds

Vet Clin Food Anim 18 (2002) 233–252

Brewing by-products: their use as animal feeds Michael L. Westendorf, PhD*, James E. Wohlt, PhD Department of Animal Sciences, Cook College, The State University of New Jersey—Rutgers, New Brunswick, NJ, 08901 USA

Brewers grains, often referred to as spent grains, have been fed to livestock since the advent of beer production. They consist largely of structural carbohydrates (cellulose, hemicellulose) and the protein remaining when barley is malted and mashed to release sugars for brewing. The primary by-products produced from the brewing process are brewers condensed solubles (produced from the mechanical dewatering of brewers grains), brewers yeast (which remains after brewing sugars have been converted to alcohol), and brewers grains [1]. Brewers grains, because of the removal of sugars and starches during the malting and mashing process, are higher in fiber (cell-wall carbohydrates), protein, and some minerals than are the foundation grains. Brewers grains have been fed to cattle, horses, pigs, and sheep, and solubles have been incorporated into poultry rations [1,2]. Currently, the primary market for wet brewers grains is as a dairy cattle feed; however, some may be fed to beef cattle in feedlots. Brewers grains have historically been marketed wet or dry, but wet brewers grains make up the majority of the marketed product. Larger breweries have the ability to separate different by-products (brewers grains, brewers yeast, brewers condensed solubles); smaller microbreweries will also produce spent grains. These smaller microbreweries do not have the ability to segment products and may discard some of the by-products. Many of these either market or give wet brewers grains to dairy or beef producers. This review focuses on the use of brewers grains as livestock feed and discusses the manner in which they are produced, their nutrient content, their suitability as livestock feed, the future of their use, and any implications on animal health when feeding.

* Corresponding author. E-mail address: [email protected] (M.L. Westendorf). 0749-0720/02/$ - see front matter Ó 2002, Elsevier Science (USA). All rights reserved. PII: S 0 7 4 9 - 0 7 2 0 ( 0 2 ) 0 0 0 1 6 - 6

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Background In a 1956 review, Morrison [3] indicated that brewers grains were fed chiefly to dairy cattle. They have been used primarily as a protein source, but have also been used to replace concentrate feeds in rations for dairy and beef cattle, sheep, swine, and horses. Wet brewers grains [2,3], because of their thin, wet, perishable nature, were usually fed on farms located near breweries to minimize the occurrence of spoilage. Morrison [3] recommended dried brewers grains as a concentrate replacement for livestock. Up to one third of the concentrate mixture can be replaced with dried brewers grains when fed to dairy cows. Fattening lambs have been fed mixtures of one third brewers grain and two thirds shelled corn, and calves have been fed up to 3 lbs. per head daily as a substitute for soybean meal and corn. Morrison [3] indicated that dried brewers grains were less palatable than other feeds, but that they could be incorporated as a part of the concentrate feed when lower in price than grain. According to an industry source (Bill Cromie, Commodity Specialists Co., Sarasota, FL, personal communication, 2001), dried brewers grains are declining in use as a feedstuff, while wet brewers grains are being increasingly used as feed. There are several reasons for this. First, high costs of drying favor the production of wet brewers grains. Second, there is an increased demand for wet brewers grains, particularly as a dairy feed. Third, the seasonality of beer production results in a situation in winter months where nearly all spent grains must be marketed as wet brewers grains to meet demand, making the maintenance of drying facilities less economical. Finally, the ability to transport and feed wet brewers grains in a timely manner is much improved from the past. Henry and Morrison [2] indicated that wet grains were often spoiled at the time of feeding and sometimes were the exclusive feedstuff in the diet. These wet brewers grains were usually used as feed near breweries. Improvements in transport and management have improved the usefulness of wet brewers grains. Cromie (personal communication, 2001) estimates that 50,000 to 100,000 tons of dried brewers grains are marketed in the United States annually. Anheuser-Busch Company currently has two breweries that produce dried brewers grains (Newark, NJ and Williamsburg, VA), and Coors has one (Golden, CO). Because of their low energy content, dried brewers grains are not usually fed to swine [3] but can make an economical substitute when fed to horses as a replacement for oats. Cunha [4] indicated that dried brewers grains are a good source of protein and can be a good feed for horses, supplying bulk to the diet and making an excellent component of complete feeds. Wet brewers grains [3] are primarily fed to cattle, although Henry and Morrison [2] indicated that they can be fed to fattening swine, horses, and sheep. The ‘‘washy’’ or high-moisture nature of wet brewers grains makes them a less useful feed for swine or horses, although Cunha [4] reported that they have been fed to horses provided spoilage concerns are managed.

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Brewers grains can be compared with a variety of other by-products such as wheat bran, wheat middlings, beet pulp, citrus pulp, rice bran, hominy feed, corn gluten feed, corn gluten meal, soy hulls, and distillers grains.

Production of brewers grains To understand brewers grain production it is helpful to first understand the brewing process. This process combines malted barley, corn grit, rice, and hops in producing beer, and results in the production of brewers grains and other by-products. In the production of beer, barley is first malted (germinated) by soaking it in warm water for 2 to 3 days. In the presence of malting enzymes starches are converted to sugar. After sprouting is complete, the grain is dried and the malting by-products are removed. The malted grain is crushed, water is added, and the mixture is heated. Heating promotes enzymatic action and the conversion of starch to sugar. This is referred to as mashing. Additional grains, corn grits, and rice are added to the mash. Mashing or cooking proceeds until most of the starch has been converted to sugar. This mash is sparged, pressed, and centrifuged, yielding spent grains, brewers grains, and a liquid called wort. Hops are added to the wort, and then the mixture is boiled and filtered to remove residual hops. Yeast culture is added to the wort, which is very high in sugars, and fermentation begins. The fermented wort becomes beer. The yeast developing in the fermentation process is removed and dried and can be sold as brewers yeast. Fig. 1 gives an outline of this process. The chief by-products are malt hulls, malt sprouts, malt cleanings, brewers grains, hops, dried brewers yeast, and brewers condensed solubles. Fig. 1 also shows where the by-products are removed during the brewing process. Sometimes, commercially marketed brewers grains may contain other fractions from the brewing process. For example, malt and hop by-products may be included as components of dried or wet brewers grains. More information on feed definitions can be obtained from the Association of American Feed Control Officials [5]. Table 1 describes AAFCO feed definitions for by-products from the brewing process. Table 2 lists nutrient values for several of the by-products given in Table 1. Those interested in more information on the brewing process and the various by-products should refer to Brewing [6] or Livestock Feed Resources and Feed Evaluation in Europe [7].

Nutrient content of brewers or spent grains Tables 3 through 7 summarize recent databases for the nutrient content of dry and wet brewers grains. The reported average nutrient composition

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Fig. 1. Brewing process.

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Table 1 Official definitions for brewing byproducts (AAFCO, 2001) 15.1 Brewers dried grains are the dried extracted residue of barley malt alone or in mixture with other cereal grain or grain products resulting from the manufacture of wort or beer and may contain pulverized dried spent hops in an amount not to exceed 3%, evenly distributed. (Adopted 1965, amended 1972.) IFN 5-00-516 Barley brewers grains dehydrated 15.2 Malt sprouts are obtained from malted barley by the removal of the rootlets and sprouts which may include some of the malt hulls, other parts of malt, and foreign material unavoidably present. It must contain not less than 24% crude protein. The term malt sprouts, when applied to a corresponding portion of other malted cereals, must be in a qualified form: ie, ‘‘Rye Malt Sprouts,’’ ‘‘Wheat Malt Sprouts,’’ etc. (Adopted 1942, amended 1964, 1980.) IFN 5-00-545 Barley malt sprouts dehydrated IFN 5-04-048 Rye malt sprouts dehydrated IFN 5-29-796 Wheat malt sprouts dehydrated 15.3 Malt cleanings are obtained from the cleaning of malted barley or from the recleaning of malt that does not meet the minimum crude protein standard of malt sprouts. It must be designated and sold according to its crude protein content. (Adopted 1942.) IFN 5-00-544 Barley malt cleanings dehydrated 15.4 Malt hulls consist almost entirely of hulls as obtained in the cleaning of malted barley. (Adopted 1942.) IFN 1-00-497 Barley malt hulls 15.5 Dried spent hops are obtained by drying the material filtered from hopped wort. (Adopted 1944.) IFN 5-00-396 Hop common fruit (hops) spent dehydrated 15.6 Brewers wet grains are the extracted residue resulting from the manufacture of wort from barley malt alone or in mixture with other cereal grains or grain products. The guaranteed analysis should include the maximum moisture. (Proposed 1971, adopted 1974.) IFN 5-00-517 Barley brewers grains wet 15.7 Brewers condensed solubles are obtained by condensing liquids resulting as byproducts from manufacturing beer or wort. It must contain not less than 20% total solids and 70% carbohydrates on a dry matter basis, and the guaranteed analysis shall include maximum moisture. (Proposed 1975.) IFN 5-12-239 Barley brewers soluble condensed 96.4 Brewers dried yeast are the dried, nonfermentative, nonextracted yeast of the botanical classification Saccharomyces resulting as byproduct from the brewing of beer and ale. It must contain not less than 35% crude protein. It must be labeled according to its crude protein content. (Adopted 1955, amended 1975, adopted 1978.) IFN 7-05-527 Yeast brewers dehydrated 96.10 Brewers liquid yeast are the nonfermentative, nonextracted yeast of the botanical classification Saccharomyces resulting as a byproduct from the brewing of beer and ale. It must contain not less than 35% crude protein on a dry weight basis. The guaranteed analysis shall include the maximum moisture. (Proposed 1976, adopted 1978.) IFN 7-20-878 Yeast brewers liquid

92.0 21.0 93.0 94.0 93.0

60.0 66.0 79.0 71.0 32.0

TDN (%) 0.68 0.68 0.83 0.74 0.30

NEL (Mcal/lb.) 25.4 25.4 46.9 28.1 24.8

CP (%) 6.5 6.5 0.9 1.4 5.1

EE (%) 24.0 23.0 4.0 18.0 30.0

ADF (%)

4.8 4.8 7.1 6.7 6.0

Ash (%)

0.33 0.33 0.13 0.26 –

Ca (%)

From Bath D, Dunbar J, King J, Berry S, Olbrich S. Byproducts and unusual feedstuffs. In: Feedstuffs 2001;73(29):30–7; with permission [47].

DM (%)

Byproduct

Dried brewers grains Wet brewers grains Brewers dried yeast Malt sprouts Dried spent hops

Table 2 Nutrient analysis of brewing byproducts (Bath et al., 2001)

0.55 0.55 1.49 0.84 –

P (%)

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Table 3 Wet brewers grain analysis completed by the DairyOne Forage Laboratory in Ithaca, NY, between 1998 and 2001 Nutrient

N

Unit

Mean

Range

SD

DM CP Deg. CP Sol. CP ADF NDF ADF-CPa NDF-CPb TDN NEL NEM NEG NSC Lignin Ash Fat Ca P Mg K Na Fe Zn Cu Mn Mo S Cl) Ion

1424 1038 124 466 777 783 14 48 779 779 779 779 779 163 188 357 595 595 595 595 301 301 301 301 301 301 250 15

% % % of CP % of CP % % % % % mcal/lb mcal/lb mcal/lb % % % % % % % % % ppm ppm ppm ppm ppm % %

23.2 29.0 30.6 10.7 23.3 47.9 3.22 9.43 74.1 0.81 0.82 0.53 11.1 6.54 4.47 8.60 0.35 0.68 0.23 0.16 0.04 207 97 8.34 50.3 2.72 0.33 0.08

18.5–28.9 24.8–33.6 23.1–40.3 4.3–17.1 20.7–28.8 41.4–55.2 1.01–5.43 5.41–12.89 71.4–76.7 0.77–0.84 0.76–0.88 0.49–0.58 2.8–17.8 4.8–8.3 3.7–5.6 7.50–10.10 0.18–0.53 0.57–0.78 0.17–0.29 UP TO 0.38 UP TO 0.14 27–361 76–118 1.0–17.0 37–63 1.8–3.7 0.27–0.39 0.01–0.17

4.6 4.2 8.5 6.3 2.9 6.1 2.21 2.80 2.5 0.03 0.05 0.04 6.6 1.53 0.65 1.16 0.16 0.09 0.05 0.21 0.08 146 20 6.5 12.4 0.80 0.06 0.08

Abbreviations: DM, dry matter; CP, crude protein; Deg. CP, degradable crude protein; Sol. CP, soluble crude protein; ADF, acid detergent fiber; NDF, neutral detergent fiber; TDN, total digestible nutrients; NEL, net energy for lactation; NEM, net energy for maintenance; NEG, net energy for gain; NSC, nonstructural carbohydrates; Ca, calcium; P, phosphorous; Mg, magnesium; K, potassium; Na, sodium; Fe, iron; Zn, zinc; Cu, copper; Mn, manganese; Mo, molybdenum; S, sulfur; Cl) Ion, chloride. a CP present in the ADF residue. b CP present in the NDF residue. Data provided courtesy of Mr. Paul Sirois, DairyOne Forage Laboratory, Ithaca, NY.

of grains from these databases represents large numbers of samples, grains produced in different regions of the US (Table 3, Northeast; Tables 4 and 5, De Peters et al [8], California), grains produced by major commercial breweries (Table 6), and grains produced by microbreweries (Table 7). All data, irrespective of where grains were produced or by what brewery (Tables 3–7), indicate that brewers grains are composed primarily of two nutrient constituents, crude protein (CP) [25% of grain dry matter (DM)] and neutral detergent fiber (NDF) (50% of grain DM). Surprisingly

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Table 4 A comparison of wet and dry brewers grains nutrient analysis taken from two recent reviews NRC, 2001 [10] Nutrient DM CP Avail. CP Unavail. CP Sol. CP ADF NDF ADF-CPa NDF-CPb TDN NEL NEM NEG Fat NSC Lignin Ash Ca P Mg K Na Fe Zn Cu Mn Mo Se S Cl) Ion

Units % % % % % of CP % % % % % mcal/lb mcal/lb mcal/lb % % % % % % % % % ppm ppm ppm ppm ppm ppm % %

dry

wet

90.7 (3.5) 29.2 (4.0)

21.8 (5.0) 28.4 (4.0)

22.2 (3.9) 47.4 (6.6) 9.1 (3.7) 3.5 (0.9) 71.3 0.78 0.84 0.55 5.2 (1.6)

23.1 (3.8) 47.1 (6.8) 9.3 (3.9) 2.9 (0.9) 71.6 0.78 0.84 0.55 5.2

5.0 (2.7) 4.3 (0.9) 0.30 (0.11) 0.67 (0.06) 0.26 (0.35) 0.50 (0.26) 0.04 (0.06) 224 (119) 85 (15) 11 (6) 45 (12) 3.2 (0.8) 1.06 (0.28) 0.38 (0.8) 0.07 (0.02)

4.7 (0.9) 4.9 (1.1) 0.35 (0.22) 0.59 (0.10) 0.21 (0.26) 0.47 (0.26) 0.01 (0.01) 247 (270) 91 (17) 9 (7) 49 (13) 3.4 (1.0) 1.06 0.33 (0.06) 0.12

DePeters et al. 2000 [8] dry 23.6 18.3 5.3 13.3 25.7 51.4 11.9

wet (0.65) (0.9) (0.9) (2.3) (2.3) (1.2) (1.0)

71.2 (2.9) 0.78 (0.03) 0.82 (0.04) 0.53 (0.04) 9.6 (0.3) 16.2 (1.3) 8.7 (1.9) 4.50 (0.25) 0.23 (0.03) 0.63 (0.02) 0.25 (0.01) 0.36 (0.04) 0.02 (0.00) 123.4 (16.5) 93.9 (23.4) 17.4 (2.1) 48.7 (8.8) 2.2 (0.5) 0.24 (0.01) 0.011 (0.03)

27.0 24.3 2.7 11.1 18.0 37.3 10.6

(2.2) (2.0) (0.7) (1.9) (1.9) (3.4) (2.6)

75.9 (1.3) 0.82 (02) 0.87 (0.02) 0.58 (0.02) 6.3 (0.4) 27.9 (5.1) 5.8 (1.1) 4.28 (0.34) 0.24 (0.03) 0.65 (0.06) 0.27 (0.02) 0.26 (0.05) 0.05 (0.02) 138.4 (17.6) 88.4 (8.9) 10.6 (3.1) 49.4 (3.7) 2.9 (0.2) 0.31 (0.03) 0.06 (0.03)

Standard deviation (SD) appears in parentheses. Abbreviations: DM, dry matter; CP, crude protein; Avail. CP, available crude protein; Unavail. CP, unavailable crude protein; Sol. CP, soluble crude protein; ADF, acid detergent fiber; NDF, neutral detergent fiber; TDN, total digestible nutrients; NEL, net energy for lactation; NEM, net energy for maintenance; NEG, net energy for gain; NSC, nonstructural carbohydrates; Ca, calcium; P, phosphorous; Mg, magnesium; K, potassium; Na, sodium; Fe, iron; Zn, zinc; Cu, copper; Mn, manganese; Mo, molybdenum; Se, selenium; S, sulfur; Cl) Ion, chloride. a CP present in the ADF residue. b CP present in the NDF residue.

some nonstructural carbohydrate (NSC) is still present (11% of grain DM) and fat content is higher (>5% of grain DM) than many of the foundation grains used in brewing. Thus, brewers grains have feed value as a source of protein, energy, and fiber in diets of ruminant and nonruminant animals.

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Table 5 A comparison of wet and dry brewers grains amino acid analysis taken from two recent reviews NRC, 2001 [10] Nutrient DM CP Amino Acids Arg His Ile Leu Lys Met Cys Phe Thr Trp Val TEAA

Units % % % % % % % % % % % % % %

of of of of of of of of of of of of

CP CP CP CP CP CP CP CP CP CP CP CP

DePeters et al. 2000 [8]

Dry

Wet

Dry

Wet

90.7 (3.5) 29.2 (4.0)

21.8 (5.0) 28.4 (4.0)

23.6 (0.65)

27.0 (2.2)

5.77 2.00 3.85 7.85 4.08 1.70 1.85 4.60 3.58 0.98 4.75 39.16

4.47 2.25 3.85 9.61 3.40 1.93 1.96 5.57 3.61 0.98 5.14 40.81

4.87 2.19 4.15 7.99 2.55 2.05 2.10 5.90 3.57 1.25 5.81

6.04 2.25 4.32 8.18 4.00 2.18 2.18 5.75 3.82 1.22 5.75

(0.52) (0.20) (0.56) (0.90) (0.32) (0.51) (0.35) (0.43) (0.55) (0.04) (0.59)

(0.95) (0.32) (0.53) (1.13) (0.45) (0.38) (0.51) (0.86) (0.46) (0.17) (0.86)

Standard deviation (SD) appears in parentheses. Abbreviations: DM, dry matter; CP, crude protein; Arg, arginine; His, histidine; Ile, isoleucine; Leu, leucine; Lys, lysine; Met, methionine; Cys, cystine; Phe, phenylalanine; Thr, threonine; Trp, tryptophan; Val, valine; TEAA, total essential amino acids.

The CP content of brewers grains is approximately twice as high as foundation grains because of the removal of most soluble carbohydrate fractions and the relative proportions of carbohydrate initially present in foundation grains. The average CP content of brewers grains ranges from 21% to 29% CP/DM (Tables 3–7), with the variation existing in all sources of grains (eg, different regions of the United States, among wet and dry grains, commercial and microbrewery grains). Earlier reports [2,3,9] listed brewers grains containing as 23% to 25% CP/DM. Many recent data (Tables 3, 4, and 6) list brewers grains as containing 29% to 33% CP/DM. This increase in CP content could be due to improved varieties of barley, corn, and rice being used as foundation grains, different brewing methods, or changes in the recovery or pooling of wastes generated during the brewing process (Fig. 1). Although a good source of CP, the protein in brewers grains is of lesser quality compared with other protein supplements, eg, soybean meal, fishmeal, and essential amino acid profiles of body tissue, milk, and ruminal microbes (Table 5, National Research Council [10]). Its CP value may be greater in ruminant diets because of its value as a bypass source of protein [11]. Holden and Zimmerman [12] reported that lysine and threonine were the first and second limiting amino acids, respectively, for swine fed dried brewers grains. A portion of the CP in brewers grains is soluble (Tables 3 and 6) and present in the A nitrogen fraction [10,13] and thus may be

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Table 6 Wet brewers grains analysis taken from four different breweries Nutrient

Units

Brewery 1

Brewery 2

Brewery 3

Brewery 4

DM CP Deg. CP Sol. CP ADF NDF TDN NEL NEM NEG NSC Fat Ash Ca P Mg K Na Fe Zn Cu Mn Se S

% % % of CP % of CP % % % mcal/lb mcal/lb mcal/lb % % % % % % % % ppm ppm ppm ppm ppm %

22.0 28.0 14.0 2.7 23.0 50.0 72.0 0.73 – – – 6.5 4.5 0.48 0.71 0.23 0.09 0.03 173 134 38 51 0.76 0.24

21.0 32.0 24.0 6.0 22.0 50.0 76.0 0.80 0.85 0.55 – 8.0 4.5 0.31 0.57 0.18 0.09 0.03 301 98 15 57 0.76 0.43

29.0 32.0 24.0 6.0 22.0 50.0 76.0 0.80 0.85 0.55 – 8.0 4.5 0.31 0.57 0.18 0.09 0.03 301 98 15 57 0.76 0.43

26.2 24.2 – – 23.8 46.9 73 0.79 0.79 0.51 18.4 – – – – – – – – – – – – –

Abbreviations: DM, dry matter; CP, crude protein; Deg. CP, degradable crude protein; Sol. CP, soluble crude protein; ADF, acid detergent fiber; NDF, neutral detergent fiber; TDN, total digestible nutrients; NEL, net energy for lactation; NEM, net energy for maintenance; NEG, net energy for gain; NSC, non-structural carbohydrates; Ca, calcium; P, phosphorous; Mg, magnesium; K, potassium; Na, sodium; Fe, iron; Zn, zinc; Cu, copper; Mn, manganese; Se, selenium; S, sulfur. Data provided courtesy of Bill Cromie, Commodity Specialists, Co., Sarasota, FL.

converted into microbial protein, a higher quality protein source. Significant amounts of brewers grains protein are present as B and C nitrogen fractions [9,13] and may escape rumen fermentation. The combination of rumen degradable and bypass protein in brewers grains would have higher nutritive value in ruminant diets than in nonruminant diets. The energy content of brewers grains also varied with source and type of grain: total digestible nutrients (TDN), 71% to 76%; net energy for lactation (NEL), 0.73 to 0.82 mcal/lb; net energy for maintenance (NEM), 0.79 to 0.88 mcal/lb; net energy for gain (NEG) 0.51 to 0.58 mcal/lb (Tables 3, 4, and 6). The fat content of brewers grains range from 5.2% in the NRC (2001) data (Table 4) to 10.1% (Table 3). The dairy cattle NRC [10] incorporates a number of equations for determining energy values. For example, acid detergent fiber (ADF), NDF, crude protein present in the ADF residue (ADF-CP), and crude protein present in

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Table 7 Wet brewers grain analysis from microbreweries located in central New Jersey Microbreweries N 3

DM CP

ADF NDF Hemi Ash Ca

142 % 24.8 20.9 22.3

46.1

23.8

P

Mg

K

Na

3.97 0.22 0.70 0.26 0.07 0.02

Abbreviations: DM, dry matter; CP, crude protein; ADF, acid detergent fiber; NDF, neutral detergent fiber; Hemi, hemicellulose; Ca, calcium; P, phosphorous; Mg, magnesium; K, potassium; Na, sodium. From Altizio BA, Wohlt JE, Schoknecht PA. Nutrient content of spent microbrewery grains and variation with pub and brew type. J Anim Sci 2000;78(Suppl 1):223; with permission.

the NDF residue (NDF-CP) are all used in formulas for calculating NSC, TDN, net energy (NE), and digestible crude protein. The values for ADF, NDF, ADF-CP, and NDF-CP are variable in the grain analyses in Tables 3 and 4. For example, the NDF-CP in Table 3 ranges from 5.41% to 12.89%. This underscores the need to implement a sampling and nutrient analyses program when using any source of brewers grains. The variation can be observed by examining the mean and variation for various nutrients (see Tables 3–7). Means from populations with a large sample size are better estimates of the whole population, unless they have a large variance. Table 6 presents nutrient values for wet brewers grains advertised at individual breweries. Breweries 1, 2, and 3 are owned by the same company. Crude protein varies from 24.2% to 32.0% at the four locations. The ADF and NDF are similar in breweries 1, 2, and 3. Although spent grains produced by microbreweries may vary in several aspects compared with the grains produced at larger breweries, the brewing process is generally as described and illustrated in Fig. 1. Table 7 lists mean values taken at several microbreweries in central New Jersey [14]. The values for all nutrients except CP are similar to those in Tables 3 through 6. According to Altizio et al [14] this difference in CP values is probably due to a more incomplete carbohydrate extraction during malting and mashing phases. This would dilute the protein in the final product. Also, spent microorganisms may be added to the brewers grains at larger breweries. This would be a source of protein not added back in at microbreweries. Brewers grains are a unique feed that can be a pivotal ingredient in ration formulation. Brewers grains contain intermediate amounts of CP and TDN when corn (10% CP/DM) is compared to soybean meal (50% CP/DM) and forages (60% TDN) are compared to corn (90% TDN). Fiber content of brewers grain is comparable to many forages having acceptable quality (50% NDF). In contrast to many forages, brewers grains contain minimal amounts of Ca, Na, and K. Because of their unique nutrient profile, brewers grains can be used as a pivotal feed ingredient in combination with traditional cereal grains, forages, and protein supplements to formulate diets fed for maintenance, lactation, and growth.

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Use of brewers grains in nonruminant diets Pigs Henry and Morrison [2,3] described the use of brewers grains in swine diets. Although wet brewers grains have been used in the diets of finishing swine [2], concerns about transport, storage, and spoilage have limited their use. According to Holden and Zimmerman [12], dried brewers grains can make up a substantial portion of gestation diets, but should not be used as a component of starter diets and should be used only as a minor ingredient in lactation or grower/finisher diets. Table 8 gives some suggested dietary inclusion rates for various by-products. Because of their bulkiness (13% to 16% crude fiber) and low-energy content brewers grains should be limited in the diets of lactating or growing swine. They can, however, be used at higher levels in gestation diets. According to Young and Ingram [15] growing/finishing pigs were fed up to 23% brewers dried grains without a significant reduction in gain or a decline in carcass quality. As the level of dried brewers grains in the diet increased, so did the fiber level. The reduction in performance (ADG) occurred when the fiber level in the diet dry matter increased to more than 6%. The rate of feed conversion was less efficient in pigs receiving the brewers dried grains. These authors also concluded that dried brewers grains could supply up to 50% of supplemental protein needs without a decrease in performance. Walhstrom and Libal [16] successfully used up to 40% brewers dried grains in the diet of gestating sows. Gestation weight gains of 39.5, 47.6, and 32.7 kg were significantly different for sows fed 0%, 20%, and 40% brewers dried grains, respectively. There were no treatment differences in reproductive performance. Litter size and weight of individual piglets, litter weight at birth, and weaning were not affected by treatment. Table 8 Suggested maximum inclusion rates of grain byproducts in swine diets [12] % Grain by-products

Gestation

Lactation

Starter

Grower/Finisher

Dried brewers grains Corn gluten feed Corn gluten meal Corn hominy feed Corn DDGS Rice bran (unextracted) Wheat bran Wheat middlings Wheat shorts

40 90 5 80 40 30 30 30 30

5 5 5 80 5 5 10 10 10

0 0 5 10 5 5 0 5 5

5 5 2 60 20 20 5 20 20

Abbreviation: DDGS, distillers dried grains with solubles. From Holden PJ, Zimmerman DR. Fat in swine nutrition. In: Miller ER, Ullrey DE, Lewis AJ, editors. Swine nutrition. Burlington (MA): Butterworth-Heinemann; 1991. p. 585–93; with permission.

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According to the Pork Industry Handbook [17], constipation in gestating or prefarrowing sows can be prevented by changing to a bulky (more fibrous) diet. Dried brewers grains can be substituted for high-energy feeds such as corn or for other by-products such as wheat middlings in these diets. In spite of their relatively high CP content (28%–30%), dried brewers grain have the same limitations as barley grain [12] when fed to pigs; lysine and threonine being the first and second limiting amino acids for growth. Ileal apparent digestibilities for lysine, threonine, and tryptophan of 68%, 67%, and 71%, respectively, have been reported [18,19]. When used in swine diets, brewers dried grains should be balanced with other feedstuffs that will offset their poor protein quality. Kornegay [20] found that as the level of dried brewers grains increased in the basal diet the digestible energy (DE), metabolizable energy (ME), and digestible crude protein (DigCP) all decreased. Reductions in DE and ME were related to the substitution of dried brewers grains into the higher energy basal diet. Kornegay suggested that the reductions in DigCP in dried brewers grains was related to increasing fiber level. Although net protein utilization (NPU) was also reduced, there was no change in biological value (BV). DE and ME values of 2.65 and 2.38 mcal/kg, respectively, were determined for dried brewers grains. Calvert [21] listed several advantages for using fibrous by-products, such as dried brewers grains, in swine diets. They may provide a source of energy to the pig as a result of fermentation in the cecum and large intestine. They can act as diluents or bulking agents in sow diets, and some by-product feeds can provide a protein source in the diet. In addition, a feed manufacturer or individual swine producer may use various by-product sources to reduce feed costs. One recent study compared wet brewers grains collected from a microbrewery with a corn and soybean meal diet fed to finishing swine [22]. Finishing swine were fed either spent microbrewery grains (see Table 7) or soybean hulls as replacements for corn and soybean meal. Wet spent grains constituted 25% of the diet DM. Although these diets varied in DM content, they were formulated to be isonitrogenous (16% CP on a dry matter basis). A soybean hull control was added to account for the increased fiber in the spent grain treatment. The soy hull and spent grains diets contained similar ADF (7.3%, DM basis), higher than the corn and soybean meal diet (3.3%, DM basis). Energy content of the three diets ranged from 3.1 to 3.3 mcal/kg. Feed intake and conversion efficiency were similar among the three diets. Pigs that were fed the corn and soybean meal, soybean hull, and wet brewers grain treatments gained 0.920, 0.943, and 0.833 kg/day (P  0.07), respectively, and produced carcasses of similar quality. Fiber and moisture content did not affect dry matter intake or average daily gain when the performance of hogs fed wet brewers grains or soybean hulls were compared to a corn and soybean meal control. This was the only study in which wet brewers grains were fed to market hogs.

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Poultry Brewery by-products have very limited value in the diets of poultry. According to Ademosun [23], growing chickens should not be fed brewers dried grains in excess of 30% of diet dry matter. Utilization of dried brewers grains in chickens is limited by their high fiber content. Onwudike et al [24] found that the inclusion of sand in the diet improved the digestibility of brewers dried grains. Sand or grit can aid in the digestion of coarse or fibrous diets. In this study, diet dry matter higher than approximately 15% to 20% dried brewers grains resulted in reduced feed conversion efficiency. Potter [25] found that when fed to growing male turkey poults the protein in brewers grains and brewers grains with yeast was about twothirds digested, but that the gross energy was less than one-third digested. Stengel [1] indicated that another by-product of the brewing process, brewers condensed solubles, can make a good ingredient in poultry or turkey feeds because of their high energy content. Horses Dried brewers grains can make an excellent component of horse diets because they are high in fiber and protein and can provide an excellent substitute for feed grains and protein. In Florida research [4], horses were fed up to 40% brewers dried grains (substituted for oats and soybean meal) in a digestion trial. There were no differences in digestibility of dry matter, crude protein, energy, cell-wall constituents, or soluble carbohydrates. Subsequent studies with foals and yearlings indicated that 20% of brewers dried grains could be fed provided the diet was pelleted and lysine was added. Brewers grains have a lower lysine percentage than soybean meal, and are, in general, a lower quality protein source. It is likely that the amino acidsupplemented brewers dried grains resulted in improved weight gains due to lysine additions. Dried brewers grains are a good feed for horses and can provide a good source of bulk in the diet [4]. They are best used in pelleted or complete diets. They can provide 10% to 20% of dry matter intake for young, growing horses and from 20% to 40% of dry matter intake for older horses. Attention should be paid to the lysine if more than 20% brewers grains are used in the diet. There has been little research completed on feeding wet brewers grains to horses [4]; to avoid spoilage, wet brewers grains could be used when the horses are located close to breweries. Other species Fibrous by-products such as brewers grains may be useful in limiting the energy intake of adult dogs. Any species that can utilize or has a requirement for fiber could be a potential market for brewers grains. The CP

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content of brewers grains averages nearly 30%. In spite of this high level, brewers grains offer a poorer protein quality that may require supplemental protein or amino acids. This is more critical in grower diets than in diets of adult or maintenance animals.

Use of brewers grains in ruminant diets Wet and dry brewers grains are frequently included in diets fed to lactating dairy cattle [26] and have also been fed to finishing beef cattle [27]. This use is justified nutritionally (eg, source of protein, fiber, and energy) and economically (low cost); however, only limited amounts of brewers grains can be fed successfully in the diets of ruminants without dry matter intake and performance being decreased. Long-term storage and spoilage are also major concerns when wet brewers grains are fed. Researchers [28] and producers [26] have utilized brewers grains as a protein supplement in dairy rations. Brewers grains have effectively replaced soybean meal [29–33] and corn gluten meal [33] as protein supplements in dairy rations. Wet and dried forms of brewers grains are effective protein supplements, although the utilization of protein varies with type [28,34]. Due to greater amounts of soluble/ruminal degradable protein, concentrations of NH3-N and numbers of bacteria and ciliated protozoa in the rumen were higher in steers fed wet versus dried brewers grains [34]; however, ruminal digested dry matter was less for wet grains than dried grains possibly due to a greater rate of passage from the rumen by wet grains. Wet and dried brewers grains have greater fractions of rumen escape protein compared to soybean meal [31]. Santos et al [28], in their review of the effects of rumen-undegradable protein on dairy cow performance, pointed out that brewers grains can substitute for soybean meal but will not result in increased performance. When the Cornell Net Carbohydrate and Protein System was used to evaluate absorbable limiting amino acids for milk yield [35], methonine or lysine was limiting when soybean meal was the protein source and lysine was limiting when brewers grains was the source of protein. Although brewers grains can be a source of protein, limitations still exist in amino acid nutrition, requiring additional supplementation or selection of feed ingredients during ration formulation. Brewers grains are also high in structural fiber (see Tables 3 and 4) and have been utilized to provide diet fiber for dairy cows [36,37]. In vitro studies [38] of digestion rates of NDF were similar for brewers grains and alfalfa hay; total tract retention was longer and rates of NDF and ADF disappearance were lower for cattle fed brewers grains compared with alfalfa hay [37]. Dry matter intake was less when brewers grains replaced forage and concentrate for cattle [37] or only alfalfa hay when fed to sheep [39]. Younker et al [37] concluded that brewers grains may be a short-term forage substitute.

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Because of high fiber and fat contents (Tables 3 and 4), brewers grains can be a significant source of energy. In studies of lactating dairy cattle, Murdock et al [40] calculated TDN and NEL to be 78% and 1.76 mcal/kg respectively, for wet brewers grains. Preston et al [27] replaced 0%, 25%, and 50% of the corn with dried brewers grains in the diets of growing and finishing beef steers. The calculated NEM and NEG for dried brewers grains were 2.01 and 1.20 mcal/kg DM compared with 2.55 and 1.5 mcal/kg DM for corn. The growth rate of steers was improved by substituting brewers grains for corn and the elimination of rumen keratosis and liver abscesses in cattle fed brewers grains. In several studies [29,32,40] lactating dairy cows were fed diets in which wet brewers grains contributed 30% of the ration dry matter and feed intake and performance were unaffected. Davis et al [41] reported decreases in dry matter intake and milk production when cows were fed wet pressed brewers grains as 30% of the ration dry matter. Even greater decreases in feed intake and production occurred when wet grains constituted 40% of ration dry matter. Total water intake and water consumed in the feed were significantly lower for cows fed the ration containing 40% pressed grains. To optimize water and dry matter intake, maintain diet digestibility, and allow for ration formulation adjustments, current recommendations [42] suggest that dried and wet brewers grains should constitute no more than 8% and 22%, respectively, of total ration dry matter for lactating cows. The brewing industry currently produces significantly more wet than dry grains. Producers must have proper storage facilities and feeding practices to ensure that grains are fed rapidly, minimizing spoilage. During hot weather, untreated grains can deteriorate within several days. Ensiling with bacterial inoculants or propionic acid [43] or the addition of NH3 [44] have helped to maintain quality during longer-term storage. Another approach to maintaining diet consistency and quality (New Jersey Dairy Farmer Fritz Wainright III, personal communication, 2001) is to feed wet brewers grains only during cooler months. During hotter months, dried brewers grains, reconstituted with water to the same moisture level of wet grains, can be utilized.

Wet brewers grains: quality and spoilage concerns The chief concern about the use of wet brewers grains relates to spoilage. If not used quickly, wet brewers grains will spoil. This results in a less palatable product that may cause health concerns. When feeding wet brewers grains it is important to use them quickly; costs will rise rapidly if spoilage occurs. Small dairies or feedlots may find it difficult to keep feeding rates ahead of spoilage; this will be especially difficult during hot spells. The moisture content will change as moisture drains away and palatability will also decrease. As a total mixed ration component, wet brewers grains can greatly reduce bunk life, especially during the summer.

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Keeping wet brewers grains sealed with plastic may help to prevent aerobic spoilage. If not covered, feeding them from the top down may maintain a relatively anaerobic environment and help in avoiding spoilage. Ensiling may also be a possibility for the storage of wet brewers grains. This requires the ability to cover and seal the pile in order to maintain anaerobic fermentation. An uncovered pile of wet brewers grains will probably have a storage life of less than 5 to 7 days. Farms must have enough cattle present to feed this amount before another shipment arrives. Microbreweries may store spent grains in small containers, and the farmers who use them as feed probably have smaller numbers of animals located nearby. Because the volume of material is smaller, and the material may be kept in airtight containers, spoilage concerns will not be as great; however, if a microbrewery only disposes of spent grains on a weekly basis and does not handle them properly, farmers may be collecting spoiled material. Because microbreweries do not brew on a daily basis, it is important for the farmers to coordinate their collection schedule with the brewing schedule. Another concern associated with the feeding of brewers grains is the possibility of mycotoxin contamination, which can have profound effects upon animal health. Table 9 shows the mycotoxin concentrations found in a small number of samples analyzed at the DairyOne Forage Laboratory in Ithaca, NY. The Council for Agriculture Science and Technology [45] gives a thorough review of the risks of mycotoxins in animal nutrition. The values in Table 9 are well within safety limits described in the CAST [45] report. According to P. Schwarz (North Dakota State University, personal communication, 2001), the primary factors determining whether mycotoxins will be found on the spent grains is the amount present in the malted barley or corn adjunct, as well as the water solubility and heat stability of the toxin. If the toxin is more water soluble, much of the toxin will be transferred to the beer, and less will remain on the spent grains. The boiling process associated with brewing will destroy toxins that are not heat stable. Barley might present problems with tricothecene toxins such as T-2, but DON (vomitoxin) and zearalenone would be the primary problems. Corn might have some of the Table 9 Mycotoxins present in brewers grain samples analyzed by the DairyOne Forage Laboratory in Ithaca, NY (2000–2001) Mycotoxin

Unit

N

Mean

Range

SD

Aflatoxin Vomitoxin Zearalenone T2a Fumonisin

ppb ppm ppm ppm ppm

12 8 7 3 3

5.08 0.33 0.48 0.05 0.07

1.80–8.37 0.08–0.58 0.14–0.83 0.05 0.07

3.29 0.25 0.34 0 0

a T2, trichothecenes. Data provided courtesy of Paul Sirois, DairyOne Forage Laboratory, Ithaca, NY.

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tricothecene toxins, but the fumonosins are probably of greatest concern. For more information on this subject, see Schwarz et al [46].

Summary Brewers grains, a by-product of beer production, are often used as a livestock feed. Because brewers grains provide protein, fiber, and energy, they can be useful in a variety of diets. Protein in brewers grains can meet a significant portion of supplemental protein requirements; in addition, they provide fiber and needed bulk in the diets of ruminants and horses. Brewers grains and other brewers by-products have also been fed to pigs, sheep, and poultry. Currently, the primary market for wet brewers grains is as a dairy cattle feed; however, some may be fed to beef cattle in feedlots. Brewers grains have historically been marketed wet or dry, but wet brewers grains currently make up the majority of the marketed product. Brewers grains provide protein, energy, and fiber in livestock diets, but product variability can influence their utilization and necessitate a testing program to determine nutrient content.

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