Peanut by-products fed to cattle

Peanut by-products fed to cattle

Vet Clin Food Anim 18 (2002) 295–315 Peanut by-products fed to cattle Gary M. Hill, MS, PhD University of Georgia, Animal and Dairy Science Departmen...

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Vet Clin Food Anim 18 (2002) 295–315

Peanut by-products fed to cattle Gary M. Hill, MS, PhD University of Georgia, Animal and Dairy Science Department, Tifton Campus, Moore Highway, P.O. Box 748, Tifton, GA 31793-0748, USA

Peanut (Arachis hypogaea L.) production is well adapted to the temperate climate and sandy soils of the Southeastern United States, extending into Central Texas, Eastern New Mexico, and Eastern Oklahoma. High-quality peanuts are consumed domestically as salted shelled nuts, and in a myriad of processed foods and candies. Currently, there is a growing demand for large Virginia-type peanuts marketed as ‘‘beer nuts’’ in pubs and bars in the British Isles. Peanuts have been grown for more than a century in the Southeastern United States, providing a valuable cash crop for farmers. Before World War II, peanuts were grown for hay and nut production on many farms in the southeast. Of the 336,000 ha of peanuts grown in Georgia in 1939, 83,000 ha (24.7%) were grown for hogging-off (consumption by swine in the fields) [1], and hay was recovered from 75% of the peanut acreage after nut harvest and fed to cattle. Although peanut harvest has become mechanized in the United States and other countries, and the swine industry has changed drastically with vertical integration of hog operations, probably less than 3% of acreage is grown for swine production, although residue hay production is still significant in the Southeastern United States. In 2000, U.S. peanut production was 3.25 billion lb harvested from 1.336 million acres, with average yield of 2444 lb/acre and an estimated value of $835 million (Georgia Agricultural Statistics Service, Athens, GA). Georgia produced 38% of the peanuts harvested in the United States in 2000, at 1.328 billion pounds, the net worth of the crop in Georgia was $2 billion (Georgia Commodity Comm. for Peanuts, Tifton, GA). Peanut production was higher in 2001 than in 2000, with 3.44 billion lb of actual farmer stock, and 4.26 billion lb in commercial storage [2], because of timely rainfall during 2001. In 2002, major changes to the Peanut Quota System are being initiated, and future peanut prices paid to producers are expected to decline sharply over the next 5 years. Price depressions along with expected increased importation

E-mail address: [email protected] (G.M. Hill). 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 9 - 1

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of peanuts through existing trade agreements suggest that peanut acreage in the United States will decline. Obviously, if peanut production declines sharply, peanut by-product output will also decline. With production statistics in mind, the peanut industry furnishes a substantial volume of by-products from processing, including broken and cull peanuts, peanut hulls, and peanut skins (testa). Residual peanut vine hay produced after nut harvest is another substantial by-product. The peanut production region in the United States has a tremendous number of beef cow-calf herds, allowing efficient and economical utilization of peanut byproducts within the area in which they are produced. Topics discussed in this paper will include brief descriptions of major peanut products and by-products, their nutritional value to cattle, antiquality factors, and utilization of by-products in production diets for cattle. Peanuts and peanut meal Raw peanuts are quite nutritious, containing relatively high concentrations of protein and energy derived from the high oil content of the nuts, but whole peanuts are not generally fed to cattle. In 2001, raw peanuts in the shell before drying, that were marketed through the national peanut quota system in the United States, were sold for $630/ton. Occasionally, raw peanuts and peanut meal are available from processors because of some abnormality, usually higher aflatoxin content than allowed for human consumption. These peanuts can be utilized as supplemental feeds for cattle on a limited basis, but producers should obtain a valid, accurate analysis of aflatoxin content to prevent possible aflatoxin poisoning of cattle. State departments of agriculture and veterinary diagnostic laboratories are sources of information regarding testing for aflatoxin in grains, peanuts, and other agricultural products. Several reports of toxic effects of aflatoxin contained in peanut meal and peanuts have been listed [3], mostly occurring in foreign countries. Because of the value of domestically produced peanuts, probably less than 1.0% of the annual production is fed as raw peanuts to cattle in a given year. Peanut meal is available from peanut processing plants throughout the peanut producing areas, but it is usually not priced competitively with cottonseed meal or soybean meal. The ash, crude protein (CP) and total digestible nutrients [(TDN) dry matter (DM) Basis, %] of peanut meal (6.3, 52.3, and 77.0, respectively), comparable to 41% solvent-extracted cottonseed meal (7.0, 45.6, 76.0, respectively), and (6.5, 55.1, 87.0, respectively) for solvent extracted soybean meal [4]. Peanut meal is approximately 5% lower in CP and 13% lower in TDN than soybean meal, but it has similar TDN and slightly higher CP than cottonseed meal [4]. Comparisons of peanut meal with soybean meal revealed higher concentrations of niacin, pantothenic acid, riboflavin, and thiamin in peanut meal, but lower concentrations of the essential amino acids lysine, methionine, and tryptophan in peanut meal

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than soybean meal [5]. For growing pigs, peanut meal was substituted for 30% to 50% of soybean meal in standard diets without affecting performance [6]. Later research indicated that lysine added to corn–peanut meal diets could meet growing pig protein requirements [7]. Although peanut yields were vastly improved by the late 1970s with available peanut cultivars compared to those planted in the previous decade, protein quality was not improved in peanut meal with newer cultivars as measured by performance of growing swine [8]. Concentrations (as-fed, %) of lysine, methionine, and threonine, the three amino acids considered most limiting for growing cattle, were 1.77, 0.42, and 1.16, respectively, for peanut meal, compared with 2.90, 0.65, and 1.70, respectively, for soybean meal [9]. Because ruminants are less dependent on dietary amino acids than nonruminants to meet protein requirements, peanut meal could be utilized as a supplement for growing cattle and cow herds, if it is available at prices competitive with soybean meal and cottonseed meal. Peanut skins Peanut skins (testa) can be used in livestock feeds, and they are a readily available feed source in the peanut-producing areas that also have peanut processing, such as blanching plants. Often peanut blanching plants are constructed within or adjacent to peanut crushing and peanut butter plants. Shelled peanuts are blanched through mechanical processes, and the peanut skins are removed and dried. In some locations, individuals with means of transporting semitruck and trailer loads of peanut skins, contract for the entire production from one or several plants within a location. These larger contractors then market the peanut skins to livestock feed producers and other uses. Peanut skins have been used successfully to suppress odors in swine waste pits [10], and in laying hen houses [11]. Peanut skin production in the United States varies with crop production and utilization of peanuts, and estimated annual production is between 20,000 and 30,000 metric tons. Peanut skins constitute a relatively small percentage of the peanut pod and kernel weight, resulting in lower volume available for animal feeding. Peanut skins are the most intriguing peanut by-product, because they have relatively high concentrations of fat (ether extract) and CP, but they are relatively low in fiber (Table 1). The mean chemical composition of peanut skins derived from four research articles displayed in Table 1 compares favorably with the concentrations listed in a national feed ingredient publication [7], with similar ash, CP, and crude fiber, but higher ether extract in the national publication [7]. The differences in ether extract might have resulted from different blanching processes, which has caused differences ranging as high as 25% to 30% in ether extract concentrations from plant to plant, even within the same area (G.M. Hill, unpublished data). All peanut skins used in studies at the Coastal Plain Station, Tifton, GA, were obtained from the same plant, thereby adding consistency to the diets being

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Table 1 Chemical composition of peanut skins and ammonia treated peanut skins Ammonia treated peanut skinsc

Peanut skins Item Chemical composition Dry matter Ash Ether extract Crude fiber Crude protein Nitrogen-free extract Neutral detergent fiber Acid detergent fiber Acid detergent lignin Tannin

Meana

SE

Feedstuffs (2001)b

92.6 2.5 21.4 14.3 17.6 44.2 33.8

0.35 0.07 0.58 0.55 0.13 0.27 2.49

94.0 3.0 25.5 12.6 17.4 — —

23.9 5.6 21.0

1.15 0.56 0.95

16.0 — —

Study 1d

Study 2e

% of Dry matter 88.2 90.3 2.7 2.5 22.9 21.0 15.9 13.6 25.3 26.5 33.2 36.6 43.2 39.0 28.2 8.6 11.8

31.6 14.1 11.9

Mean

SE

89.2 2.6 22.0 14.8 25.9 34.9 41.1

1.05 0.10 0.95 1.15 0.60 1.70 2.10

29.9 11.4 11.8

1.70 2.75 0.05

a Simple mean of peanut skin analyses reported by McBrayer et al (1983) [15], Hill et al (1986a, 1986b) [22,23] and Hill et al (1987) [24]. b Data from Feedstuffs. Feedstuffs reference issue & buyers guide. Vol. 73(29). Carol Stream (IL): Feedstuffs; 2001. c Peanut skins packed in large plastic bags; peanut skins treated with 3% anhydrous ammonia by weight. d Data from Hill GM, Utley PR, Newton GL. Influence of dietary crude protein on peanut skin digestibility and utilization by feedlot steers. J Anim Sci 1986;62:887–94. e Data from Hill GM, Utley PR, Newton GL. Digestibility and utilization of ammoniatreated and urea-supplemented peanut skin diets fed to cattle. J Anim Sci 1986;63:705–14.

formulated and to resulting animal responses. Peanut skins are not listed in most feed ingredient tables, including some listings of by-product feedstuffs, presumably because of relatively low volume produced, and lower utilization in livestock diets. Few by-product feeds compare with peanut skins for CP and ether extract content (17.5%, and 21% to 25%, respectively; Table 1). Peanut skins were listed at 65% TDN in a national publication [4], which was similar to dried brewers grain (66%), higher than soybean hulls (53%), and lower in TDN than cottonseed meal (75%) and dried citrus pulp (77%) in the same publication. Although protein and energy content of peanut skins are high, making them attractive as a least-cost analysis feed ingredient for growing-finishing beef cattle and lactating dairy cattle, practically no ingredient table indicates the high tannin content of peanut skins, as shown in Table 1. Additional studies reported similar high concentrations of CP, ether extract, and tannins in peanut skins [12–14], comparable to values in Table 1. Although grain producers in the midwest were concerned with high tannin content (2% to 4%) in bird-resistant sorghum grains in the 1970s and 1980s, experiments were being conducted with peanut skins containing 16% to 23% tannin in dry matter, which had a potential impact on swine and cattle performance. Sorghum, with lower tannin content, was being fed at higher proportions of the diet than peanut skins.

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In initial research with peanut skins added to finishing beef cattle diets [15], tannin content was not suspected to be a detrimental factor to finishing cattle performance, even though growing-finishing swine performance was depressed on 10% and 20% peanut skin diets [12]. Feeding peanut skins at levels up to 10% of the diet did not affect feedlot steer performance, but feedlot heifer average daily gain (ADG) was depressed significantly at 10%, and even further when diets contained 20% peanut skins (Table 2) [15]. Interestingly, feed intake remained fairly high for heifers fed 0%, 10%, or 20% peanut skins (7.84, 7.76, and 6.52 kg DM daily), but feed/gain increased markedly with increasing dietary peanut skins (5.8, 11.4, and 55.6). Observing digestibility and N balance data for steers fed the three levels of peanut skins (Table 2) reveals that increasing level of peanut skins resulted in large depressions in DM and CP digestion, and similar depressions in N retained, especially for the 20% peanut skin diet. Fecal N increased for each increase in dietary peanut skins (Table 2), resulting in fecal N proportion on the 20% peanut skin treatment that was almost twice the level of the controls. Urinary N was lower for diets with peanut skins, but increased fecal N was the greatest cause of depressed N balance. Interestingly, ether extract digestibility was unchanged by peanut skin additions [15], but DM and CP digestibility were reduced (Table 2). Tannins contained in the diets ranged from 0.4% to 3.9% (Table 2), and were thought to be the reason for depressed performance. Clearly, increased fecal N resulting from binding of N by tannins in peanut skins in these finishing diets resulted in protein deficiency. Many problems associated with feeding various feedstuffs containing high tannin concentrations to various species of animals have been reviewed [16–18]. Tannins and other phenolic compounds form polymers with dietary protein that are nutritionally unavailable, and tannins bind with enzymes [19]. Urea has been effective in reversing tannin inhibition of enzymes [20], and urea effectively reduced tannic acid inhibition of rumen proteolysis [21]. Various methods of reducing effects of tannins on performance have been documented [18], including increasing dietary CP concentration. Considering these factors, along with the results of a study in which ADG was improved by 19% in growing heifers grazing rye pasture that were fed a supplement containing equal portions of cracked corn and peanut skins compared with feeding cracked corn [15], the idea of increasing dietary CP to overcome detrimental effects of tannins in peanut skins seemed plausible. In preliminary research, finishing steers had similar performance on cornbased diets with peanut skins added at levels up to 9.1% of the diet [15], and ADG was improved in steers fed Tifton 44 bermudagrass pellets containing 10% peanut skins compared with control steers fed pellets with no peanut skins [13]. If peanut skins could be included at levels higher than 10% of the diet without affecting performance, this would allow increased utilization of this relatively cheap by-product that supplies both energy and CP in the diet. Because 20% peanut skins in the diet of finishing steers caused depressed performance [15], experiments were conducted to compare 15% peanut skins

Corn/SBM Corn/PS Corn/PS Corn/3.8% SBM Corn/PSd Corn/AM.PSe Corn/13.5% SBM, Also 15% Peanut Skins Corn/7% SBM, 1% Urea Corn/SBM Corn/0.6 % urea Corn/AM.PS Corn/0.7 % ureaf Corn/0.3 % urea Corn/0.7 % urea Corn/1.1% urea

Grain/protein

13.2 12.7 12.4 12.4 12.0 13.0 14.0

16.0

15.0

— 15.0 15.5 — 15.0 15.0 15.0

11.8 12.5 12.4 11.4 11.4 12.2 15.5

CP, % of DM

— 10 20 — 15.0 16.0 15.0

PS, %

1.1 4.1 3.2 1.2 5.5 5.8 5.5



0.4 2.2 3.9 — — — —

Tannin, %

— — — 91 91 91 91

40

40 40 — 40

No. d

98 98 98 — 140 140 140

1.68a — — — 1.80a 0.87c 1.09b 1.17b

109

1.69a 0.40b — 1.80a

Overall, d 100 100 100 109 — — 109

ADG, kg

Performance

70.6a 79.0a 62.5b 59.0b 72.2a 58.0b 60.6b 60.2b

1.38a 1.04b 1.35a — 0.90 1.05 1.08

78.0a 70.5b 61.6b 76.4a 58.7b 55.2b 71.4a

1.38a 0.70b 0.14c 1.47 — — 1.43

1.39

DM

ADG, kg

72.4a 44.4b 37.9b 67.9a 42.4c 47.1b 50.6b

55.4b

60.6a 43.9b 30.7c 64.0a 34.1c 33.4c 55.7b

CP

23.7b 46.2a 50.8a 26.7b 49.2a 50.3a 49.4a

46.7bc

27.9c 41.6b 54.7a 26.8 51.0ab 53.2a 44.7c

Fecal N

27.5a 9.2b 7.2b 24.8a 18.3bc 15.8c 23.3ab

24.1a

20.2a 15.9a 8.0b 22.1a 5.6b 9.1b 22.9a

N retained

N balance, %

Metabolism steers Digestibility, %

Abbreviations: CP ¼ crude protein; DM ¼ dry matter; PS ¼ peanut skins; ADG ¼ average daily gain; SBM ¼ soybean meal; AM.PS ¼ ammoniated peanut skins. abc Within each experiment, means in columns bearing different superscript letters differ (P\0.05). d Steers removed from treatment after 40 days poor performance. e This treatment only used in metabolism experiment. f Steers removed after 91 days, finished, and slaughtered.

Hill et al. (1986b) [23] (n ¼ 54, steers) Hill et al. (1987) [24] (n ¼ 46, steers)

McBrayer et al. (1983) [15] (n ¼ 18, heifers) Hill et al. (1986a) [22] (n ¼ 96, steers)

Reference

Diets

Table 2 Finishing steer gains and metabolism steer apparent digestion and N balance when fed corn-based diets with peanut skins

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in finishing diets with crude protein levels near finishing steer requirements and at higher levels (Table 2) [22]. The higher CP diets contained either 13.5% soybean meal or 7% soybean meal with 1% urea. Because tannins in peanut skins bind with N, causing protein deficiencies, feeding a high level of urea was feasible. At the same time, peanut skins were treated with 3% anhydrous ammonia by weight in a large plastic bag, and fed in the metabolism trial (Table 2). Ammonia treatment increased peanut skin CP to 25.3% while slightly increasing ether extract and neutral detergent fiber (NDF) and acid detergent fiber (ADF) compared with untreated peanut skins (Study 1; Table 1). The most important result of ammoniation was the 44% reduction of peanut skin tannin content to 11.8% (Study 1; Table 1). Feeding 15% peanut skins on the 11.4% CP diet resulted in a 40-day ADG of 0.4 kg, compared with 1.69 kg for controls (Table 2) [22], forcing the removal of these steers fed peanut skins. These steers showed classic signs of protein deficiency, including long, rough hair coat, and lethargy. Interestingly, steers fed control and low-CP peanut skin diets consumed similar amounts of feed (10.8 versus 10.6 kg/day), resulting in feed:gain of 27.2 for the peanut skin diet. During the first 40 days and for the 109-day trial, steers on the two high-CP diets had ADG similar to controls, indicating that elevating the CP level allowed increased peanut skin feeding and no performance depressions. Metabolism steers fed the five diets (Table 2) had similar DM digestibility for control and high CP diets, but lower DM digestibility for the low-CP peanut skin diet and ammoniated peanut skin diets compared with the other treatments. Digestibility of CP was highest for the control diet, intermediate for high CP peanut skin diets, and lowest for low-CP peanut skin and ammoniated peanut skin diets. Fecal N was lowest for controls and higher for all peanut skin diets, indicating that tannins were binding N, even on the high-CP diets. Similar N retention was observed for control and high-CP peanut skin diets, which was higher than diets with low-CP and ammoniated peanut skins. Although increased CP diets with 15% peanut skins, using natural protein or a mixture of urea and soybean meal, were effective in overcoming performance depressions, CP digestibility was lower and fecal N was higher than controls. The N retained was similar for control and high-CP peanut skin diets. When feedlot data were compared [15,22], the breaking point for severe performance depression in feedlot cattle fed corn–soybean meal diets containing 11% to 12% CP appears to be between 10% and 15% peanut skins in diets (Table 2). Effects of low-level urea supplementation of 15% peanut skin diets and ammoniation of peanut skins were studied as practical methods of meeting dietary protein requirements and reducing detrimental effects of peanut skin tannin on performance of beef cattle (Table 2) [23]. Ammoniation of peanut skins increased CP to 25.9%, and reduced tannin content to 11.9% (Study 2; Table 1). Pretreatment of peanut skins with 3% ammonia allowed tannins to bind with available N before the peanut skins were fed to cattle, thereby reducing binding of dietary N. Feeding urea as a supplemental N source

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allowed tannins to bind with some of the excess N available as urea was broken down in the rumen of cattle. Tannin content of the ammoniated peanut skin diet was lower than in the urea–peanut skin diet (Table 2) [23], and steer ADG was similar for control and ammoniated peanut skin diets, and significantly lower for the urea–peanut skin diet. Steers on the urea–peanut skin diet did not have enough finish to be slaughtered, and they remained on the diet to day 147, compared with 98-day finishing for control and ammoniated peanut skin diets. Metabolism steers had lower DM and CP digestibility, higher fecal N, and lower N retention when fed diets containing peanut skins compared with control steers. Plasma urea nitrogen was similar in metabolism steers fed control and urea–peanut skin diets, and both were higher than in steers fed ammoniated peanut skins [23]. Even though N balance was lower for steers fed ammoniated peanut skins than control steers, feedlot performance of steers was comparable with controls, indicating that this was an effective treatment in overcoming effects of tannins in peanut skins. Although steers on the low-urea peanut skin diet had lower ADG than controls (Table 2) [23], performance was vastly improved for these steers relative to previous studies [15,22] (Table 2), when 15% or 20% peanut skins were fed with soybean meal supplemented diets. Because feeding urea is safer and a more practical method of increasing dietary N than ammoniation, and because feedlot performance was improved in low-CP and high-CP diets containing urea with 15% peanut skins (Table 2) [15,22], a feedlot experiment was conducted with dietary urea from 0.3% to 1.1% with 15% peanut skins [24]. Tannin content of these diets was above 5% in peanut skin diets. Control steers had the highest ADG, followed by steers fed 0.7% and 1.1% urea with peanut skins, and finally steers fed 0.3% urea with peanut skins at 91 days. Control steers were removed from the experiment and slaughtered, but urea–peanut skin steers remained on the three diets through 140 days (Table 2) [24]. Metabolism steers were fed the four diets and control steers had higher DM digestibility and lower fecal N than peanut skin treatments. Retained N was similar for control and 1.1% urea–peanut skin diets, which were higher than 0.3% and 0.7% urea–peanut skin diets. Increasing dietary crude protein from 12% to 14% with urea in 15% peanut skin diets was not effective in overcoming tannin effects on steer performance. Urea supplementation, even at low levels, did improve performance on the peanut skin diets compared with previous research using soybean meal supplemented finishing diets (Table 2). Even at 1.1% dietary urea, which is above the recommended limit for cattle diets, apparently there was insufficient N provided to prevent tannins from binding dietary N and reducing steer performance. In another steer feeding experiment [25], peanut skins replaced soybean hulls at 0.0%, 7.5%, or 15% of 10.5% and 15.5% CP diets. Steer ADG decreased linearly with increasing level of peanut skins in the l0.5% CP diets, and ADG increased linearly with increasing peanut skin level in 15.5% CP diets. Steers fed 15% peanut skins on the low-CP diet had an ADG of

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0.34 kg, compared with 1.42 and 1.35 kg for 0.0% and 7.5% peanut skin diets. These results agree with earlier research when low-CP and high-CP peanut skin diets were fed to finishing cattle [15,22,23]. Peanut skins can be fed with other by-product feeds and silages if dietary N is high enough to overcome detrimental effects of peanut skin tannins. This point is illustrated by research in which lactating dairy cattle were fed peanut skins in a total mixed ration containing concentrates, alfalfa, and corn silages at 0.0% to 24% in dietary DM [14]. Diets contained more than 17% CP, and tannin content ranged from 3.93% to 7.92% for peanut skin diets. Milk yield was increased for increasing levels of dietary peanut skins compared with controls, and milk fat percentage increased up to 16% peanut skins. Productive performance of dairy cows was not as severely affected as in beef cattle diets containing peanut skins, and peanut skins can be included up to 16% of the diet to improve performance if dietary CP is above 16% CP. Peanut skins can be effectively utilized in beef cattle diets that are high in dietary CP, or in supplements when cattle are grazing high-CP forages such as rye, ryegrass, or wheat, without affecting performance. Diets must be formulated to provide high levels of dietary N, usually exceeding animal requirements, to avoid protein deficiencies that can cause severe depressions in performance and death of animals. Natural protein sources should be fed to meet requirements of cattle, with urea or ammoniated peanut skins added to increase available N in the diets if 15% peanut skins are being fed to avoid performance depressions. For growing cattle grazing high-CP forages, improved gains may occur if peanut skins and corn are fed in equal portions at about 2.0 kg/animal daily. If forage matures or is diminished by freeze in winter or drought in summer, feeding regimen should be changed immediately, because the system depends on an adequate, continuous supply of high-CP forage to bind with peanut skin tannins. Peanut hulls In the United States, most peanut pods are mechanically removed from inverted roots using special combines, and the pods are transported to central processing points, dried, and stored. Later, they are transported to shellers for further processing, including mechanical separation of shells or hulls from nuts. Peanut hulls constitute approximately 20% of the dried pod and nut weight, resulting in a tremendous tonnage of this residue annually. In 2001, farmer stock equivalent peanut production was 1.56 million metric tons [2] (3.44 billion lb), resulting in 312,000 metric tons of peanut hulls produced in the United States. Available peanut hull production varies annually with peanut crop production. In the past, most peanut hulls were disposed of by burning at or near the shelling plants. Over the years, peanut hulls have found many uses, including roughage in cattle diets and in commercial feeds, fuel to run boilers for manufacturing processes, mulch for horticultural plants, bedding in broiler houses, soil conditioners, specialty

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uses including kitty litter, pelleted products, and carriers for other chemicals and fertilizers. If tested and found to have very low aflatoxin content, peanut hulls can be effectively utilized as bedding in dairy cattle loafing barns. Peanut hulls are fragmented in the shelling process, and they usually contain nut kernel fragments and shriveled nuts, which increases nutritive value compared with the pure hull [26]. Nutrients in peanut hulls differ from cottonseed hulls, with ash, CP, crude fiber, and TDN (% of DM), respectively, for peanut hulls at 4.2, 7.8, 62.9, 22; and 2.8, 4.1, 47.8, 42 for cottonseed hulls [27]. Compared with cottonseed hulls, peanut hulls are more fibrous, contain more fines, and do not stimulate intake in the same manner as cottonseed hulls. Peanut hulls are lower in digestibility than other by-products and grasses, with in vitro dry matter disappearance (IVDMD) of 24.2% for peanut hulls compared with 69.6% for soybean hulls, 59% for 8-week maturity Coastal bermudagass, and 54.6% for tall fescue [28]. In a series of trials to determine quality, digestibility, and utilization of peanut hulls in cattle finishing diets, different levels of whole peanut hulls were added to steer finishing diets [29]. They included 10%, 20%, or 30% peanut hulls in corn-based diets compared with an all-concentrate diet. Steer ADG was similar for each hull level, and significantly higher than the allconcentrate diet. Adjusted ADG indicated a quadratic effect for hull levels from 0% to 30% of the diet, with an indication that levels of 10% and 20% were more desirable than 0% or 30% peanut hulls for promoting weight gains in steers. Feed intake increased proportionally with the level of hulls in the diet, resulting in similar concentrate intake for all treatments. Apparent digestion of the diets indicated higher DM and crude fiber digestibility for the all-concentrate diet. Peanut hulls were later included in a comparison of roughage sources using 288 finishing cattle [30]. Corn-based diets were fed that contained one of the six roughage sourcs: (1) 92% ground snapped corn with husks (supplying both energy and roughage), (2) 20% Coastal bermudagrass pellets, (3) 20% cottonseed hulls, (4) 20% coarsely ground peanut hulls, (5) 8% Coastal bermudagrass pellets, and (6) 2% oyster shells or 27% corn field residue. Steer and heifer feedlot performance and carcass characteristics were unaffected by roughage source. These studies indicate that peanut hulls can be included at 10% to 20% of the diet without affecting feedlot performance while providing adequate fiber for normal ruminal function. To improve digestibility of peanut hulls, studies were conducted with various chemical treatments applied to the peanut hulls. Chemicals used in these processes include sodium chlorite, ammonia, sodium hydroxide, chlorine gas, and calcium hypochlorite, and several other more exotic chemicals. Some of these chemicals are quite corrosive, and may be dangerous to use. Peanut hulls of different cultivars from several locations were subjected to several chemical treatments, including sodium hydroxide, ammonia, and chlorine gas, but sodium hypochlorite was the only treatment that improved IVDMD (treated ¼ 40% versus untreated ¼ 25%) of the peanut hulls [24].

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Sodium hydroxide treatment of peanut hulls that were included at 20% of concentrate diets fed to rams depressed crude protein digestibility, but did not affect digestion of other dietary components [31]. Alkali treatment or extrusion cooking of peanut hulls did not affect digestion of organic matter, ADF or NDF, however, alkali treatment increased hemicellulose digestibility [32]. Anhydrous ammonia was injected into large sealed plastic bags containing coarsely ground peanut hulls at 3% by weight [33], and peanut hull dry matter decreased and crude protein in dry matter increased (untreated hulls ¼ 90.5% DM, 8.3% CP versus treated ¼ 88.5%, 17.5%). Corn-based 11.4% CP diets were formulated that contained 0.6% urea and 20% untreated peanut hulls, or 20% ammonia treated peanut hulls, and fed to metabolism steers and feedlot heifers. Similar organic matter and crude protein digestibility occurred for the two treatments, but NDF digestibility was reduced for the ammoniated peanut hull treatment. Nitrogen retention was higher for steers, plasma urea nitrogen was lower for heifers fed the ammoniated peanut hull diet, and 112-day feedlot performance was similar for heifers fed the two diets. These studies underscore the resistance of peanut hulls to chemical treatments used to improve digestibility. The low digestibility might result from the inherent properties of the cellulose fraction [28], because they found that digestibility of true cellulose isolated from peanut hulls was very low compared with other roughage sources. Peanut hulls were fed locally to beef cattle as farmer-feeders through the 1970s, and many local shellers would either provide unground or coarsely ground (passed through a screen with 1.9-cm diameter holes) hulls to farmers and larger feedlots. Some producers ran whole peanut hulls through hammer mills with the screens removed to break very large hulls, but keep particle size fairly large to increase the roughage factor for the cattle. As the feeding industry became more concentrated, many shellers became reluctant to coarsely grind hulls for local use. Finely ground hulls and pelleted hulls could be handled through auger systems and transported at less cost. Major feed companies often incorporate ground or pelleted peanut hulls in cattle feed formulations as a fiber and roughage source that is generally more economical than cottonseed hulls. They often use other roughage sources, and are not concerned with finely ground hulls that constitute a small percentage of the diet formulations. Despite repeated warnings to feed manufacturers and farmerfeeders to use coarsely ground peanut hulls in high-concentrate diets, most peanut hulls fed to cattle during the last two decades have been finely ground. Ground peanut hulls and pelleted peanut hulls cause markedly increased incidence of liver abscesses, and have detrimental effects on rumen papillae and villae, which are needed for effective ruminal digestion of feeds. Allconcentrate and 10%, 20%, and 30% peanut hull diets were fed to finishing steers [29], and the all-concentrate and 10% peanut hull treatments each had liver abscesses occurring in 44% of the steers at slaughter compared with none in the 20% and 30% peanut hull treatments. Considering these results [26], studies were designed to compare effects of physical form of peanut

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hulls included at 20% of diets fed to 81 steers for 135 days. Peanut hulls were fed unground in the form they arrived from the sheller, finely ground through a screen with 0.32-cm holes, or ground through the 0.32-cm screen and pelleted. Steers fed unground peanut hulls tended to have higher ADG, and similar feed:gain compared with ground or pelleted hull treatments. Digestibility of DM, CP, and crude fiber were unaffected by treatments. Carcass traits were similar for the treatments, with a trend for lower carcass weights on ground and pelleted treatments. Two of 27 steers on the ground peanut hull treatment suffered from anorexia and severe weight loss after 3 months of feeding, and were removed from the experiment, and their performance data was excluded. Postmortem examination of these steers showed extreme rumen hyperkeratosis, black pigmentation, and clumping of villi in the rumen and severe abscesses in the liver. When the remaining steers were slaughtered, liver abscesses were detected in steers fed unground, finely ground, and pelleted peanut hulls at these respective percentages (number of steers with abscesses/number of steers per treatment): 3.7 (1/ 27); 56 (14/25); 59 (16/27). Therefore, the physical form of peanut hulls may affect metabolic processes in finishing cattle, and finely ground and pelleted peanut hulls substantially increase liver abscesses. In a study designed to evaluate effects of high-level vitamin E supplementation of feedlot cattle on incidence of liver abscesses and color stability of beef steaks [34], corn-based finishing diets with 20% pelleted peanut hulls were fed to 60 steers to enhance potential for incidence of liver abscesses, based on previous research with pelleted hulls [26]. Steer ADG averaged 1.49 kg, and feed:gain averaged 7.00, across vitamin E treatments during the 133-day trial. Liver abscesses at slaughter tended to be lower for steers fed vitamin E than for control steers (21.4% versus 41.4%). Although vitamin E supplementation tended to reduce liver abscess incidence, physical form of peanut hulls caused a substantial increase in the incidence of these abscesses. More attention should be paid to the physical form of peanut hulls included in cattle diet formulations. Producers often feed large quantities of peanut hulls, some allowing cattle free-choice access to the hulls, to all classes of cattle without regard to physical form because they perceive the hulls as being a relatively cheap and available feed source. Performance and health data of cattle affected by improper feeding of peanut hulls is not available, and problems are probably diminishing in number with fewer farmer-feeders in the southeast, increased utilization of peanut hulls in industry, and by large commercial feed companies. Although digestibility of peanut hulls was not improved by ammonia treatment, crude protein was doubled by adding 3% ammonia, and the resulting stable ammoniated peanut hull product could be efficiently used as both a protein supplement and a roughage source in a variety of ruminant diets. If properly processed, and fed at correct levels in diets, peanut hulls can be effectively utilized in a variety of diets for all classes of beef cattle.

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Peanut hay, perennial peanuts, and peanut silage Peanut hay Peanut hay is produced throughout the peanut belt, and is fed as a winter feed supplement to growing stocker cattle, beef replacement heifers, and wintering cow herds. Estimates indicate that postharvest hay was produced on 25% to 40% of the total peanut acreage in 2001. Vegetative peanut vines have been grazed by cattle on a limited basis, and perennial peanut has been grazed and harvested for hay in Florida and along the Gulf Coast. Farmers have traditionally harvested tremendous volumes of residual peanut vine hay across the belt. Before improved peanut combines and harvesting equipment began to appear in the 1960s, most of the peanuts were dug and vines with peanuts attached were stacked and dried or moved into windrows before threshing or combining. Almost all residual peanut vines produced were fed to cattle as hay on family farms. Peanut hay has continued to be an important feedstuff for wintering beef herds across the region. Many producers rely on peanut hay, especially in drought years when it often becomes the primary hay source, or as a planned proportion of the annual hay fed to beef cows. This hay source is available during autumn, when dry conditions usually prevail across the Southeastern United States, allowing good hay harvesting conditions, and large volumes of hay can be baled within a few weeks, rather than over an entire spring–summer season as with grass hay. Production costs are substantially lower for residual peanut hay compared with grass hays, especially for producers who own the peanuts being harvested for hay for their own cow herds. Modern peanut-harvesting equipment results in green peanut vines being plowed from the soil, inverted mechanically to expose roots and nuts to the sun for drying. After several days of drying, special combines are then used to harvest the peanuts in pods from the roots and stems. This process has become very efficient in harvesting raw peanuts, but the process ensures that tremendous amounts of soil are displaced, with much of it adhering to peanut vines and leaves, which elevates ash content of the hay. Nevertheless, beef cattle will readily consume large portions of medium- to high-quality peanut hay. Occasional cases of ruminal compaction have occurred when beef cows consume too much peanut hay in a short period of time. Different combines result in differences in hay and stem length, quality, and quantity of peanut vine material remaining for hay. Leaves on peanut plants are highly nutritious, like alfalfa and other leguminous crops; however, leaf shatter is often significant through mechanical harvesting of nuts. Perhaps the most critical factor affecting hay quality is timing of combining following initial peanut plowing and inverting. If harvest is delayed by prolonged rainfall, if inverted peanuts are not harvested within a few days, and if vine moisture is too high, hay quality will suffer greatly. Untimely rains after inversion may prolong harvest schedules, lowering hay quality. Most producers

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are primarily interested in nut harvest and yield of their valuable cash crop, with secondary consideration of hay quality. Many peanut producers forgo hay production and incorporate the deteriorated vines as organic matter. This is especially true in larger operations that do not own or feed cattle of their own. Significant damage occurs to hay quality, and molds may form if hay is harvested after heavy rains or if vines are not dried sufficiently. Peanut hay is porous, and it requires storage in barns or sheds, plastic wrapping of bales, or immediate feeding. Autumn and winter rains may penetrate large round bales of peanut hay to the center, or all the way through, if stored unprotected outside. Some of the peanut hay produced is utilized as mulch in horticultural enterprises. There is an inherent liability in feeding peanut hay to livestock, because many of the chemicals used in peanut production are not labeled for use in livestock production. To date, cases of toxicity and residues from these chemicals in meat animals fed peanut hays have not been reported or identified, although some residues have been found in milk samples. Aflatoxin concentrations are occasionally at high enough levels in peanut hay to cause problems for cattle. In a study from Australia [35], acute aflatoxicosis caused the death of 12 of 90 drought-stricken Hereford calves fed peanut hay with a concentrate. In a case study from Georgia [3], feeder steers were fed 60% ground corn, 39% ground peanut hay, and 1% mineral mixture, and the corn fed in the ration was found to be contaminated with high levels of aflatoxin. In this study, 14 of 30 steers died of acute aflatoxicosis. More recently, an outbreak of acute respiratory distress syndrome affecting herds fed peanut vine hay in southeastern Virginia [36]. Among the herds investigated, 125 adult cattle fed peanut hay died. Although incidence rates of acute respiratory distress syndrome are small relative to the volume of peanut hay fed and huge number of herds, these reports indicate the devastating results that can occur if conditions are favorable for an outbreak. Peanut hay was fed in these case studies, but in general, mycofoxicosis is not a major problem when feeding good quality, nonmoldy peanut hay to cattle. Nutritional value of peanut hay is quite high for cattle if the hay is properly harvested and stored to prevent rain damage [37,38,39]. Although peanut hay has been fed for more than 75 years in the United States, very few research reports have been published concerning peanut hay utilization by beef or dairy cattle. In an early study [39], whole-plant late-season peanuts harvested green with nuts attached were dried for 2 to 6 weeks, then threshed to remove nuts, and residual hay was baled, resulting in minimal leaf shatter and retention of green color. That hay contained 10% CP, 20.9% crude fiber, and 8.6% ash. Total feed intake, hay intake, and milk production were very similar for dairy cows fed peanut hay or good-quality alfalfa hay. In another study [38], diets composted of concentrates plus coarsely ground alfalfa hay, unground peanut hay, and ground peanut hay were fed to dairy cows, resulting in similar milk production for the different hays. They reported similar TDN for alfalfa and peanut hays (53% versus

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54%), and higher digestible CP for alfalfa than peanut hays (10% versus 7%). The CP in the concentrate, alfalfa hay, and peanut hay, respectively, were 16%, 14%, and 11%. They reported hay refusals of 5% for alfalfa hay, and 22% and 21%, respectively, for long and ground peanut hay. Peanut vine residue hay produced after peanuts were inverted, sun dried, and nuts harvested with a conventional combine was fed to growing beef heifers and metabolism steers [38]. Chemical composition of peanut hay and bermudagrass hay is shown in Table 3. Ash content of peanut hay is high because of the dirt and sand attached during the harvesting process and the fibrous composition of the plant material. The CP was similar for both sources of peanut hay analyses (Table 3), and TDN was reported at 55% in two ingredient analysis tables [4,28]. Comparing peanut hay with Tifton 44 bermudagrass hay [38], crude protein and crude fiber were similar, but peanut hay had lower NDF and higher ADF than bermudagrass hay (Table 3). In the feeding experiment, growing heifers had higher ADG on Tifton 44 hay than on peanut hay. After adjusting hays to an organic matter basis, apparent digestibility of DM, CP, and nitrogen free extract were higher for peanut hay than Tifton 44 bermudagrass hay, but crude fiber and NDF digestion were higher for Tifton 44 hay than for peanut hay. Perennial peanut Perennial peanut (Arachis glabrata) hay differs from the residue peanut hay produced following nut harvest in autumn. Perennial peanut is often referred to as ‘‘rhizoma’’ peanut, because it produces few seeds, and it is usually vegetatively propagated from rhizomes [40]. Although perennial peanut forage for grazing and hay are not technically by-product feeds, they are important related feeds to residue peanut hay, and are produced in the southern part of the peanut belt. Perennial peanut has been established on sandy soils, primarily in north Florida, southern Georgia, and southern Alabama. It is sensitive to frosts, so it is usually planted well to the south of a line running from Albany and Tifton, GA, to Dothan, AL. It can tolerate temperatures as low as 15 degrees F, but protracted cool periods greatly reduce forage production potential [40]. It is persistent, once established, covering the ground and enduring prolonged droughts. It is comparatively slow in establishing stands, often taking 2 or more years to cover fields. It can be grazed in rotation or harvested for hay, usually yielding two to three cuttings annually, and autumn harvests are discouraged because of required nutrient storage in plant rhizomes for persistence through winter [40] . Quality of this hay is similar to alfalfa hay if it is properly harvested without leaf shatter [41]. Many producers market the hay at prices equal to or above excellent quality alfalfa hay, and much of the hay is marketed in square bales for horses. All classes of cattle can be fed these hays, but highly productive cows, primiparous cows, and growing calves receive feeding priority to efficiently utilize the higher quality hay.

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Table 3 Chemical composition of peanut hay and bermudagrass hay Source 1a c

Tifton 44 Composition DM Ash Crude protein Ether extract Crude fiber Nitrogen-free extract Neutral detergent fiber Acid detergent fiber Acid detergent lignin TDN

— — 11.0 2.4 34.4 52.2 78.5 41.8 5.4 —

Source 2b Peanut hay

% Organic DM — — 10.2 2.2 35.4 52.2 56.9 49.9 9.4 —

Peanut hay % DM 91.0 8.6 10.8 3.4 33.2 — — 41.0 — 55.0

a

Data from McBrayer AC, Utley PR, McCormick WC. Comparison of high quality peanut hay and Tifton 44 bermudagrass hay when fed to yearling heifers. Research Report 383. Athens (GA): University of Georgia College of Agriculture Experimental Station; 1981. b Data from Feedstuffs. Feedstuffs reference issue & buyers guide. Vol. 73(29). Carol Stream (IL): Feedstuffs; 2001. c Tifton 44 bermudagrass hay.

Perennial peanut hay (2.27 kg/cow daily) was compared with a commercial protein supplement fed to wintering beef cows and heifers with basal diets of bahiagrass hay and molasses, resulting in similar cow pregnancy rates and calf adjusted weaning weights for the two sources of supplement [42]. The 2-year mean in vitro organic matter disappearance (IVOMD) and CP in DM (%), respectively, for perennial peanut hay and bahiagrass hay were: 58.7 and 12.2, 36.2 and 5.9. These studies suggest that perennial peanut hay could be used as a protein supplement for wintering cows on low protein hays. In a 20-week study with growing goats [43], those fed perennial peanut hay (17.1% CP, 45.8% NDF) had higher average daily gain (P\0.10) and improved feed/gain (P\0.10) compared with goats fed alfalfa hay (18.0% CP, 45.3% NDF). In a metabolism trial with goats fed the hays, higher organic matter, crude protein, and fiber fraction digestion occurred on the perennial peanut hay treatments. Nitrogen retained was similar for the two treatments, but retained N as a parentage of N intake was higher for alfalfa hay than perennial peanut hay. The high quality of perennial peanut forage invited investigation of growing-finishing cattle performance to take advantage of the locally grown forage in a region that has difficulty in growing alfalfa and other legumes because of acidic sandy soils, dry environment, and often poor drainage of rainfall. Growing stocker steers were grazed on bahiagrass or a mixture of bahiagrass, common bermudagrass, and perennial peanut pastures from April to September [44]. The bahiagrass and the grass portions of the mixed treatment

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had similar CP and IVOMD, each of which declined over the season (18.6–6.3% CP, 67.4–45.2% IVOMD). These values were higher compared with the grasses throughout the season (28.6–13.9% CP, 78.0–63.6% IVOMD). Although there was an interaction of years with treatments resulting from increased perennial peanut in the sward (Year 1 ¼ 26%; year 2 ¼ 45%), steers grazing perennial peanut-mixed grass had higher ADG than steers grazing bahiagrass pastures (ADG, 2-year means, 0.79 versus 0.51 kg). In a forage finishing study [45], ADG was lower for steers grazing perennial peanut during both growing and finishing phases (0.49 and 0.94 kg), compared with steers fed concentrates in these phases (0.78 versus 1.33 kg). Forage finished steers had lower carcass weights, smaller ribeye area, less fat over the ribeye, less steak tenderness because of higher shear force values, and slightly lower carcass quality grades than concentrate-finished steers. Cowcalf herds grazing bahiagrass pastures during summer [46] were assigned to pastures with or without a calf grazing area of perennial peanut during the 98-day study from June until September. Creep grazing perennial peanut resulted in improved ADG (0.91 versus 0.72 kg, P\0.05), higher weaning weights, and trends for increased frame size (hip height). These reports indicate that perennial peanut can boost growing and finishing cattle performance, and improve preweaning calf performance in herds grazing low-quality forages before weaning in autumn. Although annual peanuts potentially could be grown as a grazing crop for cattle, present production costs of peanut may be prohibitive. However, with uncertainty in the Peanut Quota System, and a resurgence of interest in stocker cattle production in the region, research is needed to determine seeding rates, disease and insect problems, and grazing management systems for current peanut cultivars. Forage yields of annual peanuts of 8 Mg/ha have been reported [47], and midseason defoliation of the canopy resulted in depressed pod yield. Effects on nut yield if a hay crop is harvested and timing of the harvest could affect recommendations for obtaining hay from annual peanut crops grown for nuts. Recently, two popular cultivars of annual peanut, ‘‘Southern Runner’’ and ‘‘Georgia Runner’’ were harvested to a 120-mm stubble height at midseason, or at midseason and immediately before inverting in one experiment, and at 60, 70, or 80 days after planting, or full-season unharvested in a second experiment [48]. Midseason defoliation significantly reduced peanut pod yield, and delaying defoliation from 60–80 days after planting further reduced pod yields. Digestibility of foliage samples averaged above 65%; stems and whole plant leaves had similar digestibility. In these experiments, potential returns from hay production would not offset losses incurred through reduced nut yields. Additional research is warranted, with different annual peanut cultivars and defoliation management systems to best alleviate loss of revenue from reduced nut yields following defoliation. If peanut prices fall substantially in the future, economics of the forage/peanut crop enterprise may be altered.

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Peanut silage Nutritional value of whole plant annual peanut as a silage crop is enticing, based on the high-yield potential of the crop and quality of the stems and leaves. When whole-plant annual peanuts were harvested at the proper maturity for pod harvest by uprooting, mechanically shaken to remove soil, chopped, and ensiled, the resulting silage contained 31.5% dry matter, 15.4% CP, 16.5% ether extract, and 57% NDF [49]. In a feeding trial with growing heifers fed corn silage (8.2% CP; 51.3% NDF) or a diet of 50% corn silage, 50% peanut silage, dietary intake was 14% higher for heifers fed the corn– peanut silage diet than those fed corn silage alone. Digestibility of CP and ether extract were higher, and digestibility of NDF and DM were lower for the corn–peanut silage diet compared with the corn silage diet. In the study, treatment of the chopped peanuts with a propionic acid–formaldehyde preservative altered ensiling, fermentation, but treatment failed to affect responses of heifers fed the treated silage diets. In a study using perennial peanut silage fed to lactating dairy cows [50], increasing peanut silage in diets replacing corn silage resulted in quadratic effects on dry matter intake, DM and CP digestibility, and milk yield in Holstein cows. In this study perennial peanut silage proved to be high in quality, because overall dairy cow performance was not affected when perennial peanut silage replaced up to 70% of corn silage in 50% concentrate diets. Additional research is warranted to identify effects of perennial peanut silage and haylage fed to lactating beef and dairy cattle. Additional research should be undertaken to determine feeding value of perennial peanut silage and from annual peanut silage harvested at various times before nut harvest for currently grown cultivars, and to determine effects on subsequent nut yields. These silages could be highly nutritious for beef or dairy herds, especially in emergency feeding situations.

Summary Peanut by-products supply substantial quantities of feedstuffs to beef cattle grown in the same region where peanuts are produced. Included in the list of products fed to cattle are peanuts and peanut meal, peanut skins, peanut hulls, peanut hay, and silages. Residual peanut hay is by far the most widely used peanut by-product fed to beef cattle, and if it is properly harvested with minimal leaf shatter, it is comparable to good-quality grass hays in nutrient content. Peanut skins are often included in small quantities in cattle and pet foods, supplying both protein and energy. High tannin content of peanut skins can cause severe performance depressions in beef cattle if peanut skins are included at levels higher than 10% of the diet, unless diets contain relatively high CP (above 15% CP), or additional N sources are added such as ammonia or urea. Because dairy cattle diets are often above 16% CP in the total dietary DM, peanut skins may increase milk production

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when added at levels up to 16% of the dry matter. Peanut hulls are effectively used as a roughage source at levels up to 20% of beef finishing diets, for bedding in dairy cattle loafing sheds (if tested and found to contain low aflatoxin levels), and in a variety of manufactured products. Peanut hulls are economically priced because of their quantity, their inherent high fiber, and low CP content, and they should not be fed as a primary feedstuffs for beef cattle. Peanut by-products are generally priced below other by-products, and they can be incorporated into a variety of supplements and diets for cow herds, growing-finishing cattle, and dairy cattle.

References [1] Parham SA. Peanut production in the coastal plain of Georgia. Tifton (GA): University of Georgia Coastal Plain Expimental Station Bulletin 34; 1942. [2] NASS. Peanut stocks and processing. Washington, DC: National Agricultural Statistics Service, USDA; 2002. [3] Colvin BM, Harrison LR, Gosser HS, Hall RF. Aflatoxicosis in feeder cattle. J Am Vet Med Assoc 1984;184:956–8. [4] Feedstuffs. Feedstuffs reference issue & buyers guide. Vol. 73(29). Carol Stream (IL): Feedstuffs; 2001. [5] Pond WG, Maner JH. Swine production in temperate and tropical environments. San Francisco (CA): WH Freeman Co.; 1974. [6] Kornegay ET, Meacham TN, Thomas HR. The use of peanut meal in swine rations. Research Division Bulletin 32. Blacksburg (VA): Virginia Polytechnic Institute; 1968. [7] Thomas HR, Kornegay ET. Lysine supplementation of high lysine corn and normal cornpeanut meal diets for growing swine. J Anim Sci 1972;34:587–91. [8] Hale OM, McCormick WC. Performance and carcass traits of pigs on diets containing varying amounts of peanut meal. Peanut Sci. 1979;6:96–8. [9] Dale N. Ingredient analysis table. 2001 edition. In: Feedstuffs reference issue & buyers guide. Vol. 73(29). Carol Stream (IL): Feedstuffs; 2001. [10] Newton GL. Use of peanut skins (testa) as an odor suppressant in swine waste pits [abstr.]. J Anim Sci 1981;53(Suppl. 1):171. [11] Reynnells RD, Newton GL, Sellers S. Peanut skins (testa) for odor reduction in laying hen houses [abstr.]. Poult Sci 1985;64(Suppl. 1):168. [12] Hale OM, McCormick WC. Value of peanut skins (testa) as a feed ingredient for growingfinishing swine. J Anim Sci 1981;53:1006–10. [13] Utley PR, Hellwig RE. Feeding value of peanut skins added to bermudagrass pellets and fed to growing beef steers. J Anim Sci 1985;60:329–33. [14] West JW, Hill GM, Utley PR. Peanut skins as a feed ingredient for lactating dairy cows. J Dairy Sci 1993;76:590–9. [15] McBrayer AC, Utley PR, Lowrey RS, McCormick WC. Evaluation of peanut skins (testa) as a feed ingredient for growing-finishing cattle. J Anim Sci 1983;56:173–83. [16] Kumar R, Singh M. Tannins: their adverse role in ruminant nutrition. J Agric Food Chem 1984b;32:447–53. [17] McLeod MN. Plant tannins—their role in forage quality. Nutr Abstr Rev 1973;44:803. [18] Price ML, Butler LG. Tannins and nutrition. Agrriculatural Experimental Station Bulletin No. 272. Lafayette (IN): Purdue University; 1980. [19] Jung HG, Fahey GC. Nutritional implications of phenolic monomers and lignin: a review. J Anim Sci 1983;57:206–19. [20] Goldtein J, Swain T. The inhibition of enzymes by tannins. Phytochemistry 1965;4:185–92.

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[21] Kumar R, Singh M. Recovery from tannic acid-inhibited proteolysis in the rumen by urea. Indian J Anim Sci 1984a;54:438. [22] Hill GM, Utley PR, Newton GL. Influence of dietary crude protein on peanut skin digestibility and utilization by feedlot steers. J Anim Sci 1986a;62:887–94. [23] Hill GM, Utley PR, Newton GL. Digestibility and utilization of ammonia-treated and urea-supplemented peanut skin diets fed to cattle. J Anim Sci 1986b;63:705–14. [24] Hill GM, Utley PR, Newton GL. Dietary urea influences on digestibility and utilization of diets containing peanut skins by steers. J Anim Sci 1987;64:1–7. [25] Utley PR, Hill GM, West JW. Substitution of peanut skins for soybean hulls in steer finishing diets containing recommended and elevated crude protein levels. J Anim Sci 1993;71:33–7. [26] Utley PR, Lowrey RS, McCormick WC. Peanut hulls as a source of roughage in cattle finishing diets. Tifton (GA): University of Georgia College of Agriculture, Coastal Plain Station, Tifton Research Bulletin 154; 1974. [27] NRC. Nutrient requirements of domestic animals. Nutrient requirements of beef cattle. 6th revised edition. Washington, DC: National Academy of Science, National Research Council; 1984. [28] Barton II FE, Amos HE, Albrecht WJ, Burdick D. Treating peanut hulls to improve digestibility for ruminants. J Anim Sci 1974;38:860–4. [29] Utley PR, McCormick WC. Level of peanut hulls as a roughage source in beef cattle finishing diets. J Anim Sci 1972;34:146–51. [30] Utley PR, Lowrey RS, McCormick WC. Types of roughage and intermittent changes of roughage types in beef cattle finishing diets. J Anim Sci 1973;37:395–8. [31] Maglad ME, Lutfi AAA, Gabir S. The effect of grinding groundnut hulls either with or without alkali treatments on digestibility of diet and on ruminal and blood components. Anim Feed Sci Technol 1986;15:69–77. [32] Chandra S, Prasad DA, Krishna K. Effect of sodium hydroxide treatment and/or extrusion cooking on nutritive value of peanut hulls. Anim Feed Sci Technol 1985;12:187–94. [33] Hill GM, Utley PR. Nutritional value of ammoniated peanut hulls in beef cattle diets. Nutr Rep Int. 1987;36:1363–70. [34] Hill GM, Stuart RL, Utley PR, Reagan JO. Vitamin E effects on finishing steer performance [abstract]. J Anim Sci 1990;68(Suppl. 1):557. [35] McKenzie RA, Blaney BJ, Connele MD, Fitzpatrick LA. Acute aflatoxicosis in calves fed peanut hay. Aust Vet J 1981;57:284–6. [36] Roberson JR, Warnick L, Swecker WS, Whittier WD, Blodgett DJ, Robertson JL. Acute respiratory distress syndrome in adult cattle fed peanut-vine hay. Vet Med 1997;92(7): 644–50. [37] Hawkins GE, Autrey KM. Peanut hay for milking cows. Leaflet No. 53. Auburn (AL): Agricultural Experimental Staation of the Alabama Polytechnic Institute; 1957. [38] McBrayer AC, Utley PR, McCormick WC. Comparison of high quality peanut hay and Tifton 44 bermudagrass hay when fed to yearling heifers. Research Report 383. Athens (GA): University of Georgia College of Agriculture Experimental Station; 1981. [39] Ronning M, Kuhlman AH, Cave HC, Gallup WD. Feeding tests with threshed peanut hay for dairy cattle. Bulletin No. B-400. Stillwater (OK): Oklahoma Agricultural Experimental Station, OK A&M College; 1953. [40] Ball DM, Hoveland CS, Lacefield GD. Southern forages. 2nd edition. Norcross (GA): Potash & Phosphate Institute and Foundation for Agronomic Research; 1996. [41] Prine GM, Dunavin LS, Moore JE, Roush RD. ‘‘Florigraze’’ rhizoma peanut, a perennial forage legume. Gainesville (FL): Florida Agricultural Experimental Station Circular S-275, University of Florida; 1981. [42] Hammond AC, Padgett LJ, Williams MJ. Relative feeding value of Rhizoma perennial peanut hay as a supplement to bahiagrass hay for wintering beef cows and heifers. Prof Anim Sci 1992;8(3):48–54.

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[43] Gelaye S, Amoah EA, Guthrie P. Performance of yearling goats fed alfalfa and Florigraze rhizoma peanut hay. Small Ruminant Res 1990;3:353–61. [44] Williams MJ, Hammond AC, Kunkle WE, Spreen TH. Stocker performance on continuously grazed mixed grass-rhizoma peanut and bahiagrass pastures. J Prod Agric 1991;4:19–24. [45] Bennett LL, Hammond AC, Williams MJ, Kunkle WE, Johnson DD, Preston RL, et al. Performance, carcass yield and carcass quality characteristics of steers finished on rhizoma perennial peanut hay (Arachis glabrata)-tropical grass pasture. J Anim Sci 1995;73:1881–7. [46] Williams MJ, Chase CC Jr, Hammond AC. Interaction of dam breed and creep grazing on growth of Romosinuano calves. Indianapolis, IN: Proceedings of the American Forage and Grassland Council; 1998. p. 88–92. [47] Gorbet DW, Stanley RL Jr., Knauft DA. Forage potential of cultivated peanut (Arachis hypogaea L.). Peanut Sci 1994;21:112–5. [48] Gates RN, Culbreath AK. Forage yield and leaf spot infection response of peanut to defoliation. Peanut Sci 2002;29, in press. [49] Johnson JC Jr, Butler JL, Williams EJ. Composition and nutritive value of whole plant peanuts (Arachis hypogaea L.) ensiled with and without propionic acid-formaldehyde treatment. J Dairy Sci 1979;62:1258–63. [50] Staples CR, Emanuele SM, Prine GM. Intake and nutritive value of Florigraze Rhizoma peanut silage for lactating dairy cows. J Dairy Sci 1997;80:541–9.