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Peanut skins


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Common names 

Peanut skins, peanut bran, groundnut skins, groundnut bran


The fruit (pod, nut) of the peanut (Arachis hypogaea L.) is made of an external shell (or hull) (21-29%) and of the nut itsef (79-71%), which consists of the kernel (69-73%), the germ (2.0-3.5%) and of a enclosing thin hull (testa or seed coat) (2-3%), usually paper-like and coloured, more commonly referred to as the peanut skin (van Doosselaere, 2013; Davis et al., 2016). Peanut skins are a by-product of the blanching process, which consists in removing the skins using peelers, which have rollers covered with abrasive material allowing the skin extraction. Blanching is often done in specialised plants and carried out to prepare peanuts for the manufacture of snack food, peanut butter and other peanut-based foods (Hill, 2002). Marketed peanut skins contain not only the actual skins but also some kernels, kernels fragments and germs (Sobolev et al., 2004). It should be noted that in francophone Africa this product is more accurately called peanut bran (son d'arachide) (CIRAD, 1991).

Like all seed hulls, peanut skins have a high fibre content, but due to the presence of residual kernels and germs they are also very rich in protein and oil, with a large variability due to differences between blanching processes. Both the fibre content and the extremely high tannin content of peanut skins makes them usable only for ruminants (and possibly for rabbits). Also, like all other peanut products, peanut skins may be contaminated with aflatoxins. For those reasons, while peanut skins are used to feed ruminants in peanut-producing areas, their utilisation as feed remains limited with inclusion rates lower than 10% (Constanza et al., 2012). Research is under way to better utilize peanut skins, notably as a source of natural antioxidants for food and feed (Constanza et al., 2012).


Peanut is a major crop widely distributed throughout tropical, subtropical, and warm temperate areas in Asia, Africa, Oceania, North and South America, and Europe (Freeman et al., 1999). Even though crushing peanuts for oil and meal remains a major use for peanut production, direct utilisation for food has been steadily increasing since the 1970s. About 45% of the world peanut production was used for food in 2010-2013, but 60% or above of the production goes to the food market in North America, Southern Africa, West Africa, Southeastern Asia, but that's only the case for 41% of the production in Eastern Asia and 13% in Southwestern Asia (Fletcher et al., 2016). The worldwide production of peanuts (with shells) was 40 million tons in 2015. 40% was produced in China alone, 19% in the other Asian countries, 18% in Africa and 11% in the Americas (USDA, 2016). Assuming that 45% goes to food, it can be estimated that 18 million t of peanuts are produced for the food market. Of these peanuts, a significant proportion undergoes blanching, resulting in the production of peanut skins. In the United States, individuals contract for the entire production from one or several blanching plants and then market the peanut skins to livestock feed producers and other uses. Peanut skin production in the USA varies with crop production and utilization of peanuts, and was estimated to be between 20,000 and 30,000 t in the early 2000s (Hill, 2002).

Nutritional aspects
Nutritional attributes 

Peanut skins are relatively rich in protein (13-21% DM) with a high and very variable content in residual oil (3-27% DM) and fibre (crude fibre 15-45% DM), including lignin (4-27% DM), due to differences in seed maturity, variety and blanching processes. Tannin content can be extremely high, and is often about 20% DM. In the USA, the oil content of peanut skins was found to vary from plant to plant, even within the same area (Hill, 2002). Peanut oil contains about 50% oleic acid and 30% linoleic acid but there are large variations in their respective proportions: reported values for oleic acid range from 35 to 82% and values for linoleic acid range from 3 to 43%, due to natural variations and also to the existence of oleic-rich (and linoleic-poor) varieties (Davis et al., 2016; Pattee, 2005).

Potential constraints 


Peanuts are particularly vulnerable to contamination by fungi Aspergillus flavus and Aspergillus parasiticus. These fungi produce aflatoxins, that are known to cause cancers in humans, increase incidents of hepatitis viruses B and C, lower the immune response, impair growth in children and cause childhood cirrhosis. In poultry and livestock, aflatoxin can cause feed refusal, loss of weight, reduced egg production, and contamination of milk (ICRISAT, 2016). Aflatoxin contamination may occur in the field, after peanuts are dug but before harvest, during transport, and during storage (Payne, 2016). As of 2016, the maximum authorised content in the EU for aflatoxin B1 in feed materials is 0.02 mg/kg (20 ppb or µg/kg) (Commission Directive 2003/100/EC). The risk of aflatoxins in peanut products is discussed more extensively in the Peanut meal datasheet.

Peanut skins, like other parts of the peanut fruit, can be contaminated with aflatoxins, and a study has found that the blanching process, which consists in removing the skins, decreased the amount of aflatoxins by 27%, indicating that a significant amount of the toxin is in the peanut skin (Siwela et al., 2011). However, the risk should be reduced for peanut skins produced in countries where regulatory agencies and the peanut industry enforce strict norms for quality and safety throughout the supply chain, from the harvest to the transportation of peanut end-products (Cowart et al., 2016).


Peanut skins are particularly rich in tannins. Reported values range from 20-25% (Hill et al., 1986a; Hill et al., 1986b) to more than 45% (Sanders, 1979). It is possible that the latter extreme values refer to "pure" skins while the former and lower values refer to the mixture of skins and kernel fragments marketed as peanut skins. Peanut skins tannins are procyanidins, which interfere with protein digestion absorption and hence adversely affect animal performance (Constanza et al., 2012).

Low density

Peanut skins have a very low bulk density that makes them difficult to mix in livestock diets (Palmer, 2010).


Peanut skins can supply both protein and energy to ruminant diets, but their high tannin content is detrimental to cattle performance when they are included above 10% in beef cattle diets and above 16% in dairy diets. It is necessary to raise the protein content of the diets using natural or artificial sources of nitrogen to overcome the binding effects of peanut skins tannins and to prevent protein deficiencies that can cause severe depressions in performance and even death (Hill, 2002). In lambs, peanut skins could be included at up to 20% without adverse effects (Abdelrahim et al., 2012).

Dairy cattle

Peanut skins can be used in diets for lactating cows without impairing milk performance, but should be limited to about 16% of the diet, and diets should exceed the recommended minimum protein content. Higher inclusion rates of peanut skins caused a decline in ruminal ammonia and protein digestibility, probably related to the formation of indigestible tannin-protein complexes (West et al., 1993).

Beef cattle

Several experiments in the USA concluded that peanut skins could be utilized to feed dairy and beef cattle provided that the diet contains enough protein, usually exceeding requirements. Feedlot cattle can be given high protein diets containing up to 10% peanut skins or 15% ammoniated peanut skins, or 15% peanut skins with urea. Grazing cattle can consume high-protein forages such as rye, ryegrass, or wheat supplemented with peanut skins and maize fed in equal portions at about 2 kg/d (Hill, 2002). Feedlot heifers fed 10% peanut skins showed depressed protein digestibility and feedlot performance: the average daily gain with 10% skins was half that of the gain obtained with the control diet. However, feedlot steers fed 9% peanut skins maintained growth. This inconsistency appears to be related to the amount of consumed tannins relative to the amount of consumed protein (McBrayer et al., 1983). Steer calves fed pellets made of Bermuda grass and 10% peanut skins gained 27% faster than control animals with not difference in feed intake and feed efficiency. However, levels higher than 5% decreased pellet durability and reduced the acceptability of the pellet for feeding and mechanical handling (Utley et al., 1985). In feedlot steers, increasing dietary protein level to 16%, in 15% peanut skin diets, using soybean meal or a soybean meal-urea combination, was effective in overcoming the detrimental effects of peanut skin tannins (Hill et al., 1986a). Ammonia treatment of peanut skins prior to feeding may provide a method of increasing their feeding value, while eliminating the need for additional supplemental protein (Hill et al., 1986b). Increasing dietary urea was not effective in overcoming detrimental effects of peanut skin tannins on digestibility and performance of feedlot steers fed diets containing 15% peanut skins (Hill et al., 1987). In finishing steer diets including 15% soybean hulls, peanut skins could be substituted for 50% of the soybean hulls where the diet contained 10.5% protein, and they could completely replace soybean hulls where the diet contained 15.5% protein (Utley et al., 1993).


In Gulf Coast ewe lambs fed peanut skins up to 40% dietary level, peanut skins could replace a portion of maize and soybean meal without any adverse effects on carcass characteristics or lambs performance, though the rib eye area was greater in lambs fed the control diet or 20% peanut skins, than in lambs fed 40% peanut skins (Abdelrahim et al., 2012).


Peanut skins are not a good feed ingredient for pigs due to their high fibre and tannin content. In a study conduced in the USA, peanut skins included at 10% in the diet of growing-finishing pigs depressed feed efficiency and had a negative effect on nutrient digestibility and N metabolism. A diet containing 20% peanut skins was unpalatable, as pigs rooted some feed out of the self-feeders in an attempt to sort out the peanut skins (Hale et al., 1981). Peanut skins have been used successfully to suppress odors in swine waste pits (Newton et al., 1981).


Peanut skins are rich in fibre and tannins and, when considering the risk of aflatoxin contamination, are not a good feed for poultry. In Ghana, peanut skins could be included only at 5% in the diet of broiler chicks with no adverse effect on health and performance (Atahuene et al., 1989). In the USA, peanut skins have been used successfully to suppress odors in laying hen houses (Reynnells et al., 1985).


Information on the use of peanut skins in rabbit feeding in international literature is very scarce. Smallholder rabbit farmers in Ghana use it as a concentrate supplement for rabbits fed green forages (Karikari et al., 2009). In Egypt, peanut skins introduced in a balanced diet for growing rabbits provided acceptable growth and slaughter performance when included at 18% dietary level, in association with peanut hulls (6%) and berseem hay (24%) as sources of fibre. Incorporation at 36% in association with peanut hulls (24%) resulted in a significant alteration of performance (El-Gamal, 2003).

More studies are necessary to determine the precise conditions of utilisation of peanut skins in rabbit feeding. Its chemical composition, and particularly the lipids content, may vary widely in relation with the proportion of residual seeds in the by-product (Waller, 2010). Peanut skins appear to have an energy value ranging from poor (DE 6.9 MJ/kg DM) to rich (DE 14.6 MJ/kg DM), depending on the amount of residual lipids (Lebas, 2016). Peanut skins are rich in lignified fibre, which is beneficial to rabbits. The main issue, however, remains the important risk of aflatoxin contamination, as the skins carry a large part of the aflatoxin load of the peanut kernel (Siwela et al., 2011). As a consequence, given the present scarcity of information concerning the utilisation of peanut skins in rabbit feeding, and given the high risk of aflatoxicosis, this feed cannot be recommended for rabbits until it is more thoroughly studied.

Nutritional tables
Tables of chemical composition and nutritional value 

Avg: average or predicted value; SD: standard deviation; Min: minimum value; Max: maximum value; Nb: number of values (samples) used

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 92.8 1.1 90.8 94.5 16  
Crude protein % DM 16.9 2.6 13.1 21.4 19  
Crude fibre % DM 23.2 12.5 11.6 44.8 15  
NDF % DM 41.4 12.4 25.3 61.5 15  
ADF % DM 33.4 13.1 20.4 56.2 14  
Lignin % DM 13.6 8.7 4.3 27.3 11  
Ether extract % DM 15.9 8.4 3.3 27.3 22  
Ash % DM 5.0 3.2 2.4 11.8 18  
Gross energy MJ/kg DM 21.8 0.7 21.8 23.8 4 *
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 2.0 0.4 1.4 2.5 10  
Phosphorus g/kg DM 1.5 0.3 1.0 2.0 10  
Potassium g/kg DM 11.7 4.2 6.2 17.0 8  
Sodium g/kg DM 1.3   0.1 2.5 2  
Magnesium g/kg DM 1.7 0.3 1.1 2.1 8  
Manganese mg/kg DM 45 11 32 54 3  
Zinc mg/kg DM 38 8 31 47 3  
Copper mg/kg DM 24 19 12 46 3  
Iron mg/kg DM 481   262 699 2  
Amino acids Unit Avg SD Min Max Nb  
Alanine % protein 3.8       1  
Arginine % protein 8.0       1  
Aspartic acid % protein 10.7       1  
Glutamic acid % protein 15.3       1  
Glycine % protein 13.6       1  
Histidine % protein 3.0       1  
Isoleucine % protein 3.2       1  
Leucine % protein 5.9       1  
Lysine % protein 4.6       1  
Methionine % protein 0.4       1  
Phenylalanine % protein 4.3       1  
Proline % protein 4.0       1  
Serine % protein 6.1       1  
Threonine % protein 2.9       1  
Tyrosine % protein 3.6       1  
Valine % protein 4.1       1  
Secondary metabolites Unit Avg SD Min Max Nb  
Tannins (eq. tannic acid) g/kg DM 184.9 41.3 94.0 238.0 8  
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 59.4       1  
Energy digestibility, ruminants % 59.3         *
DE ruminants MJ/kg DM 12.9         *
ME ruminants MJ/kg DM 10.4         *
Nitrogen digestibility, ruminants % 18.5   10.4 26.5 2  

The asterisk * indicates that the average value was obtained by an equation.


Abdelrahim et al., 2012; AFZ, 2011; Atuahene et al., 1989; CIRAD, 1991; Hale et al., 1981; Hill et al., 1986; Hill et al., 1986; Hill et al., 1987; McBrayer et al., 1983; Okai et al., 1984; Saito et al., 2016; Sibbald, 1979; Utley et al., 1985; West et al., 1993

Last updated on 01/10/2016 14:21:31

Datasheet citation 

Heuzé V., Thiollet H., Tran G., Lebas F., 2016. Peanut skins. Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. http://www.feedipedia.org/node/697 Last updated on October 4, 2016, 10:38

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