Dr. Jacquie Jacob Ph.D., University of Kentucky
NOTE: Before using any feed ingredient make sure that the ingredient is listed in your Organic System Plan and approved by your certifier. If you intend to feed barley to organic poultry, the barley must be certified organic.
Barley (Hordeum vulgare) is commonly grown for malting, but can also be grown for food and animal feed. It is the main feed ingredient in some parts of western North America, and in many European countries that are less suitable for growing corn. Barley can also be grown as a pasture crop.
Barley can play an important role in crop rotation in organic production systems. It has an extensive root system that makes it able to compete with weeds; and is often used to break disease, insect, and weed cycles associated with other crops. Direct rotation with other small grains is not recommended when there are alternatives available. The small grains left behind can harbor disease or insect pests (Brown, 2003).
There are several different varieties of barley that can be classified in a number of ways:
Nutrient content of barley (Batal and Dale, 2010)
The available energy content of barley grain can vary widely, largely due to the presence of beta-glucans. Beta-glucans (ß-glucans) are referred to as "anti-nutritional factors" because inclusion of feedstuffs containing ß-glucans depresses nutrient digestion in poultry. The chemical structure of ß-glucans makes it difficult for poultry to digest. The ß-glucans combine with water in the intestine to form a gel that increases the thickness–or viscosity–of the intestinal contents, resulting in reduced nutrient availability. The increased viscosity can also result in increased instances of 'pasty vents' in chickens, especially chicks. Beta-glucan levels in barley are affected by the cultivar, growing conditions, geographic location, condition at harvest, and storage conditions. Commercial feed enzymes (ß-glucanase) that break down ß-glucans in the diet are now available. The enzymes reduce the viscosity of the intestinal contents and improve bird performance.
Barley also contains phytic acid, which binds phosphorus and thus reduces phosphorus availability to the animal. Compared to other grains, however, the level of phytate in barley is less than that in wheat and oats, but higher than that in rye (Bartnick and Szafrańska, 1987). The enzyme phytase is needed to break down phytate and release the bound phosphorus. Poultry are not able to produce enough phytase. Cereals do contain some phytase since it is needed to make the phosphorus available to the embryo after germination. Phytase activity is very low in most feed ingredients although slightly higher in barley, rye, triticale, wheat, and wheat byproducts (Weremko et al., 1997). However, the phytase present has not been shown to increase phosphorus availability in poultry. Low-phytate barley varieties have been developed. The phosphorus bioavailability of these low-phytate varieties is 49%, compared to 28% in normal barley. When low phytate barleys are used in poultry diets, the need for supplemental phosphorus is reduced by 50% (Salarmoini et al., 1998). In addition, use of the low-phytate varieties has been shown to increase the bioavailability of other minerals such as zinc (Linares et al., 2007).
The main component of barley grain is starch, which is the main source of energy in grains. The level and availability of the starch will affect the energy content of a cereal grain. Barley has about 60% starch on a dry matter basis (Knudsen, 1997). Starch is comprised of linked glucose (a sugar) molecules connected together, and is referred to as a polysaccharide (meaning many sugars). The connection is via α-glycosidic links that are easily broken down in the digestive tract of birds and mammals. Polysaccharides are identified by the carbon atoms of each sugar involved in the link, as well as the type of linkage involved. There are two types of linkages–alpha (α) and beta (ß)–which differ in orientation of the oxygen atom involved in the linkage. The majority of the glucose linkages in starch are α-(1→4) linkages, although there are also a few α-(1→6) linkages. These α-(1→4) and α-(1→6) linkages are easily digested by the enzymes produced in the digestive system of animals. Animals are also able to digest the α-(1→2) linkages between glucose and fructose in sucrose, the ß-(1→4) linkage between glucose and galactose in lactose, and the α-(1→1) linkages between glucose molecules. Animals are not able to digest any of the other glycosidic bonds.
There are two main classes of cereal starches: amylose and amylopectin. They have different size, shape and composition. The glucose molecules of amylose are connected to each other in linear chains with α-(1→4) linkages. In amylopectin, the chains of α-(1→4) linked glucose are connected in a highly branched structure with α-(1→6) linkages between the chains. Amylopectin is easier to digest than amylose, so the digestibility of starch in a grain depends on the type of starch present. Normal barley varieties contain about 27% amylose and 73% amylopectin. Waxy starch varieties have lower amylose (2-10%) and higher amylopectin (90-98%) content. Digestibility of waxy starch in barley has been reported to be 10% higher than for normal starch (Ankrah et al., 1999), but waxy barley grains are typically smaller and contain less starch (Tester and Morrison, 1992). In addition, waxy barley varieties have also been shown to contain more ß-glucan than normal varieties (Ankrah et al., 1999).
The other source of energy in cereal grains is lipid. With 2-3% oil, the lipid content of barley is relatively low. Some cultivars, however, have been developed with increased lipid content. This increase in lipid is associated with increased lysine. The main fatty acid present is linoleic acid.
As with most cereal grains, the protein content of barley is low compared to legume seeds (Shewry and Tatham, 1990). Cereals contain three types of proteins: storage proteins, structural and metabolic proteins, and protective proteins. The majority of the proteins in cereal grains are storage proteins–in particular, prolamins and globulins. Prolamins are rich in the amino acids proline and glycine but are low in the essential amino acids lysine and tryptophan. Prolamins represent about half of the total protein present in barley, as well as corn, millet, rye, sorghum, and wheat. The primary prolamin in barley is hordein. Barley proteins are low in many of the essential amino acids including lysine, threonine, methionine and histidine.
The protein content of barley varies depending on the variety and growing conditions (Griffey et al., 2010). For example, 6-row cultivars are typically higher in protein than 2-row varieties. Nitrogen fertilization increases the protein content of barley grain, but the relative levels of the essential amino acids decrease.
While corn is typically used in poultry diets in the United States, Canada and many countries in Europe have been using wheat and barley for many years. Of course, the level of use will vary depending on the market prices and local conditions. Wheat and barley are lower in energy than corn, so it is common to add fat to poultry diets based on these grains in order to achieve the high dietary energy levels used in commercial poultry production (Adams, 2001). Such diets can increase the viscosity of the intestinal contents and increase the moisture content of the litter. Wet litter results in increased ammonia levels in the poultry house, as well as an increased incidence of breast blisters and hock burns on meat-type birds.
Nutritionists use nutrient composition tables to formulate least-cost rations that meet the nutrient requirements of animals. The wide variation observed in the energy content of barley, however, is not reflected in table values but needs to be taken into consideration when formulating diets. While many research reports in the literature are contradictory, it is generally recommended that unsupplemented barley should not be used in starter diets, and that the use of barley in poultry diets be restricted to 20%. The use of feed enzymes reduces the need for these restrictions.
The use of feed enzymes in barley-based diets reduces intestinal viscosity, thus improving the feeding value of barley. Enzyme supplementation also reduces the variation in feeding value seen with unsupplemented barley-based diets. Feeding barley cultivars of widely different ß-glucan levels give similar growth performance when supplemented with dietary enzymes. A variety of different feed enzymes are available that have ß-glucanase activity. Using enzymes also improves the litter quality of poultry raised on barley-based diets. Today, near-infrared spectrometry (NIRS) has made it easier to identify which batch of barley would benefit from enzyme supplementation and which would not. Near-infrared spectrometry is a rapid, computerized system that can be used for analyzing feed ingredients. It uses infrared light instead of chemicals for the analysis. The analysis requires that the system be calibrated for the particular ingredient being tested–so may be more expensive for some of the less commonly used ingredients–but has been routinely used in some feed mills for corn, wheat and barley.
Feeding whole grain in a complete feed has gained popularity in some regions as it can reduce feed-handling costs by eliminating the need for grinding. When using whole barley to replace all or a part of the grain in the diet, it is necessary to balance grains with the other ingredients so that the whole grain does not dilute the total nutrients consumed by the birds.
Feeding up to 20% whole barley to broilers had no negative effects on growth rate (Biggs and Parsons, 2009). Feeding 35% or more whole barley grain resulted in reduced growth and feed efficiency initially, but this reduced growth rate resulted in lower mortality and instances of leg problems.
Feeding 20% whole barley to turkeys resulted in an early reduction in growth rate (<1% reduction) as well as lower flock mortality and improved skeletal health (Bennett et al., 2002).
Reports of Bennett and Classen (2003) concluded that feeding whole barley (60%) blended with a mash concentrate to laying hens reduced egg production, feed efficiency, and shell quality while increasing feed intake, egg weight and body weight gain. They found this to be contrary to positive results found when choice feeding was used, and speculated that when the grain and concentrate are fed together, the hens can no longer accurately select intakes of whole grains and concentrates that meet their individual nutritional needs.
Brewer's dried grains are a byproduct of making wort or beer. They are also sometimes referred to as spent grain. They include cellulose and hemicellulose as well as the protein remaining after barley has been malted to releases its sugar for brewing. Sugars and starches in the original grain are removed during the brewing process so that the remaining spent grains are higher in protein but lower in energy than the original grain. The crude protein, oil and crude fiber content of the spent grains are about twice that of the original grain. The use of brewer's dried grains in starter diets should be less than 10%. Up to 30% can be used in grower diets, although the feed efficiency will be reduced. The restriction is due to the high fiber content of brewer's dried grains (Ademosun, 1973).
Malt sprouts are obtained from malted barley by removal of the rootlets and sprouts. They may also include some of the malt hulls, other parts of the malt, and foreign material. They must contain a minimum of 24% crude protein.
Nutrient content of malt sprouts (Batal and Dale, 2010)
This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.