Written by: Dr. Jacquie Jacob, University of Kentucky
Barley (Hordeum vulgare) is commonly grown for malting but can also be grown for human food and animal feed. Barley is the main feed ingredient in some parts of western North America and in many countries in Europe that are less suitable for corn. In addition, barley can also be grown as a pasture crop and can play an important role in crop rotation in organic production systems. Barley has an extensive root system that makes it able to compete with weeds. Barley is often used to break disease, insect, and weed cycles associated with other crops. Direct rotation with other small grains, however, is not recommended.
Barley can be added to an animal feed as an energy source, with some restrictions. Poultry cannot digest barley’s carbohydrates as easily as those of corn because of the amount of non-starch polysaccharides (NSPs) in barley. The carbohydrates of corn grain are typically 65% to 70% starch and 11% to 14% fiber. In contrast, barley grains typically contain 60% starch and 22% fiber. As early as 1928, reports described the poor performance of birds fed barley-based diets. The poor performance was originally believed to be because of barley’s high fiber content, but hull-less barley cultivars show similar performance levels to that of the hulled cultivars. The antinutritional factor identified in barley grain is beta-glucans (ß-glucan), which, because of its chemical structure, cannot be easily digested by poultry. The beta-glucans bind with water in the intestine, resulting in the formation of gels and increasing the viscosity of the intestinal contents. The increased intestinal viscosity reduces the availability of the nutrients in the diet. It can also cause sticky droppings resulting in increased incidences of ‘pasty butt.’
Commercial feed enzymes are now available that can break down the beta-glucans in the diet, reducing intestinal viscosity, increasing nutrient availability, and improving bird performance. The effectiveness of enzyme supplementation, however, is influenced by the age of the bird as well as the barley cultivar used and the conditions under which it was grown. Older birds are more able to utilize barley than young chicks.
Barley also contains phytic acid. This compound binds phosphorus during digestion, reducing its availability to the animal. Varieties of barley that are low in phytic acid are now available, decreasing the need for supplemental phosphorus in poultry diets. Commercial phytase, a feed enzyme that can be added to poultry diets to improve the availability of phytate-bound phosphorus, is also available.
Nutrient composition tables allow nutritionists to meet animal needs with a combination of ingredients. However, energy values for barley can vary widely and a given nutrient table might not reflect the true values of the barley a producer uses. Beta-glucan levels in barley are affected by the cultivar, growing conditions, geographic location, conditions at harvest, and storage conditions. The age of the animal consuming the feed is also important. The digestive tract becomes more efficient as the animal ages, permitting older birds to utilize barley more effectively.
Average Nutrient Content of Barley
- Dry matter: 89%
- Metabolizable energy: 2750 kcal/kg or 1250 kcal/lb
- Crude protein: 11.5%
- Methionine: 0.18% (79% available)
- Cysteine: 0.25% (81% available)
- Lysine: 0.30% (78% available)
- Tryptophan: 0.17%
- Threonine: 0.36% (77% available)
- Crude fat: 1.9%
- Crude fiber: 5.0%
- Ash: 2.5%
- Calcium: 0.08%
- Total phosphorus: 0.42%
- Non-phytate phosphorus: 0.15%
There are several different varieties of barley, and they can be classified in a number of ways.
- Barley varieties can be classified on the basis of head type. There are two-row and six-row varieties—the number of rows refers to the rows of seeds on the stalk of the plant. The two-row varieties are grown primarily in Europe. The six-row varieties are commonly grown in the United States. Six-row varieties are typically higher in protein and lower in starch than two-row varieties.
- Barley varieties can also be classified on the basis of growth habits. There are winter and spring types for both the two-row and six-row barley varieties. The seedlings of winter barley must be exposed to cold, which enables the barley to produce heads and grains normally. Winter barley is usually sowed in the fall so that it will be exposed to low temperatures during the subsequent winter. Spring barley does not require exposure to cold temperatures, so it can be sowed in the spring and summer.
- Spring barley can play an important role in crop rotation with nongrain crops. The barley tends to break disease, insect, and weed cycles associated with other crops.
- Waxy and normal barley varieties differ in the composition of the starch in each variety. The level of amylose to amylopectin is an important characteristic that effects malting, food, and feed value. Normal barley varieties have a starch content of about 27% amylose and 73% amylopectin. Waxy barley varieties have lower amylose (2% to 10%) and higher amylopectin (90% to 98%) content. Amylopectin is easier for poultry to digest than amylose. As a result, waxy barley has a higher energy content than normal varieties.
- Barley is typically eaten after the inedible, fibrous outer hull has been removed. Once the hull has been removed, the grain is referred to as “dehulled” barley. Dehulled barley still has its bran and germ. Pearl barley is dehulled barley that has been steam-processed to remove the bran. The proportion of hull to kernel can differ widely between varieties. The result is a wide variation in the energy content. Dehulled barley should not be confused with hull-less or naked barley varieties.
- Hull-less or naked barley is closely related to hulled, or covered, barley. Hull-less barley looks like hulled barley while it is growing, but as it begins to mature the hull loosens. During harvesting, the hull is removed completely. Hulled barley contains 5% to 6% crude fiber, whereas the fiber levels of hull-less barley are similar to those of wheat and corn. Both hulled and hull-less barley contain beta-glucans. While the available energy content of hull-less barley is less than that of corn, it is superior to hulled barley. The available energy of hull-less barley is similar to that of wheat, but the substitution of barley for wheat in the diets of broiler chicks has been shown to result in reduced three-week body weight.
Although 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. Corn requires a longer growing season and cannot tolerate frost periods as well as wheat and barley can. Tradition and culture also influence where these crops are grown.
The level of barley use varies depending on market prices and local conditions. Wheat and barley are lower in energy than corn, so it is common to add fat to poultry diets that rely on wheat and barley in order to achieve the high dietary energy levels required 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 determine how to meet the nutrient requirements of animals at the least cost to producers. However, table values do not reflect the wide variation observed in the energy content of barley, although producers must consider this energy content when formulating diets. Many research reports in the literature are contradictory, but it is generally recommended that unsupplemented barley not be used in starter diets and that the use of in poultry diets be restricted to 20% barley content.
The use of feed enzymes reduces these restrictions. The use of feed enzymes in barley-based diets reduces intestinal viscosity, improving the feeding value of barley. Enzyme supplementation also reduces the variation noted for the feeding value. Feeding barley cultivars of widely different beta-glucan levels gives similar growth performance when supplemented with dietary enzymes. Enzymes also improve the litter quality of poultry raised on barley-based diets. Today near-infrared spectroscopy (NIRS) has made it easier to identify which batches of barley would benefit from enzyme supplementation and which would not.
Feeding whole barley
Feeding, unground, whole-grain barley has become more popular in some regions to reduce feed-handling costs. Feeding a diet composed of 20% whole barley to turkeys has shown no negative effects on growth rate. Feeding a diet composed of 35% or more whole barley initially resulted in reduced growth and feed efficiency. This reduced growth rate, however, resulted in reduced mortality and leg problems. The feeding of grit is not necessary when feeding whole barley to turkeys.
Feeding whole grains to laying hens was shown to reduce egg production, feed efficiency, and shell quality while increasing feed intake, egg weight, and body weight. The effect was the same whether the hens received grit or not.
Feeding barley by-products
Brewers dried grains
Brewers dried grains are a by-product 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 release 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 contents of the spent grains are about two times that of the original grain. Brewers Dried Grains can be included at 10-20% in poultry diets.
Malt sprouts are obtained from malted barley by removing the rootlets and sprouts. Malt sprouts may also include some of the malt hulls, other parts of the malt, and foreign material. Malt sprouts must contain a minimum of 24% crude protein.
FOR MORE INFORMATION
Sticky droppings: A feed-related poultry problem. Carol Miles and Sacha Johnson, Washington State University.