CHAPTER FOUR
Feeding Chickens for Egg Production
Feed is an integral part of any production system, and raising birds in the best possible conditions is all for naught if the feed they consume does not provide the right nutrients at the right levels. While the general principles and ingredients are similar, feed formulations for different chickens do vary. This ensures that the birds receive the correct dietary building blocks in the correct quantities to maintain their health and, in the case of laying hens, to produce high-quality eggs in good numbers.
Over the years, poultry nutritionists have identified all of the nutrients required by chickens of various ages, purposes, and levels of production. With this information at hand, they have formulated diets that are considered complete feeds, providing all of the requirements on a daily basis. These feeds are marketed to small-scale producers as sack feeds, which can be given to chickens as the sole source of feed throughout their lives. They are split into three types depending on the age or productive stage of the chicken: starter, grower/developer, and layer.
Overall, this feed-management system has been termed “phase feeding.” With the system, chickens are not underfed or overfed, which improves their productivity in growth and egg production, and it addresses the cost of feed, thereby improving overall efficiency.
STARTER DIETS
Starter diets are fed to young pullets from hatch to about six weeks of age. Market chickens are often also fed chick starter throughout their growing period, from 6 to 10 weeks or so. However, chick starter is formulated for slow, sustained grow associated with laying chickens, not for the fast growth expected of a broiler. In some cases, starters that are specifically formulated for meat chickens and finishers, to be fed for the final two weeks or so before processing, can be purchased, which will support the much faster growth expected from a broiler chicken, hence increasing efficiency.
Generally speaking, starter diets contain the highest levels of crude protein, which ranges from 18 percent to 23 percent of the total diet for chickens. Starters with even higher protein levels (27–30 percent) are available for turkey poults and gamebird chicks. Starter feeds also tend to contain the highest levels of vitamins and trace minerals because of the higher requirements of these by fast-growing chicks, and the fact that the chicks can eat only small amounts of feed.
GROWER/DEVELOPER DIETS
These are fed to adolescent pullets aged from 6 to 18 weeks, just prior to point of lay. Most of the nutrient levels in grower/developer feeds tend to be either equal to, or lower than, those in starter diets. By the time these feeds are introduced, the growth rate of the birds has slowed and they are consuming enough so that the amount of each nutrient is adequate for their needs.
Layer diets are fed to pullets and hens during egg production. They are lower in protein than starter and grower feeds but slightly higher in many of the other nutrients. While the bird’s growth has essentially ceased, egg production requires higher levels of nutrients. Considering that the average hen lays about 20 dozen eggs each year, at an average weight of 24 oz. (680 g) per dozen, this works out as a total of 30 lb. (13.6 kg) of eggs, or at least six times the hen’s body weight.
The usual constituents of layer feed include protein (17 percent), fiber (4.5 percent), fat (2.5 percent), phosphorus (0.5 percent), sodium chloride (0.4 percent), sodium (0.1 percent), and various vitamins and trace elements. The high levels of calcium (3.5–4 percent) form high-quality eggshells and maintain bone health.
Some feed suppliers produce “all-purpose” feeds that can be fed to chickens of all ages, from hatch through egg-laying. While feeding all-purpose feeds makes life easier, producers must realize that these feeds are not ideal for birds at any age. As such, supplements will be needed to ensure that the birds get the correct nutrients, including oyster shell as a calcium source for laying birds (see here). If you do choose to use an all-purpose feed, read the label carefully and provide any required supplementation as directed, or poor performance or worse could occur.
NUTRIENTS VERSUS INGREDIENTS
When formulating diets, commercial feed suppliers use a variety of ingredients to supply the required level of nutrients. The nutrients are not added directly, but are included in various levels in the feed ingredients, which are then mixed in the proper ratios to provide the necessary levels. Common ingredients in poultry feeds include cereal grains for calories, including corn, barley, oats, and wheat; protein sources such as soy, canola, or animal products; and sources of other required nutrients such as limestone, dicalcium phosphate, fat, bonemeal, vitamin and mineral premixes, salt, and DL-methionine. The nutrient levels of each of the ingredients are known, so they can be mixed in the correct proportions to supply all the requirements for chickens at each stage of life.
The need for supplements
Even with all the technology and variety of feed ingredients to choose from, not all nutrients can always be added naturally. The essential amino acid methionine, one of about 20 amino acids that make up protein molecules, is one such nutrient. The common ingredients used in poultry feeds tend to be low in methionine, which results in slow growth and poor performance. This problem became particularly noticeable when most animal products were removed from poultry diets. To counteract this potential deficiency, synthetic methionine is now added to most poultry diets.
During feed formulation, nutrient levels, availability, and price are all taken into consideration. All available ingredients and their current prices are entered into a computer, along with the calculated levels of nutrients for the particular feed being mixed. Based on price and availability, the formulation of ingredients may change but the nutrient levels remain the same. This process is called “least cost feed formulation.” Before the advent of this process, feeds were mixed much less accurately, with nutrient levels only closely approximating requirements. This resulted in lower efficiency through overfeeding or reduced productivity through underfeeding. Other supplements, including scratch feeds, oyster shell, and grit, are discussed on here.
PROBLEM INGREDIENTS
“With every medicine there’s a little poison” is a saying that is also true of feed ingredients. Along with their nutrients, many feed ingredients contain naturally occurring compounds that can have negative impacts on chickens. Most are in small amounts or are degraded during processing so they don’t cause problems. However, some of these compounds can be quite toxic or interfere with digestion to the point that chickens don’t perform well. These compounds include: protease inhibitors, which reduce the digestion of protein; lectins, which bind to epithelial tissue, causing damage; tannins, which bind with proteins and carbohydrates, making them resistant to enzymes; phytates, which bind phosphorus and other minerals, requiring extra phytase to counteract the effect; and non-starch polysaccharides, which resist enzymatic action, causing increased gut viscosity and fermentation.
Even common feed ingredients such as soy and wheat contain one or more of these anti-nutritional compounds. Feeding raw soy, which contains fairly high levels of protease inhibitors, reduces the effective digestion of protein, reducing growth and egg production. However, during processing, temperatures reach levels that denature these inhibitors, rendering them non-functional and resulting in an excellent feed ingredient.
Foraging chickens are seeking seeds and insects. Their scratching behavior is a remainder from jungle fowl’s scratching through the leaf litter on the jungle floor.
Wheat has high levels of xylan, a 5-carbon sugar that forms complex hemicellulose compounds that tend to hold a lot of water. When ingested at high levels (30 percent and above), wheat in the diet therefore results in poor digestion and wet droppings. In recent years, synthetic xylase, the enzyme needed to break down these compounds, has been added to feeds to aid digestion, making wheat more attractive as a feed ingredient.
Some potential feed ingredients contain problem compounds that cannot be “fixed,” and so are not used in poultry diets. For example, dry beans such as pinto beans, kidney beans, and navy beans contain high levels of non-starch polysaccharides that can’t be digested effectively, resulting in some fermentation and gas production. The growth of chickens fed 30 percent bean meal is reduced significantly compared with those not fed bean meal. Heating the ingredients or adding enzymes are ineffective in fixing the problem.
Cottonseed meal is another potential feed ingredient and is often fed to dairy cows as a protein source. When fed to laying hens, however, the compounds gossypol and cyclopropenoid fatty acids contained within cottonseed can cause green, brown, or mottled egg yolks and pink albumen to form in the eggs. Research to develop low-gossypol varieties of cottonseed have been successful, but the cyclopropenoid problem persists. Therefore, cottonseed is not fed to poultry. Similarly, alfalfa included in the diet of layers at levels as low as 3 percent significantly increases the number of eggs with blood spots.
Canola (rapeseed meal), which is a member of the mustard family of plants, has the tendency to cause a fishy odor and taste in eggs with brown shells. Canola contains high levels of the choline ester sinapine, which is quickly converted to trimethylamine (TMA), a fishy-smelling compound. TMA oxidase, the enzyme that breaks down TMA into an odorless compound that is then excreted, is synthesized at only low levels by brown-shelled egg producers related to the Rhode Island Red breed, including many Production Red strains of layers. Another compound in canola is glucosinolate, which further reduces the effectiveness of the TMA oxidase, allowing the TMA to be deposited into eggs and resulting in the fishy odor and taste.
In light of this, it is clearly important that producers seeking alternatives to traditional feed ingredients consider the potential problems when using unknown ingredients. While such ingredients may appear ideal, there are generally reasons why they are not used in commercial feeds.
FEED INGREDIENTS BENEFICIAL FOR EGG PRODUCTION
The list of beneficial feed ingredients is shorter than the list of problem ingredients, but they can be used quite successfully. Both brewing and distilling grains—the “mash” remaining after the production of beer or distilled spirits—are effective ingredients that have been shown to significantly increase the thickness of albumen when as little as 10 percent of the diet comprises these grains. These products require drying before they are mixed into poultry feed, or they will cause it to mold quickly.
Corn oil in the diet has been shown to increase both egg number and egg weight in young pullets during their first eight weeks of laying. And excess amounts of the vitamins choline and B12 in laying diets have also been shown to increase egg weight.
In recent years, many small producers have chosen to use organic feeds. Organic poultry and egg production is one of the fastest-growing commodities in the organic marketplace, and there has therefore been a great deal of attention on organic feeds for these producers.
There are different definitions of what constitutes organic production. In general, however, all feed ingredients used in organic production systems must come from certified organic farms that control the use of certain fertilizers and pesticides. More recently, the use of genetically modified (GM) ingredients has also been controlled in organic production. Finally, the addition of some synthetic products, specifically amino acids, are not allowed (with some exceptions) in organic feed formulation.
In general, there is little difference in the nutritional value of a feedstuff that is produced under organic or traditional methods, so diet formulations have little to do with whether the grain is organic or not. The problem arises when considering availability. Less certified organic feed is grown, so these ingredients are harder to come by and consequently more expensive. Since the mid- to late 1990s, the proportion of GM corn and soy grown worldwide has increased steadily, to the point where more than 90 percent that is available can’t be used in organic diets. While there are adequate non-GM substitutes for corn that are available for organic feed, the same is not true for soy. Virtually all substitutes for soy are significantly lower in protein and/or contain anti-nutritional compounds that negatively impact chicken growth or egg production. To add to the problem, the inability to add synthetic amino acids, especially methionine, at appropriate levels further restricts organic feed formulation. Consequently, organic diets are either quite expensive (two to three times the cost of non-organic feeds), or they use less expensive ingredients from foreign sources that may be of questionable nutritional value and quality.
Now that some of the science of chickens and eggs has been presented, the “art” of chicken and egg production can be better understood. As noted earlier, chickens and eggs have been a part of the human experience for millennia, with the science of poultry and egg production about 100 years old. With much research and a great deal of trial and error over many decades, practices for the efficient production of high-quality eggs and birds have been established. In addition, in more recent years, understanding of proper bird welfare and food safety has created systems of production that provide for the birds’ well-being while at the same time producing high-quality, nutritious poultry and egg products.
Also note that while there are rules of thumb, chickens as a group are quite adaptable to various housing and management conditions. Therefore, as long as the basic necessities are provided, variation in methods can reflect any producer’s individual needs.
