The components of the poultry diet.
Poultry diets are primarily composed of a mixture of feedstuff such as cereal grains, soybean meal, fats, vitamins and minerals from a variety of sources as well as alfalfa meal or algae extracts. Some feeds may contain medications, growth factors and other microbials. If you want to see what I feed my hens just skip to the end of this article.
Chickens vary greatly according to the purpose for which they have been developed, those intended for the production of eggs tend to have a small and light body that requires less energy to look after and maintain whereas meat type chickens are bred with the tendency to fast growth and larger body size.
There is much more to the components of chicken feed than it's actual physical ingrdients. This article is an overview of the ingredients in chicken feed as well as their requirements.
This is a table graphic that I hope helps to explain the enegy requirement in poultry. This may seem odd as it is technically not an ingredient but the understanding of how it's used is important to the overall understanding of the feeding of chickens and other backyard poultry. Below is a breakdown of the needs of chickens and other poultry. The numbers below are specific to laying hybrid chickens and have been obtained by experimentation so can be used as general guidance for other poultry. The energy rquirements of males are considerably less.
Some studies were based on the simple premise that the better fed the hens the more eggs were produced so the number of eggs per unit feed has become somewhat of a standard in the laying hen industry. The broiler industry uses grams meat on the carcass per Kg of feed as a measure of the effectiveness of feed.
Energy use is further complicated by the fact that there are a great many inefficiencies in the metabolic systems of the bird. The gross (total energy) contained in the feed is broken down into digestible and metabolisable energy. What is left is net energy availiable to fuel the growth or wellbeing of the bird and in the production of eggs.
The study to calculate the energy requirements used standard analyitical procedures to work out the calorific content of the food before and after processing by the chickens. These studies started just after the second world war had finished (Fraps, 1946; Hill and Anderson 1958: Titus 1961) and are based on a kilogram of food, ie 4000kcal per Kg of poultry (not necessarilly always chicken) feed. (Scott et al, 1982 studied the effect of species, genetic makeup, age of the poultry and enviromental conditions in a wider ranging study)
Interestingly one of the issues the study over productive energy ran into over the 5 day test period when they tried feeding the test subjects a single feedstuff it initially caused palatability problems and errouneous results which were reduced by adding a second component to the diet even though this led to greater variability in the final results.
One of the first to conduct extensive studies of energy utilization with chickens was Fraps (1946) who showed that available energy was related to the fiber content of feedstuffs. Heuser et al. (1945) and Bird and Whitson (1946) reported that rations containing fibrous ingredients such as oats and wheat by-products were the least efficient for egg production.
Scott, Matterson and Singsen (1947) showed that an efficient broiler ration, if properly supplemented, could be formulated with high levels of corn. The acceptance of high-efficiency starter diets stimulated the development of similar diets for adult stock.
Quisenberry, Sherwood and German (1949) and Singsen, Matterson and Kozeff (1950) in comparing a conventional ration with a high corn ration found that the latter produced more eggs per unit of feed consumed. Bearse, Berg and Miller (1950) reported that the energy content of growing and laying rations had no effect on egg weight or hatchability. This was quite interesting as it proved that hens that are undernourished just lay less eggs rather than smaller ones.
Dietary carbohydrates are the important source of energy in the poultry diet. In the commercial type products these are obtained from cereal grains like wheat, barley, sorghum and maize and occur mainly as starches which are easily digestible. There are other types of starches called polysaccharides which are not easily metabolised and are relatively useless to the chickens diet.
Proteins and amino acids:
We might call them proteins but really the need is for amino acids of which there are 22, all of which are physiologically essential. Amino acids fall into 2 catergories, non-essential, or those which can be converted or synthesised in the body and, essential amino acids, or those that cannot, like methionine, that have to be present in the diet in minimum quantity.
I'm not going to go into the list of amino acids and their relationships to each other, that is the subject of another article I will be publishing very soon. There is also relationships between some of the amino acids, some rely on each other while at least two are antagonoistic and in surplus several are toxic.
Thanks to the layer and broiler production that make up the modern poultry supply chain considerable research has been done into the production of meat and eggs for the absolute minimum of cost and waste.
Fat is generally added to chicken feed to increase the enegy content of the feed, this is mostly for broilers or meat chicken production but needs to be limited to prevent the collection of fat on the carcass or lipid accrual. Fat is essential for the chicken diet as it is for most diets, some vitamins for example are fat soluble.
Depending on where you are in the world Feed grade fats may come from rendering of animal carcasses or vegetable oils not suitable for human consumption. Fats also oxidize over time limiting the storage potential of food and too much fat in the feedstuff may give tastes to the eggs, fishy tasting eggs are often associated with to much fats in the diet.
Minerals are the inorganic parts of the diet and again are divided into two groups on the basis of their needs within the body. Whilst major defiencies are rare, especially in free ranged hens, minor shortages of minerals are quite common in chickens, espeially if they are confined, there is little commercial point in spending money buying feed with expensive additives that improve hatchability if you only supply eggs to a shop, much better to buy a feedstuff that produces nice yellow yolks for the consumer market.
Minerals are very important for the formation and ongoing condition of the skeleton and bodily systems. Iron for the heam molecule in blood and the like.
Macro minerals are shown as a percentage (%) of the diet and these include calcium and sodium.
Micro or trace nutrients amounts are given in milligrams (mg) per kilogram (Kg) of body weight. These are typically essential trace elemnts like iodine, iron, selenium and copper.
There is a need for balance within limits in the amounts of minerals in the diet of hens and other poultry. An excess of calcium can interfere with the absprbtion of other minerals like phosphorus
Vitamins fall into two categories, fat soluble like A, D, E, and K and water soluble vitamins like the B complex and vitamin C. The quantities are expressed in IU (International Units) or milligrams per kilogram.
For a detailed article on vitamins in poultry take a look here.
Water is an essential nutrient and whilst precise requirements are very difficult to determine as they depend on age, external conditions like temperature and feed, the breed and sex of the bird as well as the efficiancy of the reabsorbtion of water in the kidneys. Higher protein increases water consumption, studies have given averages of 213ml in 24hours with 116g of commercial feed ration.
I have written an article about the importance of water to poultry before.
You need to remember that commercial chicken feed is produced down to a price point with the cheapest ingriedients to produce the most profit for the company producing it. When deciding what ingredients to put in the feed the company will base it's desition on what is availiable and cheap and not necessarily on what is suitable or best for poultry. Often the feedstuff is bulked out with dust from other production processes and inferior quality grains like water spoiled or sprouted wheat or barley.
Also bear in mind that pellets may contain upto 6% ash as a bulking agent.
Commercial layers feeds also contain colouring agents called xanthophylls to colour the yolks of the eggs.
So what's in my chicken feed I hear you ask? I have a special blend made up by my feed merchants.
It contains by weight 40% Massey (UK feed Suppliers) layers pellets, 22% whole wheat, 22% Split maize (cracked corn) 4% kibbled barley, 4% rolled oats, 4% shell and grit, 4% whole sunflower seeds and most importantly they free range over 4 acres. The hens always polish it off with nothing left.
I did quite a lot of experimantation over 4 years to work out what my hens liked. I did choice testing where the birds are given several different types of feed an I think the most important thing I have taken away from it all is that they like variety.