Poultry regulate their intake of feed based on the energy content of the feed. The higher the energy count, the less they eat. It is important to ensure that chickens eat enough to get all the required nutrients from their feed. Gaining body fat is not a problem in today's poultry breeds, which are bred for extremely high growth and efficiency. Egg-laying chickens require ~500 kJ / day for maintenance, or 770-840 kJ ME/day. Each kilogram of eggs produces requires 11,2 kJ ME. Young egg-laying hens need additional 10 kJ a day for their own growth.
Methods of determining energy content
|Chickens in balance cages (c) ILVO|
The Farrell method is a more rapid determination of ME. In the beginning and end of the collection period, the animals are denied food to increase the reliability of the test results. Farrell method uses only experienced test animals, which are able to eat high amounts of test feed in one hour. 24 or 36 hours after the animal has eaten ,the feces (including the uric acid) are collected and analyzed. The Farrell method is a lot faster than CAM, and requires the animals to spend only a short time in the balance cage. However, fasting is unnatural for poultry, which may raise welfare concerns.
The third method is the Sibbald method. Unlike Farrell and CAM, Sibbald is used to determine the true metabolizable energy. The animals are kept on a fast for 24 hours before the trial to empty their digestive tract. The test feed is then force-fed through a tube directly into the crop of the birds. 25-50 grams of feed is inserted at one time. Feces are collected 24 or 48 hours after the force-feeding. To determine endogenous excretion of nitrogen, the trial is repeated several times, and each time one animal is not fed at all. The results for that animal show the level of endogenous excretion. While the Sibbald method is fast, reliable and enables studying all kinds of feeds, it raises severe welfare concerns due to fasting and force-feeding.
Amino acidsLike mammals, poultry need to get necessary amino acids from their feed. Young chickens need amino acids more than older ones, since their growing feathers, meat and bones require a lot of protein. The most needed amino acid is lysine. Young chickens need lysine 9,5 g/kg. Because poultry regulate their intake of feed based on the energy content, it is important to make sure they eat enough to get the needed proteins. To estimate this a ratio between energy content and amino acids is calculated:
amino acid content / energy content = AA/energy ratio
For a 6 week chick the ratio should be 155-160 g / 10 MJ, 165-180 g / 10 MJ for a meat chickens and 140-150 g/10 MJ for egg-laying hens. The feed for chicks younger than 6 weeks should have 200 grams of protein / kg dry matter.
The ideal protein for poultry is a bit different for meat chickens and egg-laying hens. Lysine is the most important amino acid for both. Layers need more amino acids than meat chickens. The exceptions are histidine, leucine, phenylalanine and tyrosine, which are more important to meat chickens than layers. Layers need amino acids in relation to their weight and egg production capability. For example, a layer needs 9,99 mg lysine a day / g of eggs produced, and further 73 mg / weight in kg. A 2 kg chicken laying one 60 g egg would thus need 9,99*60 + 73*2 = 745,2 mg lysine / day.
Meat chickens should be fed in phases to optimize their utilization of lysine. The need for lysine decreases as the meat chicken grows, so each feeding phase can contain less lysine. Optimizing feeding for meat chickens and layers decreases feed costs and waste of nitrogen.Varying the phase feeding lengths for meat chickens can increase the weight at slaughter over 150 grams, and decrease the amount of abdominal fat 0,5 %.
Studies show that optimizing poultry feeds based on amino acids is more reliable than optimizing based on metabolizable crude protein. Optimizing amino acids can produce 18-24 % less nitrogen in feces and better utilization of amino acids in the feed.
|(c) Ultra Bio-Logics|
Egg-laying hens have strict requirements for minerals in their daily feed. Lack of minerals in the beginning of the laying season may affect productivity for the rest of the season. Layers need especially
- Calcium: needed for bones and egg shells. Calcium is important for chickens of all ages.
- Phosphorus: calcium and phosphorus must be in the right balance for either to work. Phosphorus is also important for vitamins and cell metabolism.
- Magnesium: activates enzymes in energy metabolism, and builds up nerves and bones. Magnesium is said to have a calming effect on chickens.
- Sodium: Balances the nervous system and pH
- Chloride: Balances the fluid balance of the body, is needed for gastric juices
- Potassium: A balancing factor
- Sulphur: Important for building sulphur-based amino acids, and for healthy feathers
|(c) Beaverhausen's Blog|
When the egg shell forms, calcium ions are combined with HCO3-. HCO3- is originally created from water (H2O) and carbon dioxide, CO2. When the Ca++ and HCO3- are mixed, a nitrogen is lost and the resulting CaCO3 creates a sturdy, white egg shell.
Phosphorus and phytic acid are important in maintaining good layer productivity. In one study a feed with 3 g P/kg and no added phytic acid results in a laying rate of 92,4 %, egg weight of 56,8 g and dry matter content of the tibia of 4,19 g. The same feed with 460 units of added phytase resulted in a laying rate of 95 %, egg weight of 58,4 g and dry matter content of the tibia of 4,87 g. Another study has proven that adding phytase increases the utilization of inorganic phosphorus, but do not improve the apparent ileal digestivity of P. Added phytase also increases the mineralization and tensile strenght of bones.
FeedsChickens are usually fed either with a complete feed or concentrated feed + grains. Complete feeds include everything the birds need: minerals, proteins, energy, fats and calcium. It is an easy but expensive alternative. Using concentrated feed and grains requires more planning, but can be cheaper if home-grown grains can be used. All ingredients must be analyzed to ensure their correct balance in the feed, and mixed well. The ratio of ingredients must be changed throughout the growth/egg-laying period as the requirements of the animals change.
In Northern Europe, the most important ingredients in poultry feeds are barley and oats. They contain noticeably less energy than soybeans and corn, which are commonly used in the USA and elsewhere. Vegetable oils can be added to the grains to increase the energy content, because poulty cannot eat very much at one time, and will lose weight if the feed is too low in calories. 70-80 % of the energy in grains is metabolizable, because the energy in grains is mostly starch. Wheat has 65 % of starch, barley 55 % and oats 40 %. Poultry can metabolize starch almost entirely.
|(c) Fowl Visions|
Soybean meal has 50 % of protein and much lysine, but it has to be supplemented with methionine. Soy can be used for meat chickens. Rapeseed meals (canola) are the "left overs" from the production of rapeseed oil. Depending on the oil production method, rapeseed meals contain 2-10 % fat and roughly 8 MJ/kg ME. The protein content is similar to soybean meals, but is less digestable. If the rapeseed used contains no erucic acid, sinapic acid or glucosinolates, rapeseed meals can be used to replace soybean meals entirely. However, in one study canola meals were found to decrease egg-laying percentage and egg weight.
Peas and broad beans have some antinutrients, such as oligosaccharides (pea), visine and convisine (broad bean). Visine and convisine cause aplastic anemia, which is uncurable and lethal to chickens. The amount of visine and convisine in broad beans cannot be reduced in feed processing. Peas have 20-22 % of protein and broad beans 26-28 %, and both have a lot of lysine but little methionine. Due to the antinutrients, the feed of layers can have up to 30 % peas and 5 % broad beans.
Fish meal is used for chicks in small amounts. Adult layers and meat chickens develop a fishy taste and smell to eggs and meat if fed fish meals.