1 . Feed formula design requirements for laying hens

　　The design of laying hens' feed formula is required to be scientific, reasonable and make full use of new knowledge and achievements in the field of animal nutrition. On the premise of satisfying the nutritional needs of laying hens in each growing period and ensuring the egg production, feed formula design should consider the feeding cost, scientifically and rationally utilize all kinds of raw materials and eliminate the use of all kinds of prohibited drugs and feed additives.

　　2 . Feed formula design for laying hens

　　2.1 The concentrated material is usually 30%~50% concentrated material in the feed formula of egg chicks, 30%~40% concentrated material for breeding chickens and 35%~40% concentrated material for laying hens. The calculation methods of the concentrated material amount can be calculated from the compound feed and calculated from the set proportion. The user can use the concentrated material according to the recommended dosage of the feed enterprise. When the feed raw material changes, the ratio calculation should be carried out again. It is a common problem to ignore the digestibility of feed raw materials, and the amount of miscellaneous meal such as cotton meal and rapeseed meal should not exceed 5% of the total feed amount in general.

　　2.2 Amino Acid In order to ensure the stable and high yield of laying hens, the balanced diet can be configured according to the digestible amino acid amount of laying hens, so as to make the content of various amino acids in the diet consistent with the maintenance amount and production requirements of laying hens, and make the maximum conversion rate of feed, and reduce the excretion of nutrients.

　　2.3 Enzyme preparation can accelerate the degradation of nutrients in the chicken body, and can degrade the macromolecules which are not easy to be absorbed by the chicken body into the small molecules which are easy to be absorbed, which can promote the digestion and absorption of nutrients and improve the utilization rate of feed.

　　Plant enzymes can make use of phosphorus phytate in feed materials, thus reducing environmental pollution caused by manure.

　　2.4 Many Chinese herbal medicine additives have the functions of soothing qi, calming nerves, deworming, eliminating heat and detoxification, sterilizing and reducing inflammation, which can promote the metabolism of laying hens, enhance disease resistance and improve feed conversion rate.

　　3 . Notes for designing the formula

　　Some feed raw materials contain some toxic and harmful substances, we should pay attention to the design of feed formula.

　　3.1 Rapeseed cake contains more than 35% crude protein and 27.8% digestible protein, which is a kind of high-quality protein raw material. However, the glucosinolates contained in the rapeseed cake can be hydrolyzed into toxic isothiocyanate, azolidinthione, nitrile, etc. If the rapeseed cake is fed directly without proper treatment, it is easy to cause poisoning. The toxicity of rapeseed cake is related to the varieties of rapeseed. The tolerance of different varieties of layers to rapeseed cake is also different. The common rapeseed cake accounts for 8% of the feed of laying hens and 10% of the feed of broilers in the later feeding period can cause poisoning.

　　Toxic layer chicken intake decreased, dry or thin feces, some of the feces with blood, its growth is slow, egg production decreased, soft shell eggs increased. Autopsy lesions are goitre, gastric mucosa congestion or bleeding, renal enlargement, liver atrophy, smooth, digestive tract (especially stomach) content is thin, black green, intestinal mucosa abscess, bleeding.

　　The feed containing rapeseed cake should be stopped immediately after the discovery of rapeseed cake poisoning, and the poisoned chicken should drink 5% glucose water and add VC into the feed. For laying hens under 6 weeks of age and broilers under 4 weeks of age, rapeseed cake should not be used in the usual ingredients. For other chickens, the proportion of rapeseed cake in the feed should not exceed 5%.

　　3.2 Excessive amount of cottonseed cake harms the protein content of cottonseed cake more than 36%, its amino acid content is second only to soybean meal, is an economical protein raw material, but it contains gossypol. Feeding cottonseed cake for a long time or a large amount of laying hens will cause poisoning if gossypol accumulates in the chicken body in excess.

　　Anorexia, emaciation, soft legs, weakness, diarrhea, light feces, dyspnea, the eggs produced by the poisoned chicken become smaller, the white turns pink, the yolk turns tea-green, the hatching rate of the eggs decreases. Necropsis revealed hepatomegaly or atrophy of the kidney, dilated gallbladder, exudate in the chest and abdomen, dark brown of intestinal contents from front to back, shedding and bleeding of intestinal mucosa, waxy deposits on liver, spleen, pancreas, intestinal mucosa, and high atrophy of laying ovary and each section of fallopian tube.

　　To prevent cottonseed cake poisoning, detoxification should be carried out before feeding cottonseed cake, which can be boiled for a few hours or soaked in 0.2%~0.5% ferrous sulfate solution for 24h. The amount of cottonseed cake in the feed is generally below 5%, the amount of laying chicken does not exceed 7%, the planting chicken, chick had better not feed cottonseed cake. It is better to increase the amount of protein, VA and calcium when using cottonseed cake ingredients. After the discovery of chicken cottonseed cake poisoning, should quickly change the feed, and add ferrous sulfate powder in the feed, at the same time to the poisoned chicken drinking 5% glucose water or licorice, tea, mung bean with boiled soup, can also be added in drinking water soybean milk, milk or quoted 0.02%~0.03% potassium permanganate liquid.

　　3.3 The harm of excessive salt Salt is an indispensable component in chicken diet, its content is generally 0.3%~0.4%. Chickens can quickly become toxic when they eat too much salt. Chickens are most sensitive to salt overdose. When the salt in general chicken feed reaches 0.7% and the salt in adult feed reaches 1%, obvious thirst and diarrhea can be caused. When the salt in chicken feed reaches 1%, a large number of chickens will die.

　　Symptoms of chicken salt poisoning vary with the amount of salt consumed and the duration of salt intake. Symptoms mild increase of drinking water, waste thin, serious feathers loose, light, highly excited, nervous, chirping and scrambled to water, loss of appetite, or craw soft expansion, spat sticky secretions outflow, before and after his weak legs, or horizontally, backward movement, back a few steps that collapsed on the ground or to a side movement or stand aside. Some sick young spirit depressed, bow back neck, drooping head closed eyes, late watery diarrhea. The poisoned chicken died of paroxysmal spasm, wings extended, beak landing, collapse. Autopsy dead chicken see subcutaneous edema or a light yellow glue sample infiltration, chest, leg muscles diffuse hemorrhage, abdominal cavity there is a lot of water, water with pale yellow, pale and mixed with fibrin exudation, crop product has a lot of mucus, glandular stomach mucosa congestion, some form of false film, small bowel acute catarrhal enteritis or hemorrhagic enteritis, liver color light, swelling, margin obtuse, very brittle, blood clots, liver capsule attached most cases hepatic parenchymal atrophy, its surface is uneven, harden and gallbladder shrivel, epicardial capillaries expansion or bleeding, pericardial effusion, pulmonary edema, light color, meningeal edema and hyperemia or cerebral cortex.

　　Chicken salt poisoning should immediately stop feeding the original feed, feed more young green leaves, and provide adequate, fresh drinking water or 5% glucose water and 0.5% potassium acetate solution, even drinking 3D. To prevent the poisoning of chicken salt, the salt content should be calculated correctly and mixed evenly. The salt content of the dried fish or fish powder used in the ingredients must be determined, and the high salt content should be added less.

　　When finding abnormal drinking water of chickens, salt determination should be carried out on the feed. Toxic chicken timely isolation, feed brown sugar water, increase the dosage of a variety of vitamins, conditional can inject glucose and VC.

　　3.4 Fluoride is a necessary trace element for animal body, but long-term feeding of mineral additives without defluorination treatment, such as calcium superphosphate, can cause fluorosis of livestock and poultry. Most calcium and phosphorus supplements in chicken diet are mineral phosphate (mainly calcium hydrophosphate), which contains a certain amount of fluorine and is easy to cause chicken fluorosis.

　　Fluorosis chickens, loss of appetite, spirit is depressed, growth retardation, thin, weak legs, joint swelling, gait instability, movement disorders, feet soft, sometimes a foot "eight" word, severe lameness or paralysis, diarrhea, some died of diarrhea, cramps, failure, layer chicken egg production decline after the poisoning, the smaller eggs, hatching eggs, sand shell eggs, deformity. Fluorosis of breeding chickens can reduce fertilization rate and hatching rate and cause leg deformity of fresh chicks. Autopsy results showed that the liver of the diseased chicken was slightly swollen, with light color and yellowish brown, with blood stasis and edema in the lungs, slightly swollen kidneys, brittle texture, a small amount of urate deposition in the ureter, congestion and bleeding of the intestinal mucosa, severe intestinal mucosa peeling, and brittle bones of the diseased chicken.

　　The chicken that has produced fluorosis should undertake treating in time. When fluorine poisoning is found in chickens, it is necessary to stop feeding fluorine-containing feed immediately, and to feed the chickens with reliable quality full price feed, and to provide fluorine-free drinking water, in which hydrated lime is added. Feed can be added calcium lactate, VA, VD3 and other vitamins, until the chicken claudication symptoms disappear. Calcium preparation can also hinder the fluoride in the bones, increase the calcium in feed, while the supply of VA, VD to prevent fluorine poisoning effective.

　　When supplementing animal feed with phosphate mineral substances, the fluorine content should be exactly known and defluorinated, and the supply should not exceed 2% of the daily diet. Bone meal produced in some areas is sometimes high in fluorine and should not be used as a mineral supplement.

　　In feed production, product quality and the formula design there is a certain difference phenomenon, thus nutritional composition and granularity of deal with raw materials, mixing uniformity, batching accuracy, material production, finished product moisture, material residues, sampling, testing and so on eight big analyzing every factor affecting the quality of feed products, adjustment, in order to make the theoretical value in conformity with the actual situation.

　　4 . Tips for designing feed formula for laying hens

　　4.1 Adjust the formula according to the raw material price in time To make clear the raw material price is the stock price or the market price, is the forecast price or the average price, should adjust the formula according to the change of raw material price in time, in order to reduce the formula cost.

　　4.2 The crude fiber content in the feed was controlled: 2%~3% for chicks, 5%~6% for bred chickens, 2.5%~3.5% for laying hens, and the general dosage was controlled below 5%.

　　4.3 The feed volume should be suitable for the digestive tract of laying hens. Too large feed volume can cause the digestive tract burden of laying hens and affect the digestion and absorption of the feed. However, when the feed volume is too small, even if the nutrition is enough, the laying hens still feel hungry, which is not conducive to the normal growth and egg production of laying hens. Therefore, it should be paid attention to make the volume of feed adapt to the volume of the layer's digestive tract.