Nutritional Deficiencies in Chickens

Recognize Nutritional Deficiency and Provide the Right Foods

Nutritional Deficiencies in Chickens

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Nutritional deficiencies in poultry used to be more common, enough that we have a fairly good knowledge of the common deficiencies. These nutritional deficiencies are not seen as much anymore because commercial chicken feed is very carefully balanced to supply everything that a chicken needs even through different stages of growth. However, when you start feeding treats or scraps to your chickens or allowing them to free-range, this carefully balanced diet can be thrown off. Here are some of the more common nutritional deficiencies that you may encounter in your flock.

Vitamin A — A deficiency in vitamin A can have signs such as cheesy, watery discharge from the eyes, the birds growing extremely thin and weak, ruffled feathers, discharge from the throat, decrease in egg production, and the possibility of eyelids becoming stuck together. Deficiency can be from lack of adequate intake or from other factors affecting absorption. Rancid fats in their feed can oxidize the available vitamin A. Also neomycin, an antibiotic, can decrease absorption. Many colorful or dark green vegetables are high in vitamin A as well as animal products such as dairy and beef liver. Several orange fruits are high in vitamin A; these include cantaloupe, apricot, and mango.  


Vitamin D3 — A deficiency in vitamin D3 causes rickets and caged layer fatigue. Because vitamin D is needed for the metabolism of calcium and phosphorous, a deficiency causes problems with bones in young chicks and eggshell formation in laying hens. Signs include bowed legs causing the chick to have trouble standing or walking as well as deformed legs and beak. Laying hens may suffer from low bone density, have soft or thin-shelled eggs, or small eggs. If caught early and supplemented, this can be reversed. Symptoms occur more often with caged layers rather than those able to walk around, likely because exercise and weight-bearing help with bone density. Adequate direct sunlight (not through a window) helps a chicken to make their own vitamin D. An excess can cause calcium pimples on eggshells. 

Vitamin E — Encephalomalacia, or a softening of the brain, is the clinical symptom of this deficiency. Other signs include tremors, incoordination, and rapid contraction/relaxation of the leg muscles. Deficiency might occur because of old feed (it degrades over time), the feed overheating and destroying the vitamin E, or by a deficiency of selenium. Supplementation is best done through feed or drinking water rather than a single oral dose. 

Vitamin K — Because vitamin K is essential to blood clotting; a deficiency is likely to cause hemorrhage and anemia. A diet deficiency or the use of sulfur medications such as sulfaquinoxaline (a coccidiosis medicine) can cause this. The best supplementation comes from menadione being added to feed at a rate of 1–4 mg/ton for prevention, double for treatment of a deficiency. (Leeson, 2015) 

Vitamin B1 (Thiamine) — Thiamine is essential in converting carbohydrates to glucose for nervous system function, therefore a deficiency often shows signs connected to the nervous system. These signs can include lethargy, weak legs, head tremors, decreased appetite, paralysis, lowered body temperature and respiratory rate, and “star gazing.” Causes include dietary deficiency, overuse of coccidiosis medication, or the presence of thiaminase enzymes (enzymes that cut apart thiamin) such as in poorly processed fish meals. When in a severe deficiency, chickens may need to be force-fed or injected with thiamine. 

Vitamin B2 (Riboflavin) — This deficiency is marked by curled-toe paralysis as its main sign. There are different degrees of severity of the curled toes from mildly curled toes and chicks tending to rest on their hocks to completely curled toes with legs that are so weak that the chicks tend to walk on their hocks with wings helping. Other chick symptoms include a failure to grow, diarrhea, and high mortality within three weeks. Poults experience skin dermatitis and an encrusted and inflamed vent before dying. In hens, egg production decreases and hatchability drops remarkably. Leafy green and dairy products are good sources to supplement riboflavin. 

Iron — Too little iron causes anemia, but the most obvious sign will be a loss of pigmentation in the feathers of colored breeds. Reduced absorption of iron can be caused by certain mycotoxins in the chicken’s feed, namely ochratoxin and aflatoxin. 

Zinc — Zinc is a trace mineral of which your chickens only need a tiny amount. However, a deficiency can cause shortened, thickened leg bones with enlarged hocks, frizzled feathers, and stunted growth. A deficiency is likely to be caused by a diet high in soybeans, excess selenium, calcium, or phosphorous as they can block the absorption of zinc. A zinc deficiency should be confirmed by your veterinarian because over-supplementation can cause zinc toxicity very easily. 

Calcium & Phosphorous — These two minerals are grouped together because they have to be in balance from both sides otherwise your chickens will suffer from rickets or caged layer fatigue. A chicken’s diet must have twice as much calcium as inorganic phosphorous; if it wavers from this 2:1 ratio then signs of a deficiency form. These signs in a young chicken are the same as that of vitamin D3 deficiency because D3 helps regulate the calcium and phosphorous in the blood. Bowed legs from lack of proper skeletal calcification are the most obvious sign. In laying hens, the eggshells suffer and are often thin or soft. As the hen utilizes the calcium in her bones to form eggshells, she develops osteoporosis until ultimately her legs can no longer support her weight. (Leeson, Mineral Deficiencies in Poultry, 2015) 

While a deficiency in calcium (or phosphorous) can cause rickets in growing chicks, you must still be careful that they do not intake excessive amounts of calcium above 1% weight of their feed. Layer feed typically has 4% calcium by weight. Calcium and phosphorous are very important for growing bones, but too much can also deform bones and damage the kidneys. Having supplemental calcium such as oyster shell separate from the normal layer feed allows a chicken to take only what she needs.

Some of the signs of these nutritional deficiencies in chickens are very similar, so you must be on the lookout for them. This is not an exhaustive list and only contains deficiencies that are more likely to be seen. Help prevent deficiencies by feeding your chickens a well-balanced diet of commercially-formulated feed. Limit treats, scraps, and other extras to no more than 10% of your chicken’s diet. If a nutritional deficiency still arises, address it quickly with the proper supplementation.


Leeson, S. (2015, May). Mineral Deficiencies in Poultry. Retrieved June 9, 2020, from Merck Veterinary Manual:

Leeson, S. (2015, May). Vitamin Deficiencies in Poultry. Retrieved June 8, 2020, from Merck Veterinary Manual:

Originally published in the Backyard Poultry Special Subscriber 2020 issue Comb to Tail Health and regularly vetted for accuracy.

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