Chickens need six categories of nutrients to stay healthy and productive: protein, energy (from carbohydrates and fats), vitamins, minerals, essential fatty acids, and water. The exact amounts shift depending on whether you’re feeding young chicks, growing pullets, laying hens, or meat birds, but the core nutritional building blocks remain the same.
Protein Needs Change With Age
Protein is the nutrient that varies most across a chicken’s life. Young chicks need the highest concentrations because they’re building muscle, feathers, and organs at a rapid pace. As they mature, protein requirements taper off. Here’s how it breaks down:
Meat birds (broilers) need about 23% crude protein in their starter feed from hatch through 3 weeks, dropping to 20% from 3 to 6 weeks, and settling around 18% from 6 to 8 weeks. Pullets being raised for egg production start lower, at 17 to 18% protein for the first 6 weeks, then gradually decrease to 14 to 15% through weeks 12 to 18. As they approach their first egg, protein bumps back up to 16 to 17%.
Adult laying hens typically need 15 to 18% protein in their feed, with brown-egg layers on the higher end. Chickens don’t technically have a fixed “protein requirement” in the way we think of it. What they actually need are amino acids, the building blocks that make up protein. The feed just has to supply enough total protein so the bird can manufacture all the amino acids it can’t get directly from the diet.
Amino Acids: The Real Priority
Two amino acids matter most in poultry nutrition because they’re the ones most likely to be deficient in a grain-based diet. Lysine is considered the reference amino acid, and methionine is the first one to run short. In laying hen diets, methionine should be supplied at roughly 47 to 51% of the lysine level on a digestible basis. When either falls too low, you’ll see reduced growth in young birds and fewer, smaller eggs in layers.
Commercial feeds built on corn and soybean meal naturally provide a decent amino acid profile, which is one reason that combination dominates the poultry feed industry. When formulations substitute other grains, synthetic amino acids are often added to fill the gaps.
Energy From Carbohydrates and Fat
Energy fuels everything a chicken does, from maintaining body temperature to producing eggs. It’s measured as metabolizable energy, and for most chicken feeds, the target falls between 2,700 and 3,000 kilocalories per kilogram of feed. Layer pullets in the starter phase do well at 2,750 to 2,970 kcal/kg, and adult hens in peak production need roughly 2,770 to 2,860 kcal/kg. As hens age past 55 weeks, their energy needs dip slightly to 2,550 to 2,825 kcal/kg.
Grains like corn, wheat, and barley supply most of this energy through carbohydrates. Fats are added to boost the calorie density when needed, since fat contains more than twice the energy per gram as carbohydrates. The total fat content of a layer diet is commonly around 3 to 6%.
Linoleic Acid and Egg Size
Chickens can’t manufacture linoleic acid on their own, making it an essential fatty acid that must come from the diet. Its most visible effect is on egg size. Hens fed diets with less than 0.8% linoleic acid produce noticeably smaller eggs. Bumping that level up to about 1% increases average egg weight, and most feed mill nutritionists recommend at least 1.4% to optimize egg size.
Research on brown-egg layers found that once linoleic acid reached 1.03% in a diet containing adequate total fat (around 6.2%), pushing the level higher to 2.7% didn’t increase egg size any further. So there’s a clear floor below which eggs shrink, but adding more beyond that threshold doesn’t help. Corn oil, soybean oil, and sunflower seeds are common sources of linoleic acid in poultry diets.
Key Vitamins and What Happens Without Them
Chickens require a full spectrum of vitamins, but three deserve special attention because deficiencies show up quickly and cause serious problems.
Vitamin A
This vitamin supports the health of mucous membranes throughout the digestive and respiratory tracts, plus normal vision. Chicks that don’t get enough become drowsy, stop eating, and grow poorly. Their shanks and beaks lose yellow pigment, and their combs turn pale. In adult birds, egg production drops sharply and hatchability declines. A prolonged deficiency causes a cheesy white material to build up in the eyes, eventually destroying vision entirely.
Vitamin D3
Vitamin D3 controls how well a chicken absorbs and uses calcium and phosphorus. Without it, young birds develop rickets (soft, deformed bones), even if their diet contains plenty of calcium. Laying hens on a D3-deficient diet lose egg production within two to three weeks, and shell quality deteriorates almost immediately. Bones become soft and prone to spontaneous fractures, particularly along the ribs. Birds with outdoor access synthesize some D3 from sunlight, but confined flocks depend entirely on their feed.
Vitamin E
Vitamin E acts as an antioxidant, protecting cells from damage. Deficiency can cause a range of neurological and muscular problems. Most commercial feeds include supplemental vitamin E as a standard ingredient.
Calcium, Phosphorus, and Trace Minerals
Calcium is the mineral laying hens consume in the largest quantity. A single eggshell contains about 2 grams of calcium, so hens in production need 3.5 to 4.5% calcium in their diet. Offering oyster shell or crushed limestone as a free-choice supplement lets individual hens take what they need. Growing chicks, by contrast, need far less calcium (around 1%), and too much can damage their kidneys.
Phosphorus works in tandem with calcium for bone health, and the ratio between the two matters as much as the absolute amounts. Vitamin D3 ties the whole system together by regulating absorption of both minerals.
Several trace minerals are required in tiny but critical amounts. Broilers need about 40 parts per million (ppm) of zinc for growth and gut health. Manganese supports bone development and antioxidant function, with supplementation in the range of 25 to 100 ppm showing benefits in research trials. Selenium, needed at just 0.15 to 0.30 ppm, supports immune function and feather health. These trace minerals are typically included in the premix that commercial feed manufacturers add to their formulations.
Salt and Sodium
Chickens need a small amount of sodium chloride (table salt) in their diet for nerve function and fluid balance, but the margin between enough and too much is narrow. The recommended maximum is 1.7% sodium chloride in the total feed, which works out to roughly 0.65% sodium. Going above that level risks salt toxicity, which causes excessive thirst, watery droppings, and in severe cases, death. Some nutritionists suggest keeping sodium even lower, around 0.45%, to build in a safety margin. If you’re mixing your own feed, measure salt carefully rather than estimating.
Water: The Overlooked Nutrient
Chickens drink roughly 1.6 to 2 times as much water as they eat by weight, making water quality and availability more impactful on health than almost any feed ingredient. A flock of 1,000 laying hens at peak production (90% lay rate) drinks about 270 liters per day at a comfortable 21°C (70°F). Broilers at 6 weeks of age consume around 330 liters per 1,000 birds daily.
Heat is the biggest variable. As environmental temperature rises, water intake climbs significantly while feed intake drops. During hot weather, making sure waterers are clean, full, and cool enough to be appealing can prevent the production losses and health problems that come with dehydration. Even brief interruptions in water access reduce egg production faster than the same interruption in feed.