Broiler chickens need a high-protein, energy-dense diet that changes as they grow, typically split into three phases: starter, grower, and finisher. The foundation of most broiler diets is a corn-soybean meal mix, adjusted in protein and energy at each stage to match the bird’s rapid growth rate. Getting these ratios right directly affects weight gain, feed efficiency, and your cost per pound of meat.
The Three Feeding Phases
Broilers grow from hatchling to market weight in roughly six to eight weeks, and their nutritional needs shift significantly during that window. The diet is divided into three phases, each with a different balance of protein and energy.
Starter (days 1 to 14): This is the highest-protein phase. Young chicks need around 23% crude protein to support rapid early growth, with metabolizable energy in the range of 2,800 to 3,000 kcal/kg. Research comparing protein levels from 17% up to 26% found that chicks fed 23% or 26% protein had the best weight gains and feed efficiency, but 23% hit the sweet spot when factoring in feed cost per kilogram of live weight gained.
Grower (days 15 to 28): Protein drops slightly to around 20 to 21%, while energy increases modestly. The birds are building muscle and frame at a fast clip, but their digestive systems are more efficient than in the first two weeks, so they convert feed better at a somewhat lower protein level.
Finisher (days 29 to market): Protein settles around 20% and energy rises to about 3,000 kcal/kg or slightly above. The goal here is efficient weight gain with good meat yield. Overfeeding protein during this phase wastes money without meaningful improvement in growth.
Core Ingredients in a Broiler Diet
The backbone of a standard broiler ration is yellow corn and soybean meal. In a typical grower-to-finisher diet, corn makes up roughly 57% of the formula and soybean meal about 33%. Corn provides the bulk of the energy (starch and some fat), while soybean meal delivers most of the protein. The remaining 5 to 10% consists of added fat (usually soybean oil at around 5.5%), a vitamin-mineral premix, salt, and any feed additives.
If you’re mixing your own feed or choosing a commercial product, the corn-to-soybean ratio is what primarily determines whether the diet meets your protein and energy targets. Higher soybean meal inclusion raises protein; more corn or added oil raises energy. Some producers substitute part of the corn with wheat, sorghum, or barley depending on local availability and price, but the nutritional math has to balance out the same way.
Amino Acids That Matter Most
Protein percentage alone doesn’t tell the whole story. Broilers need specific amino acids, and two are consistently the first to fall short in a corn-soy diet: lysine and methionine. Lysine is the primary driver of muscle growth, and methionine (along with cysteine) supports feathering, immune function, and overall metabolism.
During the starter phase, research on young chicks found optimal performance at about 0.74% digestible lysine and 0.58% digestible methionine-plus-cysteine in the diet. The ideal ratio between these two sits around 74 parts methionine-plus-cysteine to every 100 parts lysine. Most commercial broiler feeds include synthetic methionine and sometimes lysine supplements to hit these targets, since soybean meal alone doesn’t provide enough methionine relative to the bird’s needs.
If you’re buying pre-mixed commercial feed, these amino acid levels are already built in. If you’re formulating your own rations, getting the lysine and methionine balance right matters more than simply hitting a crude protein number.
Calcium, Phosphorus, and Bone Health
Strong, fast-growing birds need the right calcium-to-phosphorus ratio to build solid bones and avoid leg problems. For broilers between 21 and 28 days old, research puts the optimal digestible calcium at about 0.70% and digestible phosphorus at 0.55%, giving a calcium-to-phosphorus ratio of roughly 1.26 to 1. By days 28 to 35, phosphorus needs rise slightly relative to calcium, bringing that ratio down to about 1.08 to 1.
Limestone is the most common calcium source in broiler feed. Phosphorus comes partly from the grain and soybean meal, but much of the phosphorus in plant ingredients is locked up in a compound called phytate, which chickens can’t digest well on their own. That’s where enzyme supplements come in.
Phytase and Other Feed Additives
Phytase is an enzyme added to broiler diets specifically to unlock the phosphorus trapped in plant-based ingredients. Without it, a significant portion of the phosphorus in corn and soybean meal passes through the bird unused, which means you’d need to add more inorganic phosphorus (an expensive ingredient) and the manure would contain more phosphorus runoff.
Supplementing phytase at around 4,500 FTU per kilogram of feed has been shown to release roughly 0.15 percentage points of usable phosphorus and 0.165 percentage points of calcium from the existing plant ingredients. At doses of 2,000 FTU/kg and above, phytase also improves amino acid digestibility and energy availability, benefits that go well beyond just phosphorus. It does this by breaking down phytate, which otherwise binds to minerals, proteins, and starches and makes them harder to absorb.
Beyond phytase, many commercial feeds include a coccidiostat (to prevent a common intestinal parasite), a vitamin-mineral premix covering vitamins A, D, E, and B-complex along with trace minerals like zinc, manganese, and selenium, and sometimes a probiotic or organic acid blend to support gut health.
Pellets, Crumbles, or Mash
The physical form of the feed has a surprisingly large effect on broiler performance. Research comparing mash diets to crumble-pellet diets found that birds fed crumbles and pellets had significantly better weight gain and feed conversion. In one trial, broilers on a crumble-pellet diet with 23% protein and 3,200 kcal/kg energy gained 951 grams in the first three weeks with a feed conversion ratio of just 1.31, meaning they needed only 1.31 kg of feed per kg of weight gained.
The practical approach most producers use: crumbles for the first 10 days (small enough for young chicks to eat easily), then pellets from day 10 onward. Mash works in a pinch and costs less to produce since it skips the pelleting step, but birds waste more of it, eat more slowly, and convert it less efficiently. If you’re raising a small backyard flock and buying bagged feed, the crumble-to-pellet transition is usually the best investment you can make in growth rate.
Water: The Overlooked Nutrient
Water intake increases steadily as broilers grow and is just as important as feed formulation. Across two commercial flocks tracked by researchers, cumulative water consumption ran between about 14,000 and 15,300 liters per 1,000 birds over the full grow-out period. That works out to roughly 14 to 15 liters per bird across its lifetime, though daily intake starts small and rises with body weight.
A useful metric is the water-to-body-weight ratio: milliliters of water consumed per kilogram of body weight each day. Tracking this ratio helps you catch problems early, since a sudden drop in water intake often signals illness, equipment failure, or heat stress before you’d notice it from feed consumption alone. Cool, clean water should be available at all times. Dirty or warm water reduces intake, which drags down feed conversion and growth.
Feeding Strategy and Schedule
Most commercial broiler operations use ad libitum feeding, meaning birds have continuous, unrestricted access to feed. This maximizes growth speed, but it comes with trade-offs. Unrestricted feeding drives rapid muscle growth that can lead to meat quality defects, particularly white striping and woody breast, conditions where fat and connective tissue infiltrate the breast muscle.
Intermittent feeding strategies, where birds get brief periods without access to feed, have shown promise in reducing these defects. In one study, birds given short fasting windows starting in the second week of life had visibly less white striping, lower fat content in the breast muscle, and less excess collagen buildup compared to birds fed around the clock. The key finding: these restricted birds caught up in growth by day 42 and showed no significant difference in final body weight, breast muscle weight, or feed conversion compared to the ad libitum group.
For small-scale producers, this means you don’t necessarily need to keep feeders full 24 hours a day. Providing feed for most of the day with a short break (even an hour or two) may improve meat quality without hurting your bottom line. For large operations, the economics of implementing intermittent feeding depend on automation and labor costs, but the meat quality benefits are real.