At 12 weeks old, chickens should be eating a grower feed (sometimes labeled “starter/grower”) with 16 to 18 percent protein. This is the single most important thing to get right at this age. Your birds are in the middle of their adolescent growth phase, building muscle, feathers, and bone, and a complete grower feed gives them everything they need without the risks that come from switching to layer feed too early.
Why Grower Feed, Not Layer Feed
It’s tempting to jump ahead to layer feed, especially if you’re eager for eggs. But layer feed is formulated with high calcium levels designed for hens that are actively producing eggshells. At 12 weeks, your pullets’ kidneys are still developing, and that extra calcium can cause permanent kidney damage, reduce their lifetime egg production, and shorten their lifespan. The general rule is to wait until 18 weeks, or until you see the first egg, whichever comes first.
If you have a mixed flock with older laying hens and younger pullets, the safest approach is to feed everyone the grower feed and offer oyster shell in a separate dish. The laying hens will eat the calcium they need, and the younger birds will ignore it.
What Grower Feed Looks Like
Grower feed typically comes in crumble or pellet form. Crumbles are smaller and easier for younger birds to eat, while pellets reduce waste since chickens can’t sift through them as easily. By 12 weeks, most chickens handle pellets just fine, but either form works. Look for a bag labeled “grower” or “starter/grower” from any major poultry feed brand. The protein content should be between 16 and 18 percent, which you’ll find on the tag.
Keep feed available at all times. Chickens are grazers, not meal eaters, and restricting access to feed at this age can stunt growth. A standard feeder that stays dry and clean is all you need.
The 90/10 Rule for Treats
Treats are fine for 12-week-old chickens, but they should make up no more than 10 percent of the total diet. Think of kitchen scraps and scratch grains the way Purina’s nutritionists describe them: they’re candy for birds. Fun to eat, but you don’t want them making a meal of it. Too many treats dilute the balanced nutrition in the grower feed, which can slow growth and lead to deficiencies during a critical development window.
Good treats at this age include leafy greens (lettuce, kale, cabbage), watermelon, berries, cooked rice, scrambled eggs, and mealworms. Mealworms are a particular favorite and add extra protein. Scratch grains like cracked corn are popular but are mostly carbohydrates, so keep portions small.
Foods That Are Dangerous or Toxic
Some common kitchen foods are genuinely dangerous for chickens at any age:
- Avocados contain persin, a toxin that can cause heart failure.
- Dried, raw beans contain a compound called hemagglutinin that is toxic even in small amounts. Cooked beans are safe.
- Onions in large quantities destroy red blood cells, causing anemia that can be fatal.
- Nightshade plant parts like green potato skins, tomato leaves, and eggplant leaves contain solanine. Ripe tomato flesh is fine, but the green parts of the plant are not.
- Apple seeds contain cyanide. The flesh is safe, but core apples before tossing them to the flock.
- Chocolate contains theobromine, which is toxic to chickens just as it is to dogs.
- Moldy food of any kind can cause serious illness. If you wouldn’t eat it, don’t give it to your birds.
- Very salty foods like chips or processed snacks can cause salt poisoning, since chickens don’t naturally handle much sodium.
If your chickens free-range in the yard, also watch for toxic plants including foxglove, rhododendron, yew, lily of the valley, and nightshade. Chickens usually avoid plants that taste bitter, but young birds are more curious and less cautious than adults.
Grit: When and What Kind
Chickens don’t have teeth. They grind food in their gizzard using small stones, and they need access to insoluble grit (small, hard pieces of granite or coarse sand) to digest anything beyond their commercial feed. If your 12-week-olds eat treats, scratch grains, grass, or bugs, they need grit available.
Birds that free-range on dirt or gravel usually pick up enough natural grit on their own. If your chickens are on concrete, in a coop, or on soft bedding, offer a small dish of poultry grit free-choice. They’ll take what they need. At this age, use “grower” sized grit, not the larger pieces sold for adult birds.
One important distinction: grit is not the same thing as oyster shell. Oyster shell provides calcium for eggshell production, and 12-week-old pullets don’t need it. Save the oyster shell for when they start laying.
How Much Water They Need
Water is easy to overlook but matters as much as feed. A rough formula from poultry researchers estimates daily water consumption by multiplying a bird’s age in days by 0.2 ounces. At 84 days old (12 weeks), that works out to roughly 17 ounces per bird per day, or just over two cups. In hot weather, consumption goes up significantly.
Keep water clean and cool. Chickens will avoid dirty water, and dehydration at this age slows growth fast. If you notice your birds panting or holding their wings away from their bodies, they need shade and cooler water. Adding a second waterer in a shaded area during summer is a simple fix that makes a real difference.
Feeding Schedule Through the Coming Weeks
Your 12-week-olds will stay on grower feed for roughly another six weeks. Around 18 weeks, or when you spot the first egg, you’ll transition to layer feed. The switch doesn’t need to be abrupt. Mix the two feeds together over about a week, gradually increasing the proportion of layer feed until that’s all they’re eating. At that point you can also put out a dish of oyster shell for extra calcium.
Between now and then, the routine is straightforward: unlimited grower feed, clean water, a handful of treats for enrichment, and grit if they’re eating anything beyond their pellets. That combination covers everything a 12-week-old chicken needs to grow into a healthy, productive hen.