Stunted Growth in Chickens: Causes, Checks and Practical Fixes

If your chickens are staying small, growing unevenly or falling behind their age mates, do not start by changing feed blindly. Slow growth can come from feed, water, brooding, heat, crowding, disease, parasites, chick quality, genetics or a combination of several problems.

When checking stunted growth in chickens, start with two simple questions: Are all the birds small, or only some of them? And when did the growth begin to slow? Those two answers usually point us in the right direction much faster than guessing.

This guide will help you work through the problem farmer to farmer. If your flock is also panting, huddling, pecking, sitting on wet litter or showing rising mortality, use our Common Chicken Problems guide alongside this one.

What Does Stunted Growth in Chickens Really Mean?

Stunted growth simply means a bird is growing below what is reasonable for its age, breed or strain, production type and management conditions.

The important word there is reasonable. A local chicken, a dual purpose bird and a fast growing commercial broiler should not be expected to weigh the same at the same age. Even among broilers, different strains have different performance targets.

Do not call a chicken “stunted” just because it looks smaller than a picture on social media. Compare the bird with:

• its own flock mates;
• its previous weekly weight;
• the breeder or hatchery performance guide where available;
• feed and water consumption;
• mortality and disease signs; and
• what happened in the flock during the previous one or two weeks.

For commercial broilers, breeder performance charts such as the Ross 308 performance objectives from Aviagen can be useful as a reference. They are targets under good conditions, not a promise that every farm must hit the same number.

How Do You Know Whether Your Chickens Are Really Growing Slowly?

Do not judge growth only with your eyes. Weigh birds.

Take a reasonable sample from different parts of the pen, including some larger, average and smaller birds. Record the average weight and compare it with the previous week and, where appropriate, the target for that strain.

Also look at uniformity. If the average weight looks acceptable but some birds are much smaller than the rest, you still have a problem to investigate.

Ask yourself:

• Are all birds small, or only 10 to 20% of the flock?
• Were they small from arrival, or did they start well and then slow down?
• Is feed intake lower than normal?
• Has water ever finished or stopped flowing?
• Did the weather become very hot?
• Did disease signs or abnormal droppings appear?
• Did growth slow after a feed change?
• Are smaller birds being pushed away from feed or water?

For broilers specifically, our Broiler Growth Problems guide goes deeper into birds that are failing to reach expected market weight.

If All the Chickens Are Small, Check These Things First

1. Feed Intake Before Feed Brand

Farmers often say, “This feed is not working.” Sometimes that is true. But before you condemn the feed, first ask whether the birds are eating enough of it.

Check the quantity offered, quantity left over, feeder space, feeder height, feed wastage and whether feed is reaching every part of the house. A good feed cannot grow a bird that is not eating enough.

Then look at feed quality. A balanced poultry ration must provide enough usable energy, protein, amino acids, vitamins and minerals for the bird’s age and production stage. Poor formulation, damaged ingredients, long storage, mould, wrong phase feeding or excessive substitution of ingredients can reduce performance.

Do not try to fix poor growth by throwing extra protein, lysine, methionine, salt, oil or vitamins into a complete commercial feed without knowing what is actually missing. You can create a new imbalance while trying to solve the first one.

For broilers, compare actual intake and body weight with our Broiler Feeding and Weight Chart.

2. Water Supply

Water problems are easy to underestimate because birds may still have “some” water.

Check whether every drinker is working, whether nipple pressure is adequate, whether tanks run dry during the day, whether water becomes very hot, and whether smaller birds can reach it comfortably.

A bird that drinks poorly will usually eat poorly. Even a temporary water failure can affect feed intake, especially during hot weather.

Do not assume that every borehole or tap source is automatically a growth problem, though. A recent Ghanaian broiler study comparing three local water sources found no meaningful growth difference when the water sources were within acceptable quality ranges. The practical lesson is to test and investigate suspicious water rather than blaming the source by name alone. See the Ghanaian Journal of Animal Science study.

3. Heat Stress

In Nigeria and much of tropical Africa, check heat early when birds are eating less and growth is slowing.

When chickens are too hot, they reduce feed intake and spend more time trying to lose heat. That means less energy goes into growth.

A recent Nigerian study from the Federal University of Agriculture, Abeokuta examined broiler performance under hot conditions and reinforces why heat management matters in our environment. Global research also shows that heat stress can reduce feed intake, body weight gain and feed efficiency.

If birds are panting, holding their wings away from the body, crowding around drinkers or looking worse in the afternoon, use our Heat Stress in Poultry guide.

4. Stocking Pressure and Competition

Overcrowding is not only about floor area. Birds also compete for feeder space, drinker space, cool air and resting room.

Research consistently shows that high stocking pressure can reduce broiler performance, especially when heat is also present. In one controlled study, both heat stress and high stocking density reduced growth performance. You can read the study in Animals.

On the farm, the practical questions are simpler: Can every bird eat? Can every bird drink? Can smaller birds move away from stronger birds? Is air moving through the flock?

Use our Broiler Floor Space guide as a starting point, then adjust for weather, bird size, ventilation and equipment.

5. Brooding Problems in the First Week

A flock can lose growth potential very early.

If chicks were cold, overheated, dehydrated, slow to find feed, crowded badly around the heat source or arrived weak from the hatchery, you may see unevenness later even after management improves.

Look back at your first week records. Did mortality rise? Were chicks huddling? Did they find water quickly? Was the brooder temperature even across the floor? Were some chicks already smaller at placement?

Our High Brooding Mortality guide can help you review what happened during those first days.

If Only Some Chickens Are Small, Think Differently

When the whole flock is small, first check for a flock wide problem such as feed intake, water, heat or management.

When only some birds are small, look more closely at:

• weak or poor quality chicks from placement;
• unequal feeder and drinker access;
• disease or intestinal damage affecting only part of the flock;
• parasites;
• injury or leg problems;
• genetic or sex differences;
• birds that were repeatedly chilled or pushed aside; and
• runting stunting or other enteric disease problems.

Do not simply move all small birds into one pen and assume the problem is solved. Separating weak birds may help them access feed and water, but you still need to find out why they became small in the first place.

Disease Can Slow Growth: But Do Not Diagnose from Size Alone

Many diseases can reduce appetite, damage the intestine or divert nutrients away from growth. But “small bird” is not a diagnosis.

Coccidiosis

Coccidiosis can reduce feed intake, damage the intestinal lining and depress weight gain. A Nigerian experimental study published in the Nigeria Agricultural Journal found that infected broilers had weight gains below the uninfected controls even after feed intake later improved.

If poor growth comes with bloody droppings, diarrhoea, weakness, ruffled feathers or rising mortality, investigate disease promptly rather than assuming the feed is the only problem.

Runting Stunting and Enteric Disease

Some young broiler flocks develop a much wider spread of body weights, poor feathering and persistent small birds because of intestinal disease. The MSD Veterinary Manual describes multicausal enteric disease: also called malabsorption or infectious stunting syndrome: as a condition that can cause permanent runting, poor feathering, undigested feed in droppings and poor feed conversion.

Astrovirus and other enteric viruses can also be associated with runting stunting in young broilers. Diagnosis may require laboratory testing. Do not start treating every small bird for “runting stunting syndrome” simply because it is underweight.

For a broader symptom check, use our Signs of a Sick Chicken guide and the Poultry Diseases and Symptoms in Nigeria pillar.

What About Phytate and Feed Digestibility?

Phytate is a natural compound found in many plant ingredients such as maize, soybean meal and other grains and legumes. It can bind phosphorus and affect the availability of some nutrients.

But the solution is not to search for poultry feed that contains “no phytate.” That is unrealistic with many plant based diets.

Commercial feed formulation may use phytase: an enzyme that helps break down phytate and improve phosphorus use. Whether phytase is required, and at what level, is a formulation decision for the feed manufacturer or nutritionist.

For the farmer, the practical job is simpler: buy feed from a reliable source, store it properly, watch intake and performance, and investigate a feed batch when growth changes suddenly after the feed changes.

Genetics and Breed Matter More Than Many Farmers Realise

Not every chicken is designed to grow at broiler speed.

Nigerian research on improved tropically adapted chicken breeds showed clear performance differences between breeds and locations. That is why it is misleading to compare every bird with one commercial broiler chart. See the Nigeria performance evaluation study.

If you bought day old chicks as a particular commercial strain, use the hatchery or breeder target for that strain. If the birds are crosses, local chickens or dual purpose stock, use a more appropriate benchmark.

A Farmer’s Step by Step Check for Slow Growing Chickens

1. Weigh a sample. Do not rely on appearance alone.
2. Separate “all birds small” from “some birds small.” That changes the investigation.
3. Check feed intake and feeder access. How much did the flock actually consume?
4. Check water delivery. Tanks, lines, nipples, drinkers and access.
5. Review heat and ventilation. Especially afternoon conditions.
6. Check stocking pressure. Floor space is only part of the story.
7. Review the first week. Weak brooding can show up later as uneven growth.
8. Look at droppings and general health. Growth problems can be disease related.
9. Review feed changes. Did the problem begin after a new batch, phase or supplier?
10. Compare with the correct breed target. Not every chicken has the same growth potential.

What Not to Do When Chickens Are Not Growing

• Do not change feed every few days. You make it harder to know what caused the problem.
• Do not add random supplements to a complete ration. More is not always better.
• Do not copy another farm’s drug programme. Poor growth has many causes.
• Do not starve birds to “improve feed conversion.” Restriction affects growth and should not be improvised.
• Do not compare local or dual purpose birds with fast commercial broilers.
• Do not ignore small birds until market age. The earlier you find the reason, the more useful your correction can be.

When Should You Call a Veterinarian or Poultry Professional?

Get qualified help when:

• growth suddenly drops across the flock;
• mortality is increasing;
• birds have diarrhoea, bloody droppings or severe respiratory signs;
• many birds remain very small despite good access to feed and water;
• feed intake is normal but weight gain remains poor;
• you suspect coccidiosis, malabsorption or another intestinal disease;
• the flock is becoming more uneven every week; or
• you have changed the obvious management faults and the flock is still not improving.

Frequently Asked Questions

Can a stunted chicken catch up later?

Sometimes, especially when the cause is corrected early and the bird has not suffered lasting disease or developmental damage. But severely affected birds may never fully catch up with their flock mates.

Does more protein make chickens grow faster?

Not by itself. Chickens need the right balance of energy, amino acids, vitamins, minerals and feed intake for their age. Excess protein cannot correct heat stress, poor water access, disease or overcrowding.

Why are some broilers big and others very small?

Look at chick quality, feeder and drinker access, disease, brooding history and whether weaker birds are being pushed aside. A wide weight spread can also occur with intestinal disease or mixed genetics.

Can heat make broilers stop growing?

Yes. Heat can reduce feed intake and weight gain. If growth drops during hot weather and birds are panting, heat management should be one of your first checks.

Should I separate small chickens from the bigger ones?

It can help smaller birds reach feed and water, especially if competition is obvious. But separation is not a diagnosis. Find the cause of the size difference as well.

Bottom Line

Stunted growth in chickens is not one disease and it does not have one magic treatment. Start with records: body weight, feed intake, water, weather, brooding history and the pattern of affected birds.

If the whole flock is small, investigate flock wide problems first. If only some birds are small, look harder at chick quality, competition, disease and intestinal problems.

The farmer who weighs birds and follows the pattern will usually get closer to the real cause than the farmer who keeps changing feed, vitamins and drugs without a clear reason.

Veterinary disclaimer: This guide provides general poultry management and animal health information. It does not replace flock examination, laboratory diagnosis or treatment by a qualified veterinarian or animal health professional.