Medicated or Plain Starter Feed: Which to Use and When

What coccidiosis does to the gut

Coccidiosis is caused by tiny parasites called Eimeria that live in the gut. They multiply in the lining of the intestine and break it down, so the bird cannot absorb her feed properly. A chick with a bad case looks dull, sits fluffed up, and passes blood or dark, watery droppings. Birds that survive often grow slowly and never fully catch up.

The parasite spreads through droppings. Wet litter, crowded houses and dirty drinkers keep the oocysts alive and passing from bird to bird. That is why coccidiosis tends to show up in broilers somewhere around three to six weeks, when the litter has had time to get damp and the birds are eating more.

No single bag of feed decides whether your flock gets coccidiosis. Litter and hygiene do most of that work. The feed is one of the tools you use to manage them, and it should be chosen with the house in mind. The disease itself is described in coccidiosis in chickens, and the gut problems that often follow it are in necrotic enteritis in chickens.

What plain starter relies on

Plain starter is ordinary chick feed with no coccidiostat in it. It is the normal choice when the chicks have been vaccinated at the hatchery, the house is clean and the litter stays dry. Under those conditions the vaccine does the work of building immunity, and the feed does not need to add a drug to the mix.

Plain starter is also the honest choice when you do not yet know your house. The first flock tells you what the litter does, how the drinkers hold up, and whether the floor stays dry after rain. Start plain, look at the droppings and the litter every morning, and let the birds show you where the risk sits.

What medicated starter adds, and why

Medicated starter contains a coccidiostat, a substance that stops the parasite multiplying in the gut. It is preventive. Farmers use it when a flock is at known risk: a house with a history of coccidiosis, a damp floor, a dense flock, or chicks that have not been vaccinated. Giving medicated feed to birds that are already bloody and drooping is treatment, and that is a vet's decision that goes well beyond changing the bag.

The drug also works against the exposure that builds natural immunity. That is the trade-off. Medicated feed buys protection now, and the cost is that the flock may not learn to live with the parasite the way a vaccinated flock does. Whether that matters depends on how long the birds stay on the farm and what happens to them afterwards.

The clash with vaccinated chicks

Here is the part people miss. Coccidiosis vaccines for chicks are generally live products, which means they carry a controlled dose of the same parasite. Our chicks get their coccidiosis vaccine at the hatchery, and the batch record we send with them shows that it was given. Ask us if anything on it is unclear. An anticoccidial in the feed is designed to kill that parasite. Used together without thought, the feed can kill the vaccine before it does its job, and the chicks end up with neither the vaccine's protection nor the feed's.

So the sequence matters. Some vaccine programmes are designed for a particular feeding plan, and some time the medicated feed to start only after the vaccine has taken hold. Ask your vet which programme your chicks are on before you switch to medicated feed. The batch record that comes with your chicks lists what was given at the hatchery, so keep it on the farm and show it to the vet on the first visit. The vaccines themselves, and the timing of any booster, are set out in chick vaccination: what is done and what is next, and the wider calendar is in our poultry vaccination schedule.

Withdrawal periods and the market date

Every medicated feed label gives a withdrawal period: the number of days that must pass between the last medicated feed and the day the bird is sold or slaughtered. The reason is simple. The drug must clear the bird before anyone eats it. Some farms forget this. They switch feeds in the last week and then sell birds that are not ready, and the result can be a rejected batch and a buyer who does not come back.

Work backwards from the market date. Find the withdrawal period on the label, and make sure the last medicated bag comes out of the bin that many days before the birds leave. Our rule is to write the withdrawal date on the feed bin the day the medicated bag is opened. Read the label yourself, and confirm the period with your vet for the exact product you bought, because products differ. For the wider rules on antibiotics and coccidiostats, see responsible antibiotic use and withdrawal.

Which feed for which flock

Use this table as a starting point, then check each row with your vet, because the right answer depends on the house, the vaccine and the history of the site.

Switching between medicated and plain feed

Switch the way you would switch any feed. Change the bag over several days, adding a little more of the new feed each day, so the birds do not drop their intake. A sudden change of feed also upsets the gut flora, and a sensitive chick can go off feed for a day or two, which is the last thing a young flock needs.

When you move from medicated to plain, time the switch to the grower schedule rather than to the day a bird looks big enough to sell. Keep the medicated bag in its dry place until the flock has finished it, and check the label for any mixing advice before you combine it with other feed. Broilers move through starter, grower and finisher phases, and the sequence is laid out in starter, grower and finisher feeds explained.

Mistakes with medicated feed

• Using medicated starter as a cure after the birds are already sick, instead of calling the vet.
• Mixing medicated feed into plain feed to make a bag last, which changes what the birds get in a way nobody can measure.
• Giving medicated feed to vaccinated chicks without asking the vet first.
• Selling birds inside the withdrawal period because nobody wrote the date down.
• Buying a cheap feed with an unclear label, and not knowing whether it contains a coccidiostat at all.

The last one catches more people than you would think. A feed with no clear medication statement on the bag is not a plain feed you can rely on until the supplier confirms it in writing. If you are comparing the additives that sit in feeds like these, feed additives for poultry explained sets out what each one does and when it earns its place.

Keeping the records straight

A feed record and a vaccine record should live in the same folder. For each house, note the feed name, the start date, the date you switched, and the withdrawal date if the feed was medicated. Add the batch record from the hatchery and the dates of any vaccines given on the farm. When the vet asks what the chicks have had, you answer from paper, not from memory.

A simple sheet on the wall works. One column for the date, one for the feed, one for deaths, and one for anything unusual in the droppings or behaviour. If coccidiosis signs come back later, the sheet shows what changed in the weeks before, and that is often where the answer is.

Checklist before you choose a starter

1. Read the batch record and confirm the coccidiosis vaccination.
2. Look at the house floor. Is the litter still dry and loose after the first week?
3. Ask your vet which feed programme fits these chicks and this house.
4. Write the withdrawal period on the bin before you open a medicated bag.
5. Plan any switch over four to five days, not one. Questions about the chicks themselves are answered on our FAQ page.
6. Check the droppings every morning for the first three weeks.

If you are starting a fresh batch, our broiler day-old chicks page sets out what arrives in the box, and you can place an order through the order form. For the early days of a chick's life, see chick starter feed: what and how much.

Questions farmers ask