Bloody Droppings in a Mixed-Age Grower Flock
A farmer has 180 Vanaraja growers at 5 weeks of age. The hatchery says they were vaccinated against Ranikhet disease on day 5 and against infectious bursal disease on day 14; there has been no fowl pox vaccination. Two weeks ago he bought 40 chicks of unknown origin and put them in the same shed. Litter is damp and caked near the waterers. In the last three days, six growers have died. Several birds are pale and ruffled, droppings are blood-tinged and mucoid, and some birds are huddling. A neighbour advised amprolium, which the farmer gave at half the label dose for three days; there has been no improvement. He wants to treat the whole flock and also vaccinate the new chicks immediately.
1. Rank the likely causes of the bloody droppings and deaths, and state what you would check before treating.
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The leading diagnosis is coccidiosis, most likely caecal coccidiosis, because of the age (5 weeks), damp litter, blood-tinged droppings, pale ruffled birds and the introduction of unknown chicks. The second possibility is necrotic enteritis, often triggered after coccidial damage; it can produce dark, mucoid droppings and sudden deaths. Other possibilities to keep in mind are salmonellosis, ulcerative enteritis and, less likely, a viral disease with secondary gut damage.
Before treating, check:
- Post-mortem findings from fresh dead birds - caecal cores and blood in caeca point to coccidiosis; foul-smelling, thin-walled gut with diphtheritic membrane suggests necrotic enteritis. A veterinarian or veterinary assistant should do this.
- Litter and water - wet litter, spillage and dirty drinkers favour coccidiosis.
- Medication history - what amprolium product was used, what concentration, and for how many days? Half-dose for three days is enough to suppress but not clear coccidia, and it selects for resistance.
- Vaccination and chick source - the new chicks may have brought a different coccidial load; mixing ages is a major biosecurity fault.
- Feed quality - mouldy feed or a sudden feed change can cause enteritis.
Do not start three different drugs at once. Confirm the diagnosis, then treat the flock and correct litter and water management together.
2. Give an immediate treatment and litter/water plan, including drug withdrawal and why the neighbour's amprolium may have failed.
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Why the amprolium may have failed
- The dose was half the label rate and the course was only three days. Amprolium is usually given at the label dose for about five days; sub-therapeutic use may suppress signs briefly but not break the cycle.
- The birds may have been re-infected immediately from wet litter. Treating birds while leaving infective oocysts in the litter is a common reason for relapse.
- The problem may not be coccidiosis alone; necrotic enteritis or another enteric disease may need different treatment.
Immediate plan
- Separate the 40 new chicks from the 180 growers. Use separate footwear and equipment, and handle young birds first.
- Remove caked and wet litter, scrape and clean the floor, and rebed with dry paddy husk. Do not merely add dry litter on top of a wet layer.
- Clean and disinfect waterers; provide clean water. Chlorination at 2–5 ppm can help water hygiene, but it does not treat coccidiosis inside the bird.
- Treat with amprolium at the correct label dose for five days, or use another approved anticoccidial under veterinary advice. Support with electrolytes and vitamin K if there is blood loss. Do not use amprolium at the same time as a sulphonamide without advice.
- If necrotic enteritis is confirmed, a veterinarian may prescribe an approved antibiotic; follow the withdrawal period strictly. Eggs or meat from treated birds must not be sold during withdrawal.
- Keep treating birds separated from healthy birds if possible, and record deaths daily.
- Do not vaccinate sick birds now. Vaccination during an outbreak is wasted and may increase stress. Wait until the flock is healthy and then follow the schedule.
Prevention is mainly dry litter, clean water, correct stocking and all-in/all-out management. Coccidiostats in feed are useful only if the dose and feeding period are correct.
3. Design a vaccination and biosecurity plan for this mixed-age flock.
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Biosecurity first
- Stop mixing age groups. The 40 new chicks should have been quarantined for at least 14 days, in a separate shed with separate footwear and equipment.
- Use a footbath at the entrance, keep visitors out, and do not lend feeders or crates to neighbours without cleaning and disinfection.
- Clean water lines and drinkers daily; keep litter dry and remove dead birds promptly by deep burial or burning away from the shed.
- Control rodents and wild birds; store feed on pallets and keep it dry.
- Practise all-in/all-out for the next batch if possible, with cleaning and a rest period between batches.
Vaccination plan
- Do not vaccinate the sick flock during the outbreak. Treat and stabilise first.
- Confirm what the hatchery actually gave. Marek's is given at the hatchery; Ranikhet and infectious bursal disease schedules vary.
- For the healthy growers, follow the local veterinary schedule: a Ranikhet booster at about 4 weeks if the early dose was given, infectious bursal disease according to the hatchery schedule, and fowl pox at 6–8 weeks.
- Use the vaccine cold chain: 2–8°C, protected from light, reconstituted vaccine used within about two hours, and no disinfectant in the drinking water before oral vaccination.
- Vaccinate only healthy birds, in the cool part of the day, and record the vaccine name, batch, date and number vaccinated.
Record-keeping: daily mortality, medication, vaccination, chick source and movements of people and crates. In a mixed-age flock, the most important vaccine is often not a vaccine at all - it is stopping the introduction and spread of infection.