Heat Stress, Wet Litter and an Antibiotic Decision in a Broiler House
A 2,000-bird broiler farm in Angul reports at day 32 that feed intake has fallen 8% and body weight is below target. Water intake has risen sharply, litter is wet, many birds are panting, some are lying on their sides, and mortality is 0.25% per day for three days. The shed is 18 m × 9 m with one ridge vent, no side curtains on the west, and fans that are not working. Outdoor temperature is 39 °C and relative humidity 55%. Placement stocking density was 12 birds/m². The farmer has added extra feeders and waterers but put them near the brooding end, so the far end is crowded. He plans to use a broad-spectrum antibiotic in drinking water and to continue to market at day 38.
1. Calculate the actual floor space per bird and stocking density. Is the main problem likely infectious or environmental? Use the signs and management details to support your judgement.
Read the worked answer
Floor area = 18 × 9 = 162 m².
Stocking density = 2,000 ÷ 162 = 12.35 birds/m².
Floor space per bird = 162 ÷ 2,000 = 0.081 m²/bird, or 810 cm²/bird.
This is tight for heavy 32-day broilers, especially in 39 °C heat. The main problem is environmental, not primarily infectious:
- Panting, lying on the side, sharply increased water intake and wet litter fit heat stress and poor ventilation.
- Fans are not working, the west side has no curtains, and there is only one ridge vent - all reduce air movement.
- Feed intake has fallen, which is typical of heat stress, and body weight is below target.
- Crowding at the far end makes local density even higher than the calculated average.
An antibiotic will not correct heat stress, poor air movement or overcrowding, and it creates residue and resistance risks.
2. List immediate actions for the next 48 hours, in priority order, and explain how each reduces mortality.
Read the worked answer
- Restore air movement - repair fans, open the west and north sides with mesh or curtains, and ensure the ridge vent is open. Moving air increases evaporative heat loss and reduces panting deaths.
- Reduce heat load - whitewash or sprinkle the roof, provide shade, and avoid fogging if it will make the litter wetter. Lower radiant heat and keep birds off hot side walls.
- Spread the birds and resources - move feeders and drinkers to the crowded far end, partition the house if possible, and remove some birds or market a batch if density cannot be reduced. This lowers local competition and heat production.
- Provide cool, clean water - flush lines, shade tanks, and offer electrolytes only under veterinary advice; cool water supports panting birds.
- Manage litter - remove the wettest caked litter, improve drainage, and avoid unnecessary water spillage. Dry litter reduces ammonia and footpad damage.
- Do not start an antibiotic without diagnosis - heat stress is not a bacterial disease. If a veterinarian diagnoses a bacterial infection, use the prescribed drug and observe the withdrawal period.
3. Should the farmer market earlier or continue to day 38? Support with a partial-budget and risk reasoning, including the antibiotic withdrawal issue.
Read the worked answer
Daily mortality at 0.25% of 2,000 = 5 birds/day. At a market value of about ₹120 per bird, that is roughly ₹600/day lost, before the cost of extra feed and the lower weight gain caused by heat stress.
Continuing to day 38 exposes the flock to 6 more days of heat: about 30 more deaths, continued poor feed conversion, wet litter and possible heat-stroke losses. Marketing in batches from day 34–36 at a lower weight reduces this risk, frees shed space, and lowers feed cost. The trade-off is lower sale weight and possibly a lower price per bird.
The antibiotic plan changes the decision. If the farmer uses an antibiotic without a diagnosis, he may face a withdrawal period that forces him to keep birds beyond day 38, increasing heat risk and residue risk. If an antibiotic is legally prescribed, the withdrawal period must be respected and birds cannot be sold early. The better plan is to avoid unnecessary antibiotics, correct ventilation, and sell in batches earlier rather than wait for day 38.