Many of the diseases that can cause problems in farmyard poultry are the results of infections by parasites, bacteria or viruses, but there are many other types of problem too. These are generally related to diet or management, and most can be readily prevented.
Here are some of the most common non-infectious health problems that could occur in your flock.
- This condition occurs when the contents of the oviduct are forced out into the abdomen and infection develops.
- It can develop after a blow to the abdomen or after infection.
- Affected birds almost always die.
- Prevention involves minimising the risk of hens bumping their abdomen as they enter nest boxes, and preventing hens being startled e.g. by dogs.
- Occasionally hens can suffer from a prolapsed oviduct.
- In this condition the end of the reproductive tract is pushed inside out and protrudes from the vent (cloaca).
- Often the cause is a very large egg in a young hen, and the prolapse is caused by straining.
- The blood covered mass is usually pecked at by other hens and this will continue until she is killed - or rescued.
- As soon as a prolapse is spotted, gently clean and push the prolapse back, then allow the bird to recover alone in a quiet safe place.
- The condition often recurs, so euthanasia is generally the most sensible option.
- Egg binding occurs when a developing egg become stuck in the oviduct.
- It can be difficult to detect unless hens are observed closely for signs of straining and failure to lay an egg.
- Rubbing lubricating well into the vent can sometimes help.
- By inserting a finger it may be possible to break the egg and very very gently ‘milk’ the fragments of shell out without damaging the lining of the oviduct.
- Egg binding is sometimes a fore-runner to egg peritonitis.
Because of their fossicking habits, free-ranging chickens are very susceptible to poisoning. There are many potential poisons in the environment, including:
- some plants (ragwort, yew, nightshade)
- vermin poison (particularly anticoagulant)
- fertilisers (e.g. organophosphate)
- bacterial toxins (e.g. botulism) and algal poisons (e.g. toxic bloom in stagnant water)
- formalin (in livestock footbaths)
- copper (used in livestock foot baths and sprays for fungi on fruit trees)
- selenium (from top-dressing prills)
- lead in paint on the walls of old sheds
- fungal toxins (mycotoxins) in mouldy grain
- Cannibalism occurs when birds peck at the feathers, toes, heads, and vents of other birds.
- If there is bleeding, this induces further pecking that can lead to the death of the bird.
- Vent pecking occurs often in laying hens
- Young hens, especially if they are overweight, are susceptible to prolapse (the oviduct does not retract after the egg is laid), which induces pecking in the vent area
What causes cannibalism?
- Stress is one factor, especially the stress of over-crowding, over-heating, bright lights and/or sheer boredom.
- Dietary deficiencies such as salt, vitamins, or protein can contribute, also insufficient feed,
- Cannibalism shouldn’t be a problem in well-managed free-range farmyard flocks.
- The wounds can be treated with Gentian violet or Stockholm tar to discourage pecking.
- If possible, injured or cannibalised birds should be removed from the flock for a period of time to allow their wounds to heal.
- Allow the birds more space and ensure that there is good ventilation and that the lights are not too bright.
- Give the hens more to do, like offering several feeds of greens during the day or scattering grain on the ground.
- Putting a rooster in with the hens can help keep the hens in order.
- Reducing the light intensity and/or the duration of light during the day can help prevent cannibalism, but note that the length of daylight exposure should not be reduced for laying hens.
- The use of red lights is also thought to help in some cases.
- When the birds’ feathers grow sparsely, ie when the flock is poorly feathered and there are no feathers on the ground, there may be protein deficiency.
- The diet should be improved to ensure sufficient protein.
- If there is insufficient calcium in the diet of layer hens, their eggs may be thin-shelled, and they themselves may have thin brittle bones.
- Offering oyster-shell grit or sprinkling their feed with horticultural lime flour usually corrects the problem.
- Rickets can occur in young birds due to insufficient vitamin D3, calcium and/or phosphorus.
- Commercial feeds and supplements provide these nutrients, but if they are over-diluted the birds will not get enough.
- Birds can synthesize their own vitamin D to a certain extent, with exposure to sunlight.
Vitamin A deficiency
- Vitamin A deficiency generally shows up in autumn, because birds obtain vitamin A from green feed in the summer and can store it for a short period of time in the liver. Once the green feed is gone, they can become deficient unless they are getting a balanced diet.
- Signs include staggering, thinness, paleness and blindness.
- Blood spots may also be seen in eggs of laying birds.
- Early cases recover when cod liver oil is added to the diet.
There are various types of metabolic disease including:
- ‘sudden death’ syndrome (usually affecting relatively big young male chicks from 1 to 3 weeks old),
- ascites (‘water belly’, accumulation of fluid in the abdomen) contributing factors may include rapid growth, cold temperatures during brooding, high altitudes, excess dietary salt levels, excess dust and ammonia in the hen-house, and/or genetic factors
- crippled legs (twisted legs, abnormal joint angles) and lameness in meat-type birds.
These are most common in modern strains of broilers that have a very rapid growth rate, so they are more likely to occur in big commercial enterprises. But they can occur in back-yard broiler chickens too. Mild feed restriction can help prevent these disorders because it slows the growth rate of young birds.