A build up of worm eggs on free range paddocks which have been in operation for a number of years can be very significant, and the cycle needs to be broken by good paddock rotation, including resting paddocks for several months before introducing a new flock..
Worm infestations have been thought to be rather seasonal but in temperate parts of Australia, worms present a potential year round problem.
Depending on the type of intestinal worms, the bird's gut can be severely damaged, restricting egg production, causing loss of body weight and death.
Affected hens are at risk of egg peritonitis and secondary gut problems involving bacterial infections. In cases involving many birds in the flock, production can be hit very severely as the hens are unable to utilise all of the nutrients in their feed.. Egg quality is likely to decline, particularly yolk colour with a reduction in egg size as well as loss of shell colour and strength.
There is also an increased risk of vent pecking which may lead to cannibalism.
Three main types of worms cause problems in free range hens. Roundworms and Hairworms affect the duodenum and small intestine, Hetarakis worms affect the caeca.
Roundworms (Ascaridia galli)
These are the largest and most common of the chicken intestinal worms and can completely block the intestines. Worms are white with adults up to 2 inches long which can be easily seen in droppings.
Hairworms are small and just visible. These worms are capable of causing severe damage to the intestine even in small numbers. Hairworm infection can be identified by examining faecal material under the microscope or looking at intestinal material from birds submitted for post mortem.
Caecal worms (Hetarakis gallinarum)
Hetarakis worms spend most of their time in the caeca. The worms themselves often cause no obvious problem but their significance is that they can carry another parasite (Histomonas) into the bird. Histomonas is the cause of Blackhead which can cause deaths in free range flocks.
Chickens become infected with worms by picking up worm eggs from their surroundings. This may be from within the shed or from soil, grass or faecal material on the range. Worm eggs are resistant to disinfectants and the normal cleaning and disinfection programme used in poultry sheds between flocks does not remove all worm eggs. A new flock of pullets may be exposed to worm eggs as soon as they arrive, both in the shed and out on the pasture.
Monitoring bird health is important. You need to be aware of signs of listlessness in the hens and regular inspection of droppings is important. If you suspect a problem, talk to your vet.
Good paddock rotation, with lengthy rest periods between flocks is the most effective worm control program but worming is also important. If you don't want to use chemicals, cider vinegar in the water, access to plants which are vermifuges (for exmple Wormwood or Garlic) and mixing diatomaceous earth in feed can help to control internal worm infestations.
The area closest to a fixed shed is always a high risk area for build up of worms and other pathogens, which is one reason for the populartity of mobile chicken sheds.
The UV rays in sunlight are the best killer of worm eggs.
Understand the worm risk on your farm and include a worm monitoring and control strategy in your animal health plan.
For anyone who wants to see post mortem training videos, have a look at: