Managing leg disorders in broiler chickens

 Lameness in poultry is a very common occurrence, especially with exotic breeds. [File, Standard]

Lameness in the broiler breed of chicken is a fundamental animal welfare issue in the poultry meat industry.

Of the five animal freedom needs, the right to protection against pain, suffering, injury, and disease is key. Economic losses because of lameness are unbearable, starting with the loss of market-age birds, downgrading of chicken meat due to lameness, and the emotional effect on farm workers; seeing birds suffer is unsettling.

Here are the causes of lameness in young growing flocks and how to manage them.

Bacterial infection 

Lameness in poultry is a very common occurrence, especially with exotic breeds. It is mostly associated with bacterial infection due to a microorganism called Staphylococcus aureus. This organism is a normal inhabitant of any poultry unit and is ubiquitous in the environment, existing without causing any problem at all.

Infection occurs when it gets into the birds through the respiratory route; it can also be swallowed with litter and occasionally enter the bloodstream through a cut on the skin or injury during excessive handling of the bird.

Any disruption of the internal lining of the gut may also open a route for this organism into the bloodstream. This occurs after gut infestations with coccidiosis, roundworm invasions, and nonspecific nutritional diarrhoea.

Once in the bloodstream, the organism targets the joints, which are hidden away from immune defence systems, multiplying and causing inflammation (arthritis).

Common clinical signs include swollen joints and the inability of the birds to walk and reach for feed and water.

The remedy is to isolate sick birds and administer appropriate antibiotics in consultation with your vet. Any stressors that will cause litter eating should be avoided.

Ensure there is no inadequate feed allocation, feed restrictions, poor feed distribution, or inadequate feeding equipment. These factors can all result in a frantic fight among the peers, with the weak resorting to litter eating for satiety purposes.

Another bacterial infection commonly associated with lameness is E coli; however, this presents secondary to underlying conditions like coccidiosis, a viral disease like infectious bronchitis. A vet must be involved at this stage for a thorough postmortem and possibly laboratory analysis and isolation of the offending organism.

Other non-infectious causes 

Some multivitamin and mineral deficiencies and toxic insults on the skeletal appendages of a chicken during the growing process can also cause lameness in broiler chickens.

Between weeks three and six, broiler growth rates peak, gaining weight rapidly, often doubling in size with each week. This is the time when any deficiency will result in a severe manifestation of lameness.

As millers move away from animal-based feed to a 100 per cent grain-based diet, there are increases in calcium and phosphorus deficiencies.

Calcium is an important component of bones, and since a grain-based diet is generally low in calcium, this must be supplemented as ground limestone (calcium carbonate); otherwise, the presented picture is lameness, inability to walk, and soft bones, a condition referred to as rickets.

Vitamin B deficiency causes lameness, toes become curled, and the chicks fail to walk. Vitamin B supplementation in drinking water results in quick recovery. Vitamin D deficiency indirectly results in rickets due to failure to absorb calcium from the gut, with affected birds exhibiting soft beaks and bones and an inability to stand; in extreme cases, you will see a twisted keel or sternal bone.

Prevention of leg health issues

For bacterial infections, prevention relies on controlling the sources of infections and ensuring drinking water is sanitised with chlorine twice per week, always maintaining 2-3  parts per million (ppm).

For Mycoplasma and reovirus-associated infections, ensure you buy your flocks from well-immunised parents against these two infections. The litter must be maintained dry and friable through good ventilation. The diet should be adequately balanced on the calcium-phosphorus ratio, and all essential vitamins are supplemented. Finally, ensure stressors are minimised, provide adequate feed, feeder space, and adequate distribution.

-Dr Messo is the company veterinarian, Kenchic