Dear Dr Messo
I am a regular reader of your articles in Smart Harvest every Saturday. My chicks have an infection I don’t understand. They start by limping, the legs gradually become weak, they lose appetite, and after two to three weeks, they die. The first one to die was 2.5 months old. I have one which is three months old. This one is going down at a high rate. It started to limp on Friday last week, its appetite is down and it can’t move. My neighbour has lost two the same way. Kindly advise. [Susan Wambui, Naromoru]
Thank you for raising this important issue of lameness in growing flocks. It is one of the fundamental animal welfare issues being looked at. Of the five animal needs, the right to protection against pain, suffering, injury and disease stands out. Economic losses as a result of lameness are difficult to bear, as is the loss of market-age birds, downgrading of chicken meat due to lameness and the emotional effect on poultrymen seeing birds suffering. Here are the causes of lameness in a young growing flock and how to manage them.
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1. Bacterial infection
Lameness in poultry is a common occurrence, especially with exotic breeds. It is associated in most cases with bacterial infection due to micro-organism 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. It gets into the birds through the respiratory route, it can also be swallowed with litter and occasionally enters the bloodstream through a cut on the skin or injury during excessive handling of the bird.
Any disruption on the internal lining of the gut may also open a route for this organism into the bloodstream. Things like coccidiosis, roundworm infestations, nutritional diarrhoea may aid in the rapid spread of infection. Once in the bloodstream, the organism targets the joints that are hidden away from immune defence systems, multiplies and causes arthritis and synovitis. Any stressors that will cause litter eating should be avoided. These include low feed allocation, feed restrictions, poor feed distribution and inadequate feeding equipment, which can all result into a frantic fight among the birds, with the weak resorting to litter eating for satiety purposes.
Another bacterial infection commonly associated with lameness is E. coli. However, this presents as secondary to underlying conditions like coccidiosis, a viral disease like infectious bronchitis. It is important that a vet is involved at this stage for thorough postmortem and possibly laboratory analysis and isolation of the offending organism.
2. Non-infectious causes
These include deficiency and toxic insults on the skeletal appendages of a chicken during the growing process. The main effects are seen during the fastest growth period of a bird, which is between the first and fifth week. As millers move away from animal-based feed to a 100 per cent grain-based diet, we have seen increases in calcium deficiency. Calcium is an important component of bones and since a grain-based diet is low in calcium, this must be added as ground limestone (calcium carbonate), otherwise, the presented picture is lameness, inability to walk and soft bones. In Vitamin B deficiency, where birds are lame, toes are culled, they cannot walk and is very evident in one to two-week-old chicks. Vitamin B supplementation in drinking water results in quick and rapid recovery. Vitamin D deficiency results in rickets, with affected birds exhibiting soft beaks and bones, an inability to stand and in extreme cases you will see a twisted keel or sternal bone.
3. Other causes
These are rare but include diseases like mycoplasma, Marek’s and reoviruses.
Prevention of leg health issues
For bacterial infections, control the sources of infections, ensure drinking water is sanitised with chlorine twice a week, maintaining 2-3 ppm at all times, deworm regularly using appropriate de-wormers, and treat birds against coccidiosis. The litter must be kept dry and friable through good ventilation. The diet should be adequately balanced on the calcium-phosphorus ratio, and all essential vitamins supplemented. Finally, ensure stressors are minimised, and provide adequate feed, feed space and distribution.