Birds pertaining rapid growth and heavy body weight, are usually associated with a week skeletal body. This has been implicated in musculoskeletal and cardiovascular disease in meat-type poultry. It does not always necessarily result in disease but many of the complications can be eliminated by slowing down the growth rate and research on this has produced contradictory results. Therefore it would be more correct to be called as metabolic disease, since most of these diseases are due to metabolic imbalances associated with rapid growth.
If the hypothesis that musculoskeletal deformity caused due to rapid growth is valid, then we must take into account how specific defects could be associated with rapid growth.
1) The defect may be due to increase in body weight.
2) The defect could occur because of undeveloped tissues (bones, ligaments, tendons, and muscles). This is because as the strong tissue is produced, remodelling and bone alignment would require more duration than rapid growth.
3) The defect could be related to high amino acid supplement, enzyme, hormone, or oxygen requirement by specialised cells.
4) The defect may be due to metabolic by-products such as carbon dioxide and lactic acid that are increased by rapid growth.
5) Rapidly dividing cells could be more prone to toxic or metabolic injury.
Most of the skeletal deformities in birds result in birds that are not able to walk. Birds in these cases find difficult to get feed and water due to chronic pain and anxiety associated with aggression from other birds.
Skeletal deformities can be caused in a variety of ways. Nutritional deficiencies are one of the causes in skeletal disease in all birds. Birds that are growing fast have higher requirement of essential amino acid supplement and have more skeletal defects than in slower growing strains. Mechanically induced or trauma-associated problems are also much more frequent in fast-growing broilers. These problems may be caused due to immaturity and weight than rapid growth because tissue becomes stronger and more resilient with age. This age-related effect is particularly true of bone, tendon, and ligament. Toxins in feed or water can cause skeletal deformities. Toxin effects are not usually associated with rapid growth, although rapidly growing birds would consume more of the offending product. Genetic problems may also result in skeletal defects, but not related to growth.
To conclude, prevention of musculoskeletal disease in chickens must be the goal, and attempts should be made to find management and nutritional techniques to reduce bone defects such as better lighting programs appear to improve broiler mobility and better methods of catching and transferring birds.