John D. Summers

Some nutritional implications of leg problems with poultry

Summary It would appear that while numerous nutritional situations can lead to skeletal problems, treatment of such problems is far from clear. It would seem that ‘induced’ deficiencies are likely the major cause of leg problems that have a nutritional component, and as such nutritionists are urged to avoid nutrient excesses and antagonisms that may precipitate deficiencies. In many instances there is an underlying common effect of irregular vascularization of the cartilage growth plate, and this seems to be related to growth rate per se , rather than body weight. It has been suggested that genetic selection for improved growth rate has resulted in increased growth rate of the proximal growth plate, especially of the tibiotarsus. Improvements in skeletal development will accrue from more detailed studies of the metabolism of this active growth plate. High levels of diet protein aggravate skeletal development by either increasing growth rate per se , providing excess of nonessential nitrogen, or aggravating deficiencies of vitamins. A number of feed ingredients and mycotoxins seem to aggravate leg bone development in the broiler chicken. Electrolyte balance of the diet can also influence occurrence of leg problems, and in particular tibial dyschondroplasia.

A consideration of comparative metabolic aspects of the aetiology of sudden death syndrome and ascites in broilers.

There is some evidence to suggest that the aetiology of Sudden Death Syndrome (SDS) and ascites in broilers are closely related and that they may be the result of different degrees of the same metabolic condition. Many of the clinical findings, such as cardiac involvement and oedema are common to both conditions. Males are more affected than females and rapid growth, if a factor, is more related to increased oxygen demand rather than growth per se. Dietary, environmental or other factors which disrupt the balance of electrolytes, metabolites or pH may affect cardiopulmonary function and lead to SDS or ascites. The conditions can be either acute or chronic in nature and, whereas if acute, the end result is SDS, when chronic, ascites is the end result. Dietary or environmental factors that may either help to stabilize or adversely affect acid base balance may be useful avenues for future research into the aetiology of SDS and ascites. Factors that would increase the birds capacity for supplying adequate oxygen to the tissues may also help to alleviate these two conditions which are of considerable annual cost to the poultry industry.

Canola meal and acid-base balance

Although canola meal is readily accepted in North America as a quality feed ingredient, there are still occasional reports of increased leg problems and reduced performance of birds when canola meal has been substituted for a significant amount of soybean meal protein. Canola meal contains approximately 1.14% sulphur compared with 0.44% in soybean meal. Work reported in the literature demonstrates that increased levels of dietary sulphur can result in reduced bird performance which can be partially alleviated by the addition of calcium. The present report looks further into the question of high dietary sulphur levels in canola meal reducing bird performance due to allocation of dietary acid-base balance.