Disease, nutrition–interaction

Practical implications of interactions between disease and vitamins in poultry were sought in the readily available literature. The evidence, almost exclusively in chickens, is in accord with that reported in other animals and man,namely 1) dietary vitamin deficiencies can impair body defense mechanisms against disease and 2) occurrence of disease can increase vitamin requirements. Information on viral infections is inadequate and conflicting. Slight indications exist for positive interactions with ascorbic acid and for antagonistic ones with vitamin A. Studies on bacterial diseases involved 7 organisms, 11 vitamins, and 29 observations of which 25 (86%) indicated positive interactions. Those on parasitic infestations involved 9 organisms, 9 vitamins, and 55 observations of which 34 (82%) indicated interactions. The major evidence for interaction between individual vitamins and disease categories was for vitamin A and ascorbic acid in bacterial infections and for vitamins A and K in parasitic infestations. The numbers of confirming studies on individual diseases and vitamins deemed to be reasonably adequate to demonstrate specific interactions were limited to vitamin A in coccidiosis, in ascariasis, and probably in infectious coryza and of vitamin K in coccidiosis. Despite the paucity of specific and quantitative evidence, it appears likely that vitamin levels in chick rations containing generous margins of safety, as referred, should be adequate to meet the increased requirement caused by most diseases. However, when liver reserves of vitamin A are depleted, notably by severe coccidiosis, the effects may be ameliorated and recovery may be aided by additional vitamin A and possibly other fat-soluble vitamins. Decision for such augmentation, selection of formulation, and mode and duration of administration require collaboration of the pathologist and nutritionist familiar with the particular circumstances. It has not been proven that vitamins exert a pharmacodynamic effect or that they will replace the use of appropriate prophylactic or therapeutic drugs. Multidisciplinary research on specific nutrient requirements as affected by specific disease entities is sorely needed.