The functional role of secretory antibody systems in early development of the pig and the calf

Nutrition and immunologyT h e relevance of immunology to nutrition has traditionally been limited to the phenomenon of transmission of maternal immunoglobulins to the foetus and neonate.Investigations of the intestinal absorption of colostral antibodies are usually cited in this context.This mechanism has a limited time span, only a matter of hours in the pig and calf, and there is no further augmentation of circulatory passive immunity.As no other analogy could be drawn between immunoglobulins and nutrients, and passive immunity is an essential require mentmainly of the neonate, investigations usually stop short of enquiring into any further role of antibody systems in nutrition.Antibodies in secretions, particularly antibodies of the IgA class, are now known to play an important part in the protection of mucous epithelial surfaces.From the standpoint of the nutritionist the preservation of functional integrity of the intestinal epithelium is important; therefore, by its contribution in these terms IgA has an indirect role to play in nutrition.Also, the possibility of stimulation and control of this natural immunobiological system holds interesting prospects in modern agriculture.I n the new intensive systems of management the young animal is exposed to increasing risk from gastro-intestinal disorders of bacterial origin.Escherichia coli are preponderant among those enteropathogens which may cause a decline in performance of the young animal, possibly leading to frank disease.T h e results of recent studies using germfree pigs monocontaminated with E. coli show the efFects of bacteria on intestinal absorption (Kenworthy, 1973).I n these animals there is a state of relative malabsorption closely associated with microbial proliferation.T h e germfree animal has virtually no immunoglobulins and antibodies (Porter & Kenworthy, 1970) but the intestinal secretory system develops rapidly within the first 3-4 d of challenge.Kenworthy (1973) reported that in this time period there is a considerable recovery from the disturbance in intestinal function although the infecting organism is present.These observations serve to emphasize the potential contribution of local intestinal antibody systems to health, performance and nutrition in the young animal.From birth onwards the intestinal mucosa is bathed by immunoglobulins which are either maternal in origin or synthesized locally by immunocytes in the lamina propria.As a first step it is important to determine the interrelationship between the declining passive maternal antibodies and the developing mechanisms of active intestinal synthesis which provide continuous protection in early life.