Bovine immunoglobulins with relation to their activity with in the intestinal tract of the neonatal calf

A study was made of the plasma immunoglobulin levels of 80 neonatal calves under three different forms of management - homebred dairy calves, market calves and sing le suckled beef calves. On assessing the plasma levels of total immunoglobulin by both Zinc Sulphate Turbidity and Refractometer methods, and absolute concentrations of individual immunoglobulins (IgG, IgM, 7S(non secretary) IgA and 11S(secretory) IgA ) by single radial diffusion test, no significant difference was found between homebred dairy calves and market calves. However, the suckler calves had significantly higher plasma immunoglobulin levels than the other two groups, this being attributed to the fact that single suckled beef calves can suckle colostrum at will during the first 24 hours of life. Although calves from all groups scoured, it was very much more severe and of longer duration in the calves with low plasma immunoglobulin levels. Explanations for this finding are discussed, together with methods whereby the plasma immunoglobulin levels of dairy calves might be increased. In addition to the sera from the above calves, sera from 103 market calves were used to establish the value of the refractometer as a simple, rapid method of assessing immunoglobulin levels in neonatal calves. A significant correlation was found between the refractometer readings and the total immunoglobulin content of the serum. Although not quite as accurate as the Zinc Sulphate Turbidity Test, the ( refractometer test was found to be a rapid and useful test under field conditions. Antibody activity to E. coli in bovine serum and colostrum was investigated. IgM was found to represent most of the complete, i.e., haemagglutinating E. coli antibody in both serum and colostrum. IgA was found to have E. coli antibody activity and to be present in much greater amounts in colostrum than in the calves serum, indicating that it may be of more significance in the local intestinal rather than the systemic context and may play an important protective role in the intestinal tract of the newborn calf. A method is described for the preparation of bovine IgA from milk. IgG, IgM and IgA were demonstrated in the serum and faeces of 4 experimental colostrum fed calves. The serum and faeces levels of these immunoglobulin classes were measured for the first 14 days of life and the effects ensuing on these levels from the feeding of colostrum in the absorptive and post absorptive periods noted. By quantitative estimation of IgG, IgM and IgA in neonatal calf serum, faeces and urine, the percentage absorptions of these three immunoglobulins from colostrum were calculated and found to be 89.2% (S.E.=±4.8%), 30.4%( S.E. =±5.2%) and 49.0% (S.E. =±O. 6%) respectively. It was found that the neonatal calf is capable of immunoglobulin production very soon after birth, i.e., it is immunologically competent at birth. IgA administered orally in colostrum appears to take longer to pass through the gastro-intestinal tract than either IgG or IgM. After colostrum feeding, the bulk of unabsorbed IgG and IgM appear in the faeces within 24~48 hours, whereas large amounts of colostral IgA are still being excreted in the faeces up to 6 days later. This delayed excretion of IgA may be of importance to the newborn calf in that the maintenance of a high gastro-intestinal tract level of IgA may neutralise any potentially pathogenic bacteria present. Four colostrum deprived calves were protected against colisepticaemia by the intravenous administration of an IgM rich preparation. 3/4 of these calves developed a fatal enteric infection even though very large a mounts of IgA appeared in the faeces. This faecal IgA which was present even in the calves dying at less than 48 h ours old, must have arisen from active local production by the calves and is presumably stimulated by the enteric infection. The thesis is proposed that IgA plays an important role in the control of enteric colibacillosis in calves in that colostrum fed calves achieve more resistance to enteric infection due to the passive intake of colostral IgA, which fulfills a local protective action in the gastrointestinal tract until the calf's own secretary immune system is established in the intestinal mucosa and capable of producing IgA in sufficient quantities to neutralise any potentially pathogenic enteric bacteria. Finally, during the course of investigating antibodies to E. coli in the faeces, lysis of rbc's, used in haemagglutination antiglobulin tests on faecal extracts from scouring calves, was observed. Since this activity, unlike E .coli α haemolysin was not inactivated by heat, it may indicate that the substance causing haemolysis is host produced rather than a product of bacterial action