Calf diarrhoea is a commonly reported disease in young animals and still a major cause of productivity and economic loss to cattle producers worldwide in both beef and dairy cattle herds. Moreover, neonatal calf diarrhoea (NCD) creates a problem in terms of animal welfare and farmer distress.
Diarrhoea in calves has a multifactorial aetiology, in which viruses, bacteria, protozoa and management factors (housing, feeding, hygienic conditions) play a role.
Prevention and control strategies for calf diarrhoea involve multiple factors such as peripartum calving management, calf immunity and environmental stress and contamination. The four major enteric pathogens causing NCD are:
- Bovine rotavirus
- Bovine coronavirus
- Escherichia coli
- Cryptosporidium parvum
Due to the structure of the bovine placenta, the calf is born agammaglobulinaemic and therefore depends on the successful passive transfer of maternal antibodies (Ig) from colostrum. The absorption of maternal Ig across the small intestine during the first 24 hours after birth, termed passive transfer, helps to protect the calf against common disease organisms until its own immature immune system becomes functional.
Multiple studies have shown that failure of passive transfer, as reflected by low serum Ig concentrations (IgG < 10 mg/ml), markedly increase morbidity and mortality in dairy and in beef calves.
The results of some studies demonstrate that even with optimal dam vaccination and a proper colostrum intake, the natural challenge with infectious agents associated with neonatal diarrhoea may overcome the passive immunity conferred by maternal antibodies as well as the neonatal primary immune response. Oral administration of specific antibodies is an attractive approach to establish protective immunity against gastrointestinal pathogens in humans and animals.
Passive immunisation strategy with chicken egg yolk immunoglobulin, referred to as immunoglobulin Y (IgY) provides an efficacious alternative to prevent and control NCD. It has a large number of advantages compared with treatment with mammalian IgG, including cost-effectiveness, convenience and high yield.
Laying hens are very good producers of specific antibodies. After immunisation, the specific antibodies are transported to the egg yolk which can then be purified. A laying hen produces more than 100 mg of yolk antibodies (IgY) per egg. IgY also have biochemical properties that make them attractive for oral immunotherapy: they neither activate mammalian complement nor interact with mammalian Fc receptors that could mediate inflammatory response in the gastrointestinal tract.
Oral administration of specific IgY antibody has been shown to be effective against a variety of intestinal pathogens such as bovine rotaviruses, enterotoxigenic Escherichia coli, bovine coronavirus and Salmonella spp.
Treatment based on IgY modulates the mucosal immune response in the gut towards higher numbers of antibody-secreting cells present in the duodenum and ileum of treated animals. This may represent higher immune surveillance in the gut mucosa, which is one of the main sites of infection of pathogens during the first weeks of life in calves.
The results of a recent study indicate that feeding immunised egg proteins to calves in the first 14 days of life improves growth performance and concentrate intake.
Passive immunisation by oral administration of IgY has been shown to be effective to complement current preventative strategies against NCD.