Although easy to remember, the 4-4-4 rule in colostrum management is often difficult to put into practice. This rule states that the cow should be milked the first four hours after calving and that the calf should be provided with 4 quarts of high-antibody colostrum within four hours after birth.

Scientific explanations backing up that rule are quite simple:

1. Immunoglobulins G (IgG) present in high amounts in mammals’ blood are transferred into the colostrum during its production. However, the concentration of IgG in colostrum varies enormously from animal to animal and also depends on colostrum milking time and on water dilution effects.

2. IgG concentration in colostrum makes up approximately 5 percent of colostrum content immediately postpartum but is significantly reduced with the increased number of postpartum milkings.

3. Soon after birth the capacity of calves’ intestines to absorb IgG is reduced due to the maturation of the epithelial cells. Fifty to 75 percent of this absortion occurs within the first 12 hours and, at 24 hours, this capacity is gone. The sterile intestinal tract environment with which the calf is born is soon disrupted by environmental bacteria trying to colonize the gut.

Unlike humans, in whom the blood stream of the fetus is in contact with the maternal blood stream (hemochorial placenta), in ruminants two layers of cells impede this contact (epitheliochorial placenta) and therefore make the transference of immunoglobulins during gestation impossible.

Thus, in ruminant offspring, colostrum represents the sole source of initial acquired immunity.

Despite strenuous efforts to improve calf-care protocols, calf diarrhea (scours) still accounts for more than 56 percent of all pre-weaned heifer mortality. This can be attributed to factors such as inadequate cow vaccination and/or immune response, colostrum quantity or quality, environmental issues, pathogen prevalence or labor.

Therefore, assessing the root cause(s) can prove very difficult even in the best managed dairies. However, new technological advances and product development efforts have emerged during the past few years in order to decrease the incidence and the economic impact of calf scours in dairy herds.

IgY present a similar function to that of IgG, thus having an important role in the secondary immune response and being responsible for binding pathogens (virus, bacteria, parasites). While IgG are present in mammals’ blood, IgY are present in the serum of poultry species.

In fact, nature is well organized and before hens lay an egg, they make sure that single cell – which will be developing for around 21 days before it originates a being – is capable of surviving independently throughout incubation and also in the first days after hatching.

That is why IgY are transferred from the progenitor’s serum into the egg yolk while the egg is still in the ovary. Just like colostrum, eggs also possess smaller amounts of IgM and IgA, which are secreted into the egg white during the passage of the egg through the oviduct.

Practical application
Older generations of dairy farmers, keeping some layers for production of farm eggs for family consumption, sometimes found improvement in scours when raw eggs were added to milk fed to calves.

This habit relies in one very simple scientific fact – hens exposed to pathogens will transfer specific antibodies from the serum to the egg yolk.

Today, it is well known that antigen-specific IgY can be produced on a large scale from eggs laid by chickens immunized with selected antigens.

Moreover, the phylogenetic distance between chickens and mammals renders possible the production of an efficient immune response with a much lower amount of antigen.

Just like IgG, IgY rely on two important characteristics which enable them to recognize a pathogen and attach to it – affinity (specificity) and avidity (the binding strength of the antibodies) – the first emphasis being more on qualitative features and the second being more quantitative.

The interaction between an antibody and an antigen (pathogen) can be visualized as a handshake: There are some people you just do not feel impelled to greet and, among those you do, some will be able to generate a more energetic handshake than others.

The avidity of antibodies obtained from immunized chickens is comparable with or even higher than that of antibodies obtained from cows immunized with the same antigen.

‘4-4-4-IgY’
The USDA estimates that between 4 and 25 percent of all calves die of scours every year. The economic impact of this fact goes beyond mortality alone and raises questions concerning the long-term effects on overall herd health and productivity and the treatment and labor costs generated by these occurrences.

Managing newborn calf health and avoiding scours is a hard job for any dairyman, but the use of IgY in the 4-4-4 equation has been proven to ease this task. Do your research to ensure the product you choose has the demonstrated quality and efficacy to meet your expectations.  PD

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Rodrigues is a technical manager with EW Nutrition.