In one study, a group of calves receiving high levels of egg-yolk antibodies got very little diarrhea, had no death losses, and actually gained weight despite being exposed to high amounts of E. coli.
By Travis Thayer, DVM
Calf diarrhea is a costly disease, and it can strike even when calves have had problem-free births and adequate amounts of colostrum. Sometimes, environmental factors such as extreme weather, drastic temperature changes, etc., are to blame. Other times, some type of contamination occurs, whether accidentally from the environment, a carrier animal shedding infectious organisms, or a breakdown of sanitation practices.
General treatment of calf scours involves electrolyte therapy, anti-inflammatory medication such as flunixin meglumine, and, when indicated, antibiotic therapy. In recent years, the industry has been applying more natural products to treat calf scours. One example of this type of approach are products containing specifically targeted egg-yolk proteins fed to calves in milk replacer.
The basic idea is that a flock of chickens is vaccinated against a particular disease (for example, E. coli K99, which causes severe scours in very young calves). Just as cows deposit antibodies into their colostrum for the calf to gain immunity, chickens deposit antibodies into the yolk portion of their eggs for their chicks.
The eggs are then collected, and the yolks are separated out and dried down into a powder. The powder contains high levels of antibodies specific to the disease the chickens were vaccinated for (in this case E. coli), and can then be mixed into milk replacer, providing local protection that is “targeted” against that disease in the calf’s intestinal tract.
Egg-yolk antibodies, called “IgY” in the industry, are very similar in structure to bovine IgG, the antibodies found in colostrum. It is generally recommended that people using these products begin putting the product in the calf’s milk replacer beginning at 24 hours of age and feed daily for the first couple weeks of life, since this is the high risk time for calves to get scours. Since the calf’s gut has already stopped absorbing colostral antibody by this time, the egg-yolk antibodies are not absorbed and act locally to bind the disease-causing organism and stop it from attaching in the gut and causing disease.
So how do we know this works? The use of IgY antibodies fed in milk replacer has been shown to be effective in challenge studies published in scientific journals. In one study, researchers fed one group of calves egg-yolk antibodies in milk replacer, and one group of calves got milk replacer without an antibody (the control group). Then, researchers fed all of the calves high levels of E. coli. By day three, all but one of the control calves that did not receive an antibody had gotten severe diarrhea and died, while the group receiving high levels of egg-yolk antibodies got very little diarrhea, had no animals die, and actually gained weight despite being exposed to high amounts of E. coli. Several other studies have documented this effect for bovine Coronavirus, rotavirus, Cryptosporidium, etc.
Products on the market contain antibodies against multiple bacterial, viral and parasitic organisms (such as Cryptosporidium) that cause calf diarrhea. Due to regulatory restrictions on labeling of these types of products, companies are not allowed to put the word “antibodies” or list specific pathogens on the label or in the ingredient list, so usually the ingredient list will read “egg-yolk powder” or something similar. Most companies are happy to provide information on the specific pathogens targeted during the production of their egg-yolk powder.
In addition, some products on the market also contain beneficial bacteria to help colonize the calf’s intestinal tract and “crowd out” the bad bacteria, as well as other natural components that help to maintain gut health. As regulatory agencies are placing more restrictions on antibiotic use in calves, these natural products are beginning to play a bigger and bigger role in raising healthy calves. Consult with your veterinarian or animal health supplier on what products are available and how they might fit into your calf program.
After obtaining a B.S. in Microbiology and a DVM Degree at UC Davis, Dr. Thayer practiced dairy production medicine in California’s Central Valley. He joined AgriLab’s technical services group in June 2005. Contact him at 510-910-3126 or firstname.lastname@example.org.