Virtually every dairyman will tell you that the success of his operation is dependent on producing healthy, productive replacements. The nutrition and health management of newborn calves is a constant topic of concern, and every producer is looking for a cost-effective, magic combination of products and practices that result in healthy calves on a consistent basis.
With this goal in mind, the industry finds itself in a position where there are as many calf programs out there as there are dairies. This article will focus on an option available to the dairyman as a component of a successful calf nutrition and health program – the feeding of egg antibodies.
The calf is born with essentially no functional immune system. The placental-uterine connection (epitheliochorial placenta) prevents the transmission of immunoglobulins (antibodies) from the cow to the fetus.
Immunoglobulins (Igs) are functionally specific proteins produced by plasma cells and lymphocytes in response to specific antigens. These molecules play an essential role in the body’s immune system.
They attach to foreign substances, such as bacteria, and assist in destroying them, thus preventing disease or reducing the effects.
Immunoglobulins have different structures and functions. They are abbreviated and classified based on this structure. Of these Igs, IgG, IgM and IgA are found in colostrum and are important to the new calf.
Of these, IgGs are particularly important. The IgGs are a class of immunoglobulins found in all body fluids. They are the smallest but most common antibodies (75 percent to 80 percent) in the body.
IgG antibodies are very important in fighting bacterial and viral infections. As such, IgGs are critically important to the function of the developing immune system in the newborn calf.
The primary delivery of maternal antibodies to the newborn calf is via colostrum. The consumption of colostrum by the calf is critical to initiating the development of its immune system and provides an initial passive immunity.
In many cases, consumption of colostrum is insufficient to meet the needs of the calf. The colostrum quality may be poor due to an improperly balanced nutritional program or inadequate vaccination protocols for the cow during pregnancy or after dry-off.
The calf may be born under challenging environmental conditions, poor hygiene or other conditions that are stressful or that create conditions where invading pathogens are in very high concentrations.
Failure of passive transfer of maternal Igs occurs in a high percentage of calves in the U.S. and other countries, due to the way colostrum feeding is managed on dairy farms.
The correlation with mortality is very strong. The USDA has estimated mortality rates related to severe scouring as high as 25 percent. This death loss, along with morbidity, represents a serious economic loss to dairy farmers.
Even with intake of adequate levels of quality colostrum, a gap exists between the coverage provided by the cow’s immune system immediately after birth and when the passive immunity begins post-colostrum consumption.
A second “lag” occurs at 4 to 7 weeks old when the protection afforded by the passive immunity declines and before the calf’s active immune system has built up. This results in pre-weaning sickness of 50 percent or more and average calf death losses of 5 to 8 percent.
Most of these losses are closely related to moderate to excessive scouring in the calf as caused by infection and inflammation of intestinal tissues by various pathogens such as coronavirus, e. coli, rotavirus, cryptosporidia, salmonella and clostridia.
These organisms commonly target the intestinal cells for colonization and attack. A very large part of the animal’s immune system is found within the digestive tract, particularly at the lining of the intestine.
At birth and the weeks thereafter, the immune system in the digestive tract is likely unprepared for the onslaught of organisms that can create health challenges for the very young calf.
One tool that has gained interest of late is the feeding of dried egg products produced from chickens that have been immunized for specific antigens.
Feeding of eggs to calves in an effort to stimulate their health and development has occurred for years. Back when farms included at least a few of every animal and poultry species, the hens roaming the barnyard were exposed to every pathogen on the farm.
While they would seldom show symptoms, these birds would produce antibodies against these pathogens. Chickens only have one opportunity to pass critical antibodies on to their chicks and must do so through the egg. Farmers would mix eggs or egg yolks in with milk or milk replacer to feed to young calves needing a “boost.”
Today, this practice has become much more technologically advanced. Flocks of chickens are immunized with specific antigens in order to stimulate the hens to produce specific antibodies (IgY) against the pathogens that may normally cause intestinal tissue inflammation and diarrhea in the young calf.
After the chickens lay, the eggs are collected, broken, pasteurized and spray-dried into a powder for ease of feeding in milk, milk replacer or calf starters.
During the process, the manufacturer also employs repeated quality control and assurance processes to ensure purity and the measurement of target antibody levels. This dried egg powder is a highly concentrated source of the antibodies.
There are a number of companies which produce these products. One differentiating factor is how a given manufacturer immunizes its flocks. In some situations, the flock is vaccinated with one specific antigen, thus producing a given, specific antibody in the eggs produced by that flock.
This same company will maintain numerous flocks of birds, each immunized for specific antigens. Once the dried egg products are produced, they can be blended together to produce a final product that will provide protection to calves for the various pathogens of concern.
Other companies will immunize a given flock with multiple antigens, thus inducing a single flock to produce multiple antibodies. It has been suggested that this is a less-efficient method and that the resulting antibody concentrations are lower than when birds are immunized for a single antigen.
At birth, calves can be fed low levels (1 to 3 grams) of these egg products to introduce these antibodies to the calf in combination with the colostrum in order to begin building a defense system against many common pathogens.
The dried eggs can be fed continuously to calves for the coming weeks to give the animal time to build its active immune system.
The antibodies from the eggs work at the epithelial level of the calf’s intestine in several ways. They identify and bind specific pathogenic bacteria, rendering them inactive. They also “bundle” these bound, inactivated bacteria together (agglutination) for secretion via feces.
They recognize the processes of specific viruses so these viruses are neutralized and cannot enter the cells. A critical factor in the effectiveness in the egg antibodies is the affinity the antibody has for the specific antigen.
This is related to overall quality of the product and production process. A product showing a high affinity is effective at lower feeding rates. A second factor is avidity.
Avidity is the combined strength of multiple bond interactions between antibodies and antigens. This is more of a quantitative measurement but gives an indication of how well the antibody binds with the pathogen.
The effectiveness of feeding eggs and egg antibodies has been researched for years. Researchers in 1997 reported on a study where colostrum-deprived calves were divided into six treatment groups and challenged with bovine coronavirus.
The groups included non-treated controls, two groups of calves fed egg yolks from chickens hyper-immunized with bovine coronavirus (low-antibody and high-antibody titer levels) and two groups of calves fed colostrum powder of increasing antibody titer from cows vaccinated against coronavirus (low-antibody and high-antibody titer levels).
Control calves showed severe clinical signs and 100 percent mortality by day six of the study. Both titer groups in egg yolk and colostral powder treatments showed statistically significant improvements in health and growth performance compared to control calves.
Animals in the high-titer groups fed either egg yolk proteins or colostrum powder performed the best, with no mortality, lower clinical symptoms and positive weight gain in the face of severe challenge. The high-titer egg yolk group slightly outperformed the high-titer colostrum powder group.
Similar results have been noted in calf challenge studies with e. coli K99 and bovine rotavirus. Challenge studies in mice fed hyperimmunized egg yolk antibodies against cryptosporidium parvum oocysts have resulted in statistically significant reduction of oocyst shedding versus controls.
These along with a variety of similar studies have shown that the use of dried egg products including specific antibodies can be an effective component in a well-designed calf management program.
As mentioned, there are a number of these types of dried egg products on the market, several of which contain egg proteins targeting multiple scour-producing pathogens.
Be aware that for regulatory reasons, unless specific USDA approval studies have been done for specific pathogens, companies are unable to make claims of efficacy against specific pathogens on the label packaging.
Companies are able to provide information on the spectrum of immunization against specific pathogens in their flocks that supply egg yolk powder for their products.
Contact your nutritionist, vet or feed or animal health supplier for more information about dried egg products for use in calf programs. PD
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