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ELISA Testing: How It Works and Why It’s Important

Aug 03, 2016

By: Kelly Whitcomb

The lab at Alternative Dairy Initiative strives to help farmers produce safe, quality milk while managing healthy, sustainable herds. Though milk samples arrive weekly to screen for varied bacteria, somatic cell counts and antibiotic residue, they rarely utilize a very valuable tool we have available: the ELISA.

ELISA stands for Enzyme-Linked ImmunoSorbent Assay and is used by ADI to test for Pregnancy, Leukosis Virus and Johne’s Disease. The ELISA test detects an antibody in fresh, frozen or preserved milk, which is developed when the cow becomes infected, usually within a three-week period. Both Johne’s Disease and Leukosis Virus have great impact on herd health, milk production, and farmer profitability. By taking notice of these illnesses, we can work to limit exposure and sickness to dairy herds and continue to provide safe, quality products.

Leukosis Virus is found in lymphocytes, or white blood cells, and develops throughout the body via lymph nodes. The immune system suppresses because of this attack on the white blood cells, creating a weaker defense system. Leukosis Virus is transferred from animal to animal through nasal discharge or saliva, blood, milk (colostrum), contaminated equipment, or overcrowding of pens. Once Leukosis Virus infects the animal, they can never get rid of it. Symptoms of Leukosis Virus include decreased milk production, infertility, immobility, gastrointestinal complications, weight loss, and eventually mortality.

Johne’s Disease is a devastating disease found in cattle caused by a chronic bacterial infection. The bacteria are greatly shed in the feces, also contaminating the milk and colostrum, making newborn calves most susceptible for infection. It can also be spread throughout herds via contaminated feed or water supply. Johne’s Disease is identified with widespread enteritis, leading to chronic diarrhea, weight loss, decreased milk production, and ultimately death. Once the animal becomes a shedder of this bacteria, it is known to be infected for life.

Both Leukosis Virus and Johne’s Disease can have drastic negative impact on economics and profitability for farmers. Depending on rate of infection, milk production can decrease significantly. For producers selling breeding stock or embryos, value can drop creating a larger financial burden than milk production alone. For these reasons, it is recommended to test herds for these illnesses and practice good management for prevention; ELISA tests are an efficient, affordable way to do so.

Lastly, ELISA Pregnancy checks are a great tool for farmers to utilize for a number of reasons. They provide accurate results in a timely fashion, they are cost-effective, and they improve efficiency of reproductive programs throughout dairy herds. It is a great alternative to palpation, ultrasound and blood testing because of its accuracy and scientific method. The ELISA performs these checks by measuring pregnancy-associated glycoproteins (PAGs) in order to determine whether or not the animal is pregnant. These PAGs are released from the placenta during pregnancy and are specific to pregnancy. This alone is unique in the sense that other tests may be analyzing chemical indicators, such as progesterone, which are not significant to pregnancy alone.

Moving forward the goal of ADI is to further improve the safety and quality of milk being produced by our farmers. In order to do this, we put emphasis on the issues that threaten this goal and provide a solution to fix the problem. By utilizing our ELISA tests, farmers can rule out Johne’s Disease and Leukosis Virus, improve overall health and management, while also monitoring pregnancy throughout their herd in order to operate more efficiently.

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