Suresh Neethirajan 2016-05-03 01:57:54
When their cows experience a drop in milk production, dairy farmers are often hindered in their ability to determine the cause. One reason is subclinical ketosis (SCK), which means that the affected cow appears healthy and only becomes observably ill when under stress. When SCK becomes full-blown ketosis, major organs can be affected. Other metabolic diseases can also affect milk production and animal health. Until recently, the only reliable method for detecting these abnormalities involved drawing vials of the cow’s blood, sending the samples off to a lab for diagnosis, and then waiting for the results. The BioNano Laboratory at the University of Guelph has improved this process by placing the diagnosis of animal health in the hands of farmers, saving crucial time in detecting diseases, and thereby allowing earlier treatment. Using a handheld biosensor, a dairy farmer can rapidly detect whether a cow has SCK or other metabolic diseases. The analysis can be conducted in real-time, using a smartphone to access the Internet. This technology allows dairy farmers to rapidly determine the cause of a reduction in milk production, and it allows early detection of diseases that can then be quickly treated, helping the cow return to her normal production level in a shorter time. How the biosensor works By detecting certain enzymes in blood, our newly developed device—called GryphSens—identifies biomarkers that are present in miniscule amounts and that indicate the presence of diseases. The device’s unique electrode composition, a plant enzyme, and the correct amount of electric current were discovered to be the winning combination for the design. Specifically, the biosensor detects minute electrochemical activity in biological fluids that indicate biomarkers for certain irregularities. These biomarkers flag slightly elevated levels of non-esterified fatty acids (NEFA) and a ketone prevalent in cows—hydroxybutyrate (BHBA)—that at higher levels can signal the early onset of ketosis and other metabolic diseases. Dairy farmers are well aware that charting a cow’s NEFA and BHBA levels is the litmus test for the animal’s overall health. Calving is a particularly stressful time for cows. It is a time of negative energy balance (NEB), when the onset of ketosis and other metabolic diseases is most common. Although the levels of NEFA and BHBA are miniscule at first, early detection can reduce complications and allow faster recuperation. Delayed detection can lead to fatty liver, displaced abomasum (twisted stomach), inflammation of the uterus, or a retained placenta. Some challenges to overcome While human medicine offers similar devices for measuring glucose levels for diabetics, cows present a challenge by having eleven major blood groups, compared to the four blood groups in humans. An additional challenge was developing an electrode that can simultaneously detect both NEFA and BHBA under variable metabolic conditions that may include a number of interfering components, which can alter the test results. Disposable screen-printed carbon electrodes were used for their affordability and for their compatibility with handheld and in-line robotic milking devices. Based on previous research, the electrodes were fabricated with redox-active hybrid graphene oxide (GO) material, which has proven very effective in biochemical applications. However, we had to overcome the insulating property of the GO material, which hindered the electrochemical function of the biosensor. A particular enzyme from the soybean plant was integral to solving this problem, and this soybean-based enzyme was layered onto the GO material. This proved to be the defining chemical for detecting NEFA and BHBA, as it had superior and durable redox properties for the critical biomarkers compared to untreated GO electrodes. Specifically, although lipoxygenase is found in both animal and plant species, soybean lipoxygenase-1 (SLO) was used for catalyzing direct electrochemical oxidation of NEFA in conjunction with [Ru(bpy)3]2+. In this application, SLO breaks down the fatty acids found in metabolic lipids to produce fatty acid hydroperoxide. When used in conjunction with electrochemistry, NEFA becomes oxidized and detectable by the electrode. The biosensor’s other electrode, for detecting the ketone BHBA, uses another enzyme (HBDH) that is produced naturally by organisms under stress and that can be detected through electrochemical oxidation. The isolation that enabled BHBA to be detected uses the electrochemical oxidation of the coenzyme NAD+ to produce NADH. Because HBDH is dependent on the coenzyme, the electrode can readily identify the enzyme through covalent bonding at the molecular level. Determining the correct microvoltage supplied to the electrodes further enhanced the efficiency and reliability of the device. The result is a biosensor that can detect both NEFA and BHBA in less than a minute from a single drop of cow blood. Farmers and their cows will benefit Using our biosensor for on-farm testing for dairy cow diseases significantly reduces the stress on the animals, as it requires a only drop of blood (instead of a vial), and it provides rapid results. This ability to detect multiple disease biomarkers from a single drop of blood by untrained farmers is a unique advantage. In addition, the cost savings provided by early detection would be substantial for both small and large dairy herds. For large dairy operations, this technology can be combined with in-line robotic milking machines to monitor the herd collectively, avoiding the time-consuming method of testing each cow separately. Dairy cattle are an investment, and they must be kept healthy to maintain optimal production levels. Our new biosensor is the latest tool for dairy farmers to use in monitoring the health of their herds. This biosensor can be an important part of routine screening in dairy operations, and its ease of use and convenience will significantly enhance the management of dairy herd health. ASABE member Suresh Neethirajan, P.Eng., Program Leader (Biological and Biomedical Engineering), BioNano Laboratory, and Assistant Professor (Bioengineering), School of Engineering, University of Guelph, Ontario, Canada, firstname.lastname@example.org.
Published by ASABE. View All Articles.