By Andrea Tholen, Amber Yutzy, and Greg Strait, Penn State
On-farm milk culture is a tool that can help you reduce the amount of antibiotics being used, decrease costs associated with clinical mastitis, and increase milk quality and profitability.
Have you ever treated a case of clinical mastitis but weren’t sure what type of bacteria was in the quarter? Have you asked yourself, "Was that treatment I just infused really effective at treating clinical mastitis?" What if the cow’s immune system had already cleared the infection? On-farm culture is a tool that is gaining more appreciation across Pennsylvania and can help answer questions like these.
Mastitis is defined as an inflammation of the mammary gland and is prevalent in dairy herds around the world. Mastitis can be caused by a wide range of bacterial pathogens or from a physical injury to the mammary gland and/or teat end. Clinical mastitis is one of the most costly diseases affecting the dairy industry, with recent estimates suggesting each case is associated with a $231 to $289 loss (Hogeveen et al., 2010). Producers suffer economic loss through reduced production, discarded milk, veterinary services, culling cows, and treatment use. Mastitis is associated with the most frequent antibiotic use in dairy cows (Mitchell et al., 1998). One study found that milk discarded due to antibiotic treatment could exceed $100 per cow per year (Bartlett et al., 1991). Antibiotics are frequently used to treat clinical mastitis; however, oftentimes antibiotics are either ineffective or not needed to treat the disease. Producers that use unnecessary antibiotics lose profit due to discarded milk and can contribute to antibiotic resistance. Results in one study found 10 to 40% of cultures from clinical mastitis showed no growth following culturing (Roberson, 2003). Cultures that show no bacterial growth will typically require no treatment.
Identifying the species of bacteria that are responsible for causing a mastitis infection can be beneficial in determining treatment options and reducing unnecessary antibiotic use. Traditionally, producers will send milk samples to local laboratories for culture results. One downfall of laboratory testing is the time lag from milk submission until results are in producers’ hands, which can take several days. If a producer wants to treat based on the results of a culture they will have to wait several days. This time lag associated with laboratory results contributes to producers making uneducated treatment decisions. Adoption of an on-farm culture program could help producers make proactive treatment decisions and make them in a timely manner. Additionally, submitting a sample for bacteriological culture can be costly for a producer as they are charged a submission fee and shipping costs. On-farm culture will not only save the costs of discarded milk and treatments, but will also eliminate submission and shipping fees.
A study recently published in the Journal of Dairy Science examined the effects on-farm culture programs had on antibiotic use, milk withholding time, and short-term clinical and bacteriological outcomes. This study found through the use of on-farm culture, antibiotic use was reduced by half, milk withholding time decreased by 1 day, and no significant differences were found between days to clinical cure for treating cows immediately or waiting one day for culture results (Lago et al., 2011). While this study did not report antibiotic costs, cutting antibiotic use in half would suggest a decrease in treatment costs.
Penn State Extension dairy herd health educators Andrea Tholen, Amber Yutzy, and Greg Strait recently received a grant through Northeast SARE titled, "The adoption of an on-farm culture program by small and medium sized dairies in Pennsylvania to make proactive decisions regarding treatment." The grant covers the cost to setup 8 different herds across the state with an on-farm culture system. Farms will culture all cases of clinical mastitis and treat cows based on the on-farm culture results. Field days will be held at 4 of the 8 participating farms in early November. Dairy industry personnel and producers are encouraged to attend to learn more about on-farm culture and benefits the culture system is having on participating farms. The objectives of the grant are to reduce the amount of antibiotics being used, decrease the costs associated with clinical mastitis, and increase milk quality and profitability across the state.
So how do I get started with an on-farm culture program?
Penn State has created a quad plate culturing system for dairy producers. Each quadrant of the plate has the ability to selectively grow different species of bacteria. Quadrant I, MacConkey’s Agar (MAC), detects Gram-negative bacteria such as coliforms and non-coliforms. Quadrant II is Edwards Modified Agar (EMCO) and detects Streptococci bacteria. Quadrant III is Baird Parker Agar (BPA), which detects Staphylococci bacteria. Finally, quadrant IV is Blood Agar (BA) capable of growing most types of bacteria and is used to confirm results of other quadrants.
In order for a producer to get started culturing they will need the following supplies: sterile test tubes to collect aseptic milk samples($0.20), sterile swabs to plate milk onto agar plates ($0.10), agar plates to grow bacteria ($2.00 to $2.50), and an incubator that remains at a constant temperature to grow bacteria ($50 to $500). Once a clinical milk sample is aseptically collected, it should be plated onto a quad plate. Plates should be incubated for 24 hours and then observed for bacterial growth. Penn State has also created a free user guide which can help producers identify bacterial growth on their plates. Farm personnel handling on-farm culture responsibilities should consult with their herd veterinarian in order to make appropriate treatment decisions for their herd based on culture results.
The Penn State Extension Dairy Team offers 1-day culture workshops that teach producers how to take an aseptic sample, how to properly set up milk culture plates, how to read plates, and how to write a treatment standard operating procedure. To learn more about on-farm culture or to inquire about an upcoming on-farm culture workshop contact Andrea Tholen - Mercer (724-662-3141), Amber Yutzy - Huntingdon (814-643-1660), or Greg Strait - Fulton (717-485-4111).
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