Dairy producers are doing something right. A recent study presented in September, 2011 at the 3rd International Symposium on Mastitis and Milk Quality, indicates that bulk tank somatic cell counts (BTSCC) have continued to decrease on U.S. dairy farms, which indicates an increase in milk quality. BTSCC refers to the number of white blood cells (primarily macrophages and leukocytes), secretory cells, and squamous cells per milliliter of raw milk and is used as a measure of milk quality and as indicators of overall udder health.
The study used data from four Federal Milk Marketing Orders (FMOs) which capture data from almost 50% of milk shipped in the U.S. BTSCC were evaluated at four levels: herds, shipments, orders, and milk. The milk-weighted geometric mean BTSCC was 295,000 cells/ml in 1997 and was 224,000 cells/ml in 2010, representing a 24% decrease.
Jason Lombard, DVM, MS, USDA-APHIS Veterinary Services, Fort Collins, Colo., says approximately 50% of shipments from each of the four FMOs averaged 200,000 to 399,000 cells/ml BTSCC, while less than 3% of all shipments in 2010 exceeded the current U.S. regulatory BTSCC limit of 750,000 cells/ml.
Automatic take-offs and parlor sanitation have also decreased SCC. Even summer variations, when higher temperatures and humidity increase stress on cows and provide conditions more favorable for bacterial growth, have also decreased over the years that were monitored, Lombard says.
Granted, this information is a bit biased, Lombard notes, because those federal milk marketing orders pay bonuses based on somatic cell counts, but three subsequent National Animal Health Monitoring System (NAHMS) studies have also indicated a decrease in BTSCC.
There seems to be a correlation to dairies that are more observant and those that have high milk quality, adds Angela Daniels, DVM, Circle H Headquarters, LLC, Dalhart, Texas. “The small things matter a lot. Farms that have good milk quality are good at mastitis recognition, maybe to a point where we are hypersensitive. They also have sound milking and treatment protocols in place and a good monitoring system that allows us to recognize when changes occur.”
Monitoring to find problems
There isn’t just one way to solve high SCC problems on the dairy. Daniels says it’s really important to know what the culprits are before trying to blindly solve the problem. “We advocate a monitoring program that includes regular bulk tank cultures, monitoring fresh cows for contagious mastitis and bacterial monitoring of mastitis cases,” Daniels says. “Additionally, having continuous access to the quality results from the milk processor are key to knowing what is going on.”
Daniels says with a monitoring program in place, there is an early alert system in place when something does change which allows you to know where to begin. “If you are working with a client who does not have this system in place, it is important to collect some diagnostics to know which direction to head.”
Changes in bedding, 1996 to 2007
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The ideal bedding for lactating cows is dry and clean, provides cushion and does not support bacterial growth. Of the bedding types listed in the table, only the use of straw and/or hay decreased from 1996 to 2007 on operations and for cows. The percentage of cows bedded on corn cobs and stalks decreased by about one-half from 1996 to 2007. The percentage of operations that used sand or mattresses increased, with mattresses showing the largest increase from 4.7% in 1996 to 23.7% in 2007. Composted manure use increased, as 9.0% of cows were bedded on composted manure in 1996 compared with 24.2% in 2007.
There are a lot of inputs that can impact SCC on the dairy, everything from bedding, cow health, environmental changes, milking equipment, sanitation and more, and it’s difficult to point to one area that makes the difference. “From my experience, it is dairy-specific and is generally multifactorial,” Daniels adds. She works individually with clients throughout the region to improve milk quality when opportunities arise
How clients have improved
Over the last five to 10 years there have been improvements in health, housing and technology that no doubt have benefitted SCCs on dairies. Daniels outlines how some specific activities have contributed to milk quality. “Clients realize the value of training programs,” she says. “In most cases our clients use full prep routines, we have better teat dips – particularly better winter/protectant dips, we are doing a better job washing towels and monitoring the cleanliness of the towels and the barn.”
As far as cow cleanliness and sanitation, Daniels says the industry agrees that sand is the best bedding material, but good advances have been made in using compost. “We also now have the tools to hygiene-score cows, there has been new technology introduced with pre-dipping and more attention to stall cleanliness.”
Daniels says the largest change she’s noticed is that we recognize the importance of tracking health data. “Laboratory results can now be automatically uploaded into the software systems, We have farms that have implemented on-farm culture that allows for making more targeted treatment decisions. We may be under-utilizing the value of DHIA testing which is a great tool to help monitor milk quality via SCC data on a monthly basis.”
Daniels believes that dairymen have always placed a high value on having high-quality milk. “Certainly the discussion of lowering the SCC limits brought the discussion of improving milk quality to the table,” she says. “The value of implementing many of these changes can certainly be realized by milk quality bonuses. The key for long term buy-in and success is to have cost-effective programs in place.”
NAHMS shows where we’ve improved
Jason Lombard, DVM, MS, USDA-VS, shares NAHMS data from the last three dairy studies, the latest which was Dairy 2007, and indicates the biggest areas of improvement which lead to lower BTSCC scores. A similar decrease in BTSCC has been observed over the course of the three NAHMS studies as was observed for the Federal Milk Marketing Orders. The majority of operations had an average BTSCC between 100,000 and 299,000 cells/ml during each of the three study years.
4 More operations are using automatic takeoffs in 2007 compared with 2002. Although there were no changes by herd size from 2002 to 2007 in the percentage of operations that used automatic takeoffs, the percentage of all operations increased from 36% in 2002 to 45.4% in 2007.
5 More operations (and more cows) are using (being milked in) parlors compared with 1996. The percentage of operations that used a parlor as a primary milking facility increased from 28.8% in 1996 to 39.5% in 2007, while the percentage of operations that used a tiestall or stanchion decreased from 69.5 to 60.3% during the same period. A larger shift was observed in the percentage of cows, as 54.9% of cows were milked in parlors in 1996 compared with 78.2% in 2007.
6 Although housing types don’t appear to have changed much as a percent of operations, a small increase in freestall operations and a decrease in tie stall stanchion operations could account for a large number of cows.
7 The percent of cows on sand bedding has doubled since 1996 – from 15.3% to 30.3%. The ideal bedding for lactating cows is dry and clean, provides cushion, and does not support bacterial growth. Of the bedding types listed in the table below, only the use of straw and/or hay decreased from 1996 to 2007, on operations and for cows. The percentage of cows bedded on corn cobs and stalks decreased by about one-half from 1996 to 2007. The percentage of operations that used sand or mattresses increased, with mattresses showing the largest increase from 4.7% in 1996 to 23.7% in 2007. Composted manure use increased, as 9% of cows were bedded on composted manure in 1996 compared with 24.2% in 2007.