by Tamara Scully
The somatic cell count (SCC) of milk increases if there is mammary gland inflammation in the cow. SCC is a “good marker of mastitis,” Susan Schexnayder, University of Tennessee, said in a recent DaireXNet presentation, “New Insight Into the People Side of Milk Quality.” “Mastitis is directly related to the quality of milk…and it decreases milk quality and yield.”
Schexnayder conducted research in the Southeastern region of the United States, which has the highest SCC numbers of any region. States in the southern region range from 18 to 46 percent of their milk testing above a 400,000 SCC threshold.
The 400,000 SCC threshold is the cut-off for acceptable milk quality in Europe, and is also the threshold where “many cooperatives and processors set their milk quality initiatives,” Schexnayder said. “The Southeast has not kept pace with the rest of the U.S. in producing milk with a low SCC.”
Attitudes and mastitis
In an attempt to understand this discrepancy, Schexnayder focused on behavioral and operational factors which might explain why individual dairies themselves tend to be very consistent with their SCC levels from year-to-year, but that neighboring farms with apparent similarities were often at the low and the high end of the bulk tank SCC spectrum.
It is known that herd management and hygiene practices impact mastitis incidents, and that implementing measures which improve overall cow comfort and cleanliness will result in lower bulk tank SCC. Neighboring farms are presumed to have the same access to resources which could help farmers reduce the causes of mastitis and lower SCC counts.
But often, neighboring dairies demonstrated “very divergent milk qualities,” Schexnayder said, indicating that “what we know doesn’t always match what we do,” potentially resulting in the wide range of bulk tank SCC levels seen in the Southeast.
With milk cooperatives rewarding lower SCC via milk quality premiums, why aren’t some producers with SCC levels over the threshold taking steps to lower their counts? What else factors into decisions which impact bulk tank SCC?
Through small-group discussions, facilitated via a fixed format, as well as a survey of over 600 dairy farmers in the Southeast region, spread across six states, Schexnayder focused on farmer or manager behaviors, as well as on dairy operational structure, to find if these people factors might influence SCC discrepancies. Farms in the study had SCC levels from 130,000 to 700,000 SCC, based on farmer self-reporting.
“We’re focused here on the characteristics of the operations and their decision makers that underlie the adoption of these herd management practices,” Schexnayder said. The researchers were able to identify “a set of factors…that actually explain about 65 percent of the variance, from farm to farm, of bulk tank SCC.”
One primary factor found to account for the large variability in SCC between dairies was the level of SCC tolerated before action would be taken. On farms where the operator felt action was needed below 300,000 SCC, the SCC levels remained well below the acceptable 400,000 threshold.
However, if farmers indicated that action was not needed until bulk tank SCC rose above 300,000, they had difficulty lowering their counts. Milk cooperative incentive structures did influence farmer behaviors, as did the perceived costs of taking measures to decrease SCC, leading many farmers to postpone taking action, or to accept a higher SCC level as acceptable for their operation.
“The decision makers are often looking at a ‘sweet spot’ where they can maximize their profits,” Schexnayder said.
“Early interveners actually see results.”
Farm structure and operation characteristics
Sole proprietor dairy farms had SCC levels lower than other business types, with a decrease of about 13,000 SCC associated with sole proprietorship. On farms where the owner or manager was sometimes in the parlor, SCC levels decreased by 14,000.
For operations which also included enterprises not related to dairying, the SCC count was found to increase by 11,000 over farms where the entire operation was dairy-related.
On dairy farms where the owner also worked off-farm, there was no increase in SCC levels seen.
“This research does not suggest that off-farm income correlates to increased SCC,” Schexnayder emphasized.
Farms with non-native English speaking workers, where the owner was a native speaker of the English language, had lower SCC levels than farms where employees and owners both were native English speakers. Having English-speaking employees increased the bulk tank SCC by 13,000.
“When the owner and the manager are speaking the same language…the bulk tank SCC tends to be higher than the average bulk tank SCC. What we don’t know at this point is whether there are different training programs in place, or other factors associated with language, that have to do with this finding,” she said, indicating that perhaps some cultural factor might account for the lower SCC on farms with Spanish-speaking employees.
The study did determine that three factors — having a mastitis training program in place on the farm, delegating mastitis treatment to the employee, or evaluating employees on bulk tank SCC practices — were not handled differently on farms with Spanish-speaking employees than on those with native English speakers.
Operations planning on remaining in business five years out had lower bulk tank SCC than farms that planned to stop milking. Those who planned to leave the industry prior to five years time demonstrated a SCC increase of 13,000 over those planning to dairy long-term.
Those farms planning on staying in business also produced six pounds more of milk per cow, per day, than those leaving. Those not continuing had smaller herd sizes compared to those planning to continue milking. On farms with a short-term exit plan, a higher SCC was tolerated, with these farmers indicating that 400,000 SCC was the point at which they’d take action.
Schexnayder’s research also sought to shed light on why the Southeast consistently has higher bulk tank SCCs than any other region in the nation. Virginia and North Carolina had the lowest SCC counts of the states in the study. While this may have been related to being at a more northern latitude and presumably having less heat stress, which can increase herd SCC, Kentucky, located at a similar northern latitude, did not show the decrease in SCC over more southernly locations.
Farmers who reported receiving most of their mastitis information from veterinarians showed a 26,000 reduction in SCC over those who did not utilize veterinarians as a primary source of information. Those who used Cooperative Extension showed a net SCC decrease of 9,000 over those who did not seek out guidance from this source.
Farmers who felt empowered to take action and knew what to do to decrease mastitis levels demonstrated lower bulk tank SCC than those who either felt mastitis control would be too expensive, or too difficult, to manage. Education to focus on the affordability and implementation of mastitis management may help to reduce bulk tank SCC.
“Your attitudes about your ability to control it (mastitis) actually make a difference,” Schexnayder said.