South Dakota Cooperative Extension Dairy Specialist Alvaro Garcia said that even when feeding calves, some dairies process the milk they use to avoid the possible spread of a wide range of pathogens.
"A 2007 report by the National Animal Health Monitoring Surveillance System found half of the dairies that fed waste milk to calves pasteurized it in an effort to reduce the risk of infecting calves with pathogens," said Garcia. "A recent trial conducted in 2004 evaluated the effectiveness of on-farm pasteurization to destroy mycobacterium, salmonella, and mycoplasma in raw milk."
Garcia said the study found that pasteurization resulted in colostrum and milk with no viable pathogens detected, suggesting this method is effective to generate a safer product to feed nursing calves. "These same pathogens are also frequently responsible for bacterial food-borne illnesses in humans," Garcia said. "In addition, Campylobacter is another pathogen that is increasingly connected to food-borne illnesses."
According to the Center for Disease Control, Campylobacter infection is currently the leading cause of bacterial gastroenteritis in the U.S. "Between 1973 and 1992, there were 80 outbreaks of Campylobacter , and 38 percent of those were traced to raw milk consumption," said Garcia. "A potential result of this infection is Guillain-Barré Syndrome that results in acute paralysis of nerves and muscles"
Garcia said that Guillain-Barré Syndrome affects approximately 1-2 people out of every 100,000. So far this year, Campylobacter has already been responsible for 64 cases in South Dakota, a 36 percent increase over a five-year median of 47 cases. Health officials report a higher likelihood of the problem between May and September.
"Campylobacter is commonly found in the intestine of animals, so the usual common route of transmission is fecal contamination of water or food, particularly raw meat, poultry, or milk," Garcia said. "In the 2007 NAHMS profile on dairies, looking at a total of 1,885 healthy dairy cows, 33.7 percent of those cows tested positive for Campylobacter."
Garcia added that dairy cow management and milk harvesting practices have greatly improved over the years. "Milk is safe, provided it is handled properly once it leaves the farm," said Garcia. "But dairy farms are far from 'sterile' as bacteria are present in the cows and the environment, and in spite of best management practices, there's always the chance that pathogenic organisms can find their way to the milk tank."
Garcia said milk and dairy products must receive proper processing to minimize the possibility of human health risks.