Jayme Sellen, spokeswoman for the Dairy Business Association, which represents Wisconsin dairy farmers, said the study just shows that all dairies produce safe milk and consumers shouldn't be concerned.
"The main point is that milk is extremely high quality regardless of the size" of the dairy farm, Sellen said. "And that's not surprising. We have some pretty high standards here in Wisconsin. We know our milk."
The study defined small dairies as those with 118 cows or fewer and large ones as having 119 to 713 cows. Extra-large farms with 714 or more cows require special permits in Wisconsin.
Overall, Wisconsin dairies tend to be smaller, with an average of 88 cows in 2007 compared to California's 824, according to the latest federal statistics.
Several Wisconsin farmers argued that keeping smaller herds gives them an intimate perspective that's hard for bigger farms to replicate.
Darin Von Ruden, a dairy farmer in Westby, Wis., said he knew the personalities of his 40 cows so well that if one acted the slightest bit unusual he could keep her milk out of the general collecting tank until he knew what was wrong.
"That might not happen at the bigger factory farms," the 43-year-old said.
It's not clear how much that kind of thing matters to consumers, who often judge milk on its taste and shelf life. And since pasteurization kills most bacteria, consumers might not care as much about the data Ingham analyzed.
"I don't care about all that. Milk is milk," said Cherie Kappus, 58, a secretary in a Milwaukee law firm. "I just check the (expiration) date. Otherwise, it's all the same."
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