The average herd size for dairy farms in the United States keeps growing while the number of farms continues to decline. This trend is unlikely to change. Take a look at the Upper Midwest. From 2000 to 2012, the percent of state milk production coming from farms with more than 500 head grew nearly threefold. According to USDA data, the percentage of milk produced by farms with more than 500 cows in Iowa grew from 5.0 percent to 44.1 percent; in Minnesota, from 8.5 to 32.6 percent; in South Dakota, from 26.0 to 75.2 percent; and in Wisconsin, from 9.0 to 38.1 percent.
Larger operations, those with more than 2,500 cows, accounted for only 0.2 percent of operations in the four-state region but produced more than 11 percent of the total milk.
Some people worry that cows living on large dairies are more at risk for disease and poor welfare compared to cows on smaller farms. To address this concern, University of Minnesota's Marcia Endres and her graduate student Tyler Evink conducted a cross-sectional study of 15 dairies with more than 2,500 cows in the Upper Midwest. These farms represented 33 percent of operations of this size in Iowa, Minnesota, South Dakota and Wisconsin.
The average herd size was 4,972 cows, ranging from 2,606 to 13,266 cows. Average daily milk production per cow was 70.3 pounds, with 3.85 percent fat and 3.15 percent protein. Bulk tank somatic cell count averaged 190,000, and average 21-day pregnancy rate was 21.7 percent.
Eight of the farms housed cows in mechanically ventilated (either cross-ventilated or tunnel-ventilated) barns, while the other seven used naturally ventilated freestall barns. Seven farms used deep-bedded sand, seven used deep-bedded recycled manure solids, and one used 2 to 3 inches of recycled manure solids on top of mattresses.
Some indicators the researchers focused on to evaluate animal welfare were lameness, hock lesions and hygiene. They found a low prevalence of lameness, 16.7 percent overall, and only 5.1 percent severe, which is low compared to farms in previous studies. Dairies with a trimmer on-site had lower lameness prevalence than those that hired an outside trimmer. With a trimmer available at all times, lameness cases were likely addressed sooner, resulting in a lower lameness rate.
On these 15 farms, hock lesion prevalence was 22.8 percent and severe hock lesion prevalence was just 2.3 percent, which is below farm averages found in other studies. Hygiene score averaged 2.5, which is also good compared to previous research.
Based on these indicators, the researchers concluded that welfare is not compromised on large dairy operations in the Upper Midwest, which is really great news for our ever-changing dairy industry.
The author is an associate editor and covers animal health, dairy housing and equipment, and nutrient management. She grew up on a dairy farm near Plymouth, Wis., and previously served as a University of Wisconsin agricultural extension agent. She received a master's degree from North Carolina State University and a bachelor's from University of Wisconsin-Madison.
