Wisconsin BST Use Doubles in Four Years

December 29, 1999

A University of Wisconsin study shows the use of recombinant bovine somatotropin (BST) in the state more than doubled between 1995 and 1999. About 15% of Wisconsin dairy cows now are treated with BST and about 15% of farms have adopted the technology.

Farms with larger herds have been more likely to use BST than smaller farms, the study shows. More than 70% of the herds with more than 200 cows now use BST. Larger farms have been consistently more likely to adopt the technology since it was introduced in 1994, says Marcy Ostrom, outreach specialist at the university's program on agricultural technology studies.

On farms with fewer than 50 cows (which still make up more than 40% of Wisconsin dairy farms) only 4% of the operators use BST. About 10% of farms with 50-99 cows used BST in 1995; that reached 16% in 1999. Ostrom says BST use on farms with 100-199 cows increased from 21% to 31%.

In 1997, farmers who used BST reported using it on 48% of their cows. Combining the larger average herd size of adopters with the 48% use rate indicates that about 15% of cows in Wisconsin now are being treated with BST, says Ostrom. Assuming a 10% increase in milk supply from BST use, the hormone may be accounting for less than a 2% general increase in Wisconsin milk supplies.