Increasing milk production and buyers’ inability to continue to move excess milk out of state is expected to reduce Idaho’s dairy herd by 10,000 cows in the next few months.he cause is an increase in milk supply and the inability of buyers to continue to move any oversupply to surrounding states because of high costs. Buyers have done that in the past to balance markets during the peak production period of spring through fall, he said.The bottom line is that even without a significant increase in cow numbers, dairymen’s efficiency in turning feed to milk continues to increase milk production per cow. Idaho is now at a point where increasing milk supply is forcing dairy farmers to sell off cows, he said.