There are two and a half million cows in the Central Valley. Previous studies found each one generated about 13 pounds of gas annually that creates ozone smog.

Now, the San Joaquin Valley Air pollution Control Board says recent studies show cows create 20 pounds of gas each year.  Farmers aren't happy because the higher threshold would require many of them to spend additional money on pollution control measures. At a hearing in Fresno, farmers and dairy advocates said the new numbers are suspect.  J.P. Cativiela is with the pro-farm group Dairy Cares.

"More than three-quarters of the diary emission factor proposed by your district completely lacks scientific basis. Setting emission factors on information that is known to be flawed, helps no one."

The Control District says it stands by the numbers, but hasn't ruled out adjusting the emissions threshold. A final decision is expected by August first. If approved, agriculture officials say the new requirements would affect about a quarter of the region's 15-hundred dairies.