I'd like to know who funded the study before I proclaimed that multitudes of cattle cause no harm to the environment. Either way, just on stench and flies alone I'd like to see dairies out of the San Joaquin Valley. I live downwind of one, and it's awful. I don't use milk or milk by-products. They aren't necessary for good health and in fact contribute to the poor health of many Americans. Drinking the milk of animals is obsolete and disgusting.

Thanks for responding. You raise good points. I don't think scientists are proclaiming multitudes of cattle cause no harm. The study just identifies the feed as the major source of the ROGs, and that means the manure is not the major source of that pollutant. There are separate and ongoing arguments over the smell and regulation of chemicals such as ammonia.

The funding for the study came from the U.S. Department of Agriculture.

I'm not sure that this study provides any support to the claim that cars create more reactive gases than cows. Just because the majority of the pollution comes from silage doesn't automatically mean that cows aren't contributing more than cars. Were there any direct comparisons between cows and cars? If not, then your original statement from 5 years ago might not be wrong at all. The only new information is that the cows don't contribute as much as their feed.

The comparison between cars and feed is in the Results and Discussion section of the study on the Environmental Science & Technology site. Those are the two numbers I cited. The study can be reached through the second link above.

The belches and farts of the cows still produce a lot of ozone forming gases. This is due to eating the silage that plays havoc on their digestive systems. Put cows back on a nearly 100% grass diet and pollution from cows and their feed becomes a non-issue. It would also raise the quality of the milk (less puss and more protein). The federal subsidy system that rewards maximum milk production over quality is partly to blame for these problems. No meaningful regulation of pollution from factory dairies is the other part of the problem.

Thanks for your reply. I definitely appreciate your reporting on this issue. It's so important.

I see the comparison between cars and feed, but your original assertion 5 years ago was that *the cows* produced more reactive gases than cars, and that was what readers took issue with.

I wanted to point out that the comparison between cars and feed doesn't lay to rest the possibility that the cows themselves are still producing more than cars. It just means that all of the reactive gases from dairy aren't coming from the cows themselves. How much do the cows themselves contribute, and how does that compare to cars? Perhaps we're still awaiting the data (it certainly seems painstaking to collect).

I'm certainly not defending automobile transportation here. All the waste of one-car-one-driver is also something we need to address.

The question about the funding is a good one. The Dept of Ag is definitely in the corner of dairy producers and there's a lot of heavy lobbying. It's always good to be skeptical.

Thank you again for your continued reporting on this issue.