Geoff,

Regarding: "Could it have been in response to pressure from some Tyson competitor with heavy political connections?"

With the growing trend AWAY from Growth Promoting Antibiotics (GPA), I would suspect that there is a LOT of pressure being brought about by the pharmaceutical manufacturers who have a lot at stake.

Schering-Plough, today announced the completion of their acquisition of Organon BioSciences, and the "Intervet" line of pharmaceuticals for animals, including Cobactan and Nuflor premix. The acquisition cost Scheiring-Plough 11 Billion Euro (cash). Schering-Plough says of the antibiotic premix, Nuflor, "Pigs receiving Nuflor Premix also grew twice as fast during the treatment and evaluation period, producing an average daily weight gain of 0.665 kg compared to 0.3353 kg in unmedicated controls." I doubt Schering-Plough has plans to curtail marketing of antibiotic premixes for animals any time soon. In fact, there might be strong motivation (11B Euros) to fight antibiotic bans at all levels.

If you read my post from September 11, 2007, entitled "Pharmaceutical Maker Rants against Call to Eliminate Subtherapeutic Antibiotics", you will get a taste of the public relations campaign being waged by Alpharma, another manufacturer of animal antibiotics. The pressure is clearly on the antibiotics manufacturers, and I suspect they will do whatever they can to reverse the international trend.

In another surprising move, the Pennsylvania Department of Agriculture recently banned the advertising of milk as dairy cows were not treated with artificial growth hormones. It seems the "organic" milk producers were getting more money for their milk by advertising it as "hormone and antibiotic free" and their competitors complaind, "it's not fair". So, in Pennsylvania, for the time being, producers are not allowed to advertise what their product does NOT contain. (Link to article.)

Tyson, as noted earlier this week, has expanded into Brazil, where there is currently less pressure on the use of antibiotics. Their acquisition of Pana Branca opens up the export market to China, just in time for the 2008 Olympics, and the anticipated US tourist boost to poultry meat sales.

I suspect we will see more maneuvers in the marketplace, as the pharmaceutical manufactures resist the trend (despite the risk to public health) and poultry producers plan for the future. Whatever the outcome, the poultry industry is looking at all of their options, and many of the major players are testing Agrastim as a replacement for subtherapeutic antibiotics.

-zties