The answer seems to be whatever is reported by the largest number of media outlets, mainstream and alternative. I'm just wondering aloud about my personal misgivings. (For those who insist on facts and figures only, you can stop right here, and have a nice weekend.)
The official story of radioactive rice hay is as follows:
The rice farmers left the rice hay in the fields after the harvest last fall, because the weather was supposedly not good. Too much rain, not enough time for the hay to dry.
When Fukushima I Nuclear Power Plant reactor buildings blew up, the rice hay was sitting on the ground. Then the rain and snow fell on the hay, contaminating it with radioactive materials.
The rice farmers collected the hay and sold/gave it to cattle farmers, who then fed the rice hay to their cows to improve the texture of the meat before the cows are sold to the market.
The cows were later found with radioactive cesium, and it was determined that it was from the contaminated rice hay that they ate.
Here are my problems:
If the rice hay had been sitting on the ground since August/September last year and it rained and snowed, wouldn't the rice hay pretty much rot by March this year?
The radioactive rice hay, particularly that from Miyagi Prefecture, has been shipped all over Japan. Why? Because, apparently, the rice hay from Miyagi (and Iwate) is considered high quality because the rice there is considered premium. Cattle farmers outside Miyagi purchase the Miyagi rice hay to feed their premium cows. This cattle farm in Yamagata proudly says their premium cows are fed with only quality rice hay from Miyagi and Yamagata.
Would the cattle farmers all over Japan buy the rice hay that was sitting on the ground for more than 6 months in rain and snow?
Another problem I have is that these cows start to be fed with rice hay one year before they are sold to the market. The cows that were found with radioactive cesium in July were sold and processed into meat between April and July. So they must have been eating rice hay since March - July of last year, and ate the radioactive rice hay for less than 3 months at most. Many cows were sold and processed in April, so they ate the radioactive rice hay for less than a month.
It turns out that Miyagi Prefecture is the number one producer of rice hay for cattle feed in Tohoku. Even if the rice hay producers do not roll the hay until it's ready to be shipped, I would think they keep it indoors at all times.
The government says it's the rice hay that contaminated the cows, the media outlets say so too. Producers, wholesalers and retailers of domestic beef all say so.
The cows got contaminated, and the rice hay got contaminated. But they may be the two separate events, and may not have happened the way people say it happened. Just my non-expert musings.