That's very interesting!
I went to a talk the other day on nutrition and heard that crohns is more prevalent in areas where there is a high level of a certain bacteria, similar to T.B., in cows. So there is a theory (proposed by Prof Herman Taylor, St Thomas Hospital, London) that people who drink the milk from these cows have a higher incidence of crohns. Apparently crohns looks very much like TB in the bowel. It's also suggested that the cows that carry this bacteria are lacking in selenium, due to the decreasing levels of selenium in UK soil.
Anne