Feeding cows to cows was how we got Mad Cow Disease.
Yes, it was specifically the nervous tissue causing that to happen, but perhaps we shouldn't be so blase about deliberately encouraging cannibalism
I'm kind of skeptical of the official cause. There was evidence that chemicals played a role, but the UK government wanted to shut down that speculation, so went with the 'it just happens' explanation. "The official panel found otherwise!" isn't a good model of how science is supposed to work. If it's literally
just animals eating other animals that's the cause of it spreading, and prions just fold themselves wrong
for no reason, then CJD should spontaneously occur in cows
all the time, e.g. there would have to be a first cow to start the chain, but we don't see cows spontaneously developing CJD at all, and other places have in fact fed animal waste to other animals, for sure, for a long time, yet nobody ever had this outbreak before.
The key alternate explanation is that excess manganese combined with copper deficiency causes copper to be substituted with manganese, and this leads to the problem.
https://www.ncbi.nlm.nih.gov/pubmed/25125459We have previously demonstrated in bovine brain homogenate that free radicals produce proteinase K-resistant prion after manganese is substituted for copper
This one is actually a good overview of the different theories:
https://www.copper.org/publications/newsletters/innovations/2001/12/mad-cow.htmlAnother position expressed in testimony before the BSE Inquiry and in the scientific and popular literature is that of a British organic farmer, Mark Purdey, who hypothesizes that:
A copper deficiency, with manganese replacement for copper in the prion protein, initially caused by the repeated application of extremely high doses of an organophosphate (OP) insecticide, phosmet, and the provision of a manganese-rich chicken manure-based feed supplement is the key to the origin of BSE in British cattle.
The subsequent feeding of MBM and offal from infected cattle containing OP derivatives and/or the manganese-modified prion protein caused its spread.
It is copper deficiency with manganese substitution that affects humans in the BSE variant, vCJD. Mr. Purdey believes that this is caused by low copper content and high manganese content in soil and consequently in food consumed by humans. Excess manganese entered the soil by the use of sewage sludge as a soil additive and of manganese-based pesticides.
So, this theory is that they were hitting the cows with high levels of insecticide phosmet to control a particular parasite (warble fly) which interfered with copper metabolism, and at the same time they started putting manganese-rich
chicken poop into their feed. This then caused manganese to substitute for copper in the prions and leads to the abberant folding and brain disease. Here's evidence that phosmet does just that to copper
http://enhs.umn.edu/current/5103_spring2003/prions/prionmetabolislm.html