I don't know much about gluten, but there is sulpher in it and you
should feed a different kind of mineral because of that.
Good luck with him, I hope he gets better.
Be very interesting to find out what's going on with him.
I did find this from the OSU Extension website:
The concentration of crude protein is about as twice as high in corn gluten feed as it is in corn grain. The amino acid content of corn gluten feed is about two times higher than in corn, but relative concentrations of the amino acid are similar. Like corn, the quality of the protein (for example: low lysine) is poor. Corn gluten feed is low in calcium but has significant amounts of phosphorus. The calcium to phosphorus ratio is about 1:10. The desired ratio of feeding cattle is a minimum of 1.5-2 to 1 calcium to phosphorus. Therefore, corn gluten feed fed at high levels without calcium supplementation could result in urinary calculi problems. You will have to feed calcium levels above NRC minimum requirements if more than 1/3 of the diets is corn gluten feed. Trace mineral and vitamin levels can vary greatly from batch to batch.
http://beef.osu.edu/library/gluten.html
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So if your mineral is high in Phos, they probably aren't eating enough to
get their trace minerals (mag being a trace mineral) and you could
be looking at a winter tetnany type of thing. We had this happen to
a cow herd that was being fed straight wheat hay. They had some cows
go down because of winter tetnany. The wheat hay contains a lot of
phos and they weren't eating enough mineral to get their trace minerals
(phos being a limiter).
We had them go to a lower phos mineral which they ate. It balanced
their system and the cows quit going down.
We have a mineral with no phos (0%) that is recommended for cattle
being fed corn gluten.
Hope this helps!