You are correct that  we should try and eliminate added iron in our horses diets whether they are IR and/or PPID or not, but since iron is in hays,pastures and feeds we use their analyses to balance the trace minerals (copper, zinc and manganese) to a tight ratio of Iron (4): Copper (1): Zinc (3): Manganese (3) as well as the major minerals to reflect the NRC requirements and recommended ratios based on ideal body weight, age and activity level of the horse for whom we are doing the diet.

Since TC 30 is a dense supplement feed the recommended feeding is 1 #  to 1.5#'s per day for a 1,000# horse.  The Iron is listed as 750 ppm, but that is a 340 mg of iron contribution to the diet per pound.  As you know the ODTBC have iron as well and the iron analysis for the one I found in the files lists the iron as 313 mg per pound.  The ODTBC is an excellent product and we would not eliminate it from our feed program based on the iron content alone because as you point out it is balanced. 

I think when our horses have a hoof soreness issue or something is just not right it is an excellent idea,  as Robyn has done,  to go through and evaluate our feed program, hoof trim, exercise and pursue a diagnosis to see what might be causing the problem.  If the 1# of TC 30 with an ESC (Sugar) of 8% and Starch of 1.8% is the possible cause then we can eliminate it and  source another carrier or supplement  product for our diet.  

Kathy Brinkerhoff

SE/WI  10/12