i too would try naturediet

I would also suggest soaking the beta and then using that to stuff the kong before freezing it.

You could try other things like mashed cooked carrots, minced cooked chicken, mashed banana (any could frozen or not)- try these things first though slowly before stuffing the kong.

If he is intolerant to wheat then beta surely isnt ideal? Its full of cereals and meat isnt even the top ingredient. If its suiting him then maybe he isnt wheat intolerent.

Arden Grange large breed (the equivelent of the beta) has chicken as the top ingredient and maize is the 3rd. Their sensetive food is free of all cereals, and has potato as the filler.

Burns (another one reccomended for sensetive tums). They do a chicken and brown rice - no maize.

hope it helps x