need advice

i have a few problems with my buns
they seem to only use litter tray when lined with straw
trouble is the straw is thick and long strands and they just eat it!!
which ultimately means they are not eating their hay!!
dont know what to do for the best-they have already ruined my carpet with wee stains before we tried the straw-if only they werent eating it!!! grrrrrrrr

Give them straw in the litter tray, and hay in a hay rack above the litter tray?

It doesnt matter if they eat the straw, it just has no nutritional value.

From their favorite spot, put a vinyl at the bottom. Then put 2 towels soaked w/ their urine. Just change the towel often as they pee on the towel from now on.