Can I also use hay bales and not straw bales?

As per using hay…..strictly speaking one is not supposed to use hay ….because hay tends to biodegrade more easily. Generally hay is the more grassy part of the grain. Thus is not just silica and cellulose like straw but would contain more nutritious elements that will be more attractive to insects and fungal attack. Strictly speaking all the literature advises against using hay and recommends that one uses straw.