Hay is just meadow grass (and everything else that grows in it!) cut, dried and baled.
Readigrass, Graze On etc. are processed I believe - and are higher in protein (Friendly grass is 12%, the horse version is 15%) whereas something like timothy hay is about 7%. Not sure what 'normal' hay is though! So they can be fattening and also have higher calcium levels than hay (about the same % as pellets, so if you're feeding Readigrass AND pellets)...
This is what it says about Readigrass (which is 'pure' grass):
"The grass is dried quickly at high temperatures and immediately sealed in air tight water proof packaging, this technique allows the grass to maintain its high nutritional value, attractive natural green colour and the aroma of freshly mown grass, whilst also protecting the product from deterioration and contamination. Readigrass is available in convenient easy to handle 1kg. Readygrass has a higher nutritional value than hay, with a typical analysis as follows:
Protein 15% Oil 2.5% Calcium 0.8%, Fibre 20% Vitamin C 150mg/kg"
I experimented with feeding Readigrass instead of hay earlier this year after a few bad lots of hay and recurring cases of lice. They do enjoy it - but I found they missed the burrowing through the longer hay. Readigrass is ok as a food stuff but they so love it when I put fresh hay in for them to forage through, and it's just not the same.
There is also the question whether the shorter stalks of the Readigrass are as good as wearing down their teeth - I don't know the answer to that as I only tried it for a limited time. I'm back on hay now, but will supplement with readigrass in winter and also give it to poorly pigs to chomp on.
Sophie
x