having had someone once tell me off for giving mine mown grass, I did explain that having a single cut action mower - farming term, basically it doesnt chop the grass into fine small sections, it cuts once like scissors do, they were fine for the small amount I had given them, but I know what I am doing so would never recommend mown grass.
I will explain how grass behaves after its cut, as soon as you cut into a blade of grass, it releases sugars at the site of the cut, this sugar is what causes the fermintation reaction to start and in effect pickle the grass. If you are making silage (pickled grass) you use a fine chopping mower to cut up the blades as much as possible and bruse the blades to get as much moisture and sugars out to make the silage the best quality (you want the moisture out to prevent it going mouldy, but not all the moisture). Over 3 days you agitate the piles of grass to bruse it further and release more of the sugars to pickle it.
Now Hay is also cut grass, but the difference is that it is cut using a single blade mower which cuts the grass at one point and leaves the blade of grass as long as possible. In this case you dont want the sugars to be released to start the pickling process, you want the moisture or water content to dry up as much as possible so the grass blades dry out completely and dont pickle. It is spread out during the day to dry in the sun, and piled up before nightfall to protect it as much from dew and moisture as possible before its spread out again, it takes 7 days to make hay.
Back to the scissors, they cut once, the grass is not pickled It is picked up (I have it all in my hand) right away so wont start to heat up either, and they can eat it perfectly well, I have been giving mine fresh grass from my lawn daily, just have to watch for slugs and snails
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