Even more with blue grass, so much so that you just don't have to pet them entirely (-10 friendship maximum from not petting, and +16 from eating blue grass), though it's probably not too helpful for that purpose unless you're starting with meadowlands.
I wouldn't advise farming for them via monsters, however, as it's a really rare drop from already fairly rare special monsters. If you do find a nice monster floor and found one in a day though, you may consider experimenting with some fences as you can find the tile/s that they drop the autopetter on and can get like half a dozen in a day.