I found this amazing website last year. The information is so helpful even if it is 'American' I have printed it and kept it in my paddock management folder.
http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex8017 It will be extremely useful I guess especially if you live in alberta. I don't even know where that is. The only thing I will say about the stages of grass growth is that some of my grasses are much shorter so page 10 has to be modified for me. 3 inches is the max height of my pony grasses! It still gives me the basic concept of grazing the elongation phase and trying not to stress the grass. Sue Coombes