I don’t know what the hay grower’s situation is like on the Island; I’m sure there must be local hay production. In the Lower Mainland, there are a lot of options for what’s called “local hay,” meaning grass hay grown by smaller producers in the rainy zone of the Fraser Valley. Commercially grown timothy, orchard grass, or alfalfa comes from the dry zones in the BC Interior or Washington State. The commercially grown hays are often big three-string bales, 100-plus pounds. The “local hay” is usually two string bales, in the 50 lb range. The local hay is usually much less per pound than the commercial hay, especially if you buy direct from the farmer.
“Local hay” can be much higher in sugar, lower in minerals, and sometimes lower in protein than the commercial hay, because of the climate; the rain washes the minerals out of the soil (hence the low selenium content). You can however always get it tested, to see what it contains. Some of it is very good, some of it not so much.
As with the hay, the quality of pasture can vary a lot, depending on the soil, the water table, and the actual plants in your field. Some of our local wild grasses like Canary Reed Grass don’t have much nutrition; some of our fields get overrun with toxic plants like buttercups. Some fields have rich black silt from being in the river bottoms, while others are mostly sand/gravel glacial till. Some fields drain OK year round, others turn into ponds and can’t be used from November to April. And many people limit winter turnout to avoid destroying all the grass for the next year. I’m thinking about the Fraser Valley in all of this, but I imagine the same things would apply to Coombs, which is a similar climate.
The difference with Ontario would be that the fields will continue to look green all year around, but will pretty much stop growing over the winter. The grass will start up growing again in February or March, if there is no snow. If you have a large, well-drained pasture, and not a lot of horses, you can leave the horses out all winter without damage to the pasture. But if there are too many horses, or the ground is wet, you can make quite a mess of a pasture, so that it isn’t very productive the next year.
Anyhow, if hay is a big part of the diet, then you might also want to find out where the hay comes from, as the mineral profile might be different if you are feeding hay from the BC Interior.