First, purchase an Alberta Equestrian Federation membership. You can do this online by going to their website. Your membership will give you some automatic liability insurance as well as some discounts on other party insurance. You can also access important documents such as a livestock manifest for hauling as well as upcoming events, eqine activities, news and connections in the province.
For horse life and health insurance, I use Capris Insurance who I believe are based out of BC. Their service has been very good (although I have not had to make a claim). You my need an appraisal and a vet inspection prior tominsuring depending upon the value of your horse and the amount or type of insurance you purchase. They also offer additional insurance for tack, barns, etc. I chose not to opt for these extras as my home insurance gives me adequate coverage.
Trailers are usually covered by your vehicle insurance, however, call your insurance company to see if you will need to purchase additional insurance for a trailer. I also have additional property insurance that covers me for horse related liability on my property.