There are many products out there. Not all are created with the health of your horse in mind. Simple is always better. In my practice I encourage your horse to be fed not supplemented. My standard recommendations are Co-op Caliber working horse ration. Aloe Vera juice and Flax oil. All other supplementation should be short term. 
I also recommend Equine Choice generation 2 pre probiotics. 
Equine Choice Generation 2 is available at Feed Store To Your Door. 

I have have also found the Rambo Ionic blankets to be very beneficial especially for those hormonal mares. Frontier Western Shop in Claresholm keeps them in stock and would be happy to help you out.  

I am am happy to book you an appointment to help find you the most efficient and cost effective natural program for your horse.