I look for oils that are higher in omega 3.....flax and canola are good sources and fish is best. Most horses get plenty of omega 6 in their feed and benefit from the added omega 3. Omega 3 has anti-inflammatory properties at the proper ratio to omega 6, while on the flip side omega 6 can cause inflammation if you get beyond the 10:1 ratio (omega 6 : omega 3).
Thus far no studies have shown that you can give too much omega 3.
My guys are on either dac Oil or dac bloom year round. dac Oil Fatty Acid Supplement 7.5 lb - Omega Horse Solutions dac Bloom Weight Gain, Muscle Tone, and Growth