In answer to your question about molasses being bad for endurance horses. There has been no scientific research that I know of done on feeding molasses to endurance horses. There are certain well known individuals that, when up on their soap boxes, can be really hard on molasses, but their concerns are mostly unfounded in research. If molasses were bad for the endurance horse then how could the World Champion who has been on the same sweet feed for several years (7% molasses) being doing so well? There are many endurance horses here on the east coast which are fed sweet feeds without any detriment to their performance.
In knowing the physiology of digestion of carbohydrates and nature of molasses I have a hard time believing that the small amounts to the feed (5-12% for sweet feeds and 2-4% for pelleted feeds) could make that much difference in the performance of the horse. Pound for pound, molasses has fewer calories than corn, less protein than oats, and twice as much fiber as corn. Total digestible nutrients (TDN) for molasses is only 54%, while corn is 80% and oats are 65%. I can understand how molasses can get a bad rep because it is sweet tasting and it is very palatable to horses. One might think that the horse is getting a dose of pure sugar, but as stated previously, that is not so. Molasses is what is left after most of the sugar has been extracted.
We at Kentucky Equine Research have studied the effects of different feeds and feeding times on blood glucose and insulin. Feeding of grain (the same scenario goes for molassed or unmolassed feeds) causes a surge in blood glucose. When blood glucose goes up then insulin is released to promote the storage of the glucose for later use. As the blood glucose level drops, so does insulin. The more grain fed, the higher the glucose and insulin peaks. There is some evidence that these rises and falls of insulin and glucose can have effects on the brain, causing the horse to have greater mood swings. These changes in glucose and insulin are not nearly as dramatic when the horse is fed hay. This may explain some of the difference in personality when a horse is put on a high grain diet. The amount of molasses in the feed does not appear to influence the height of the peaks for glucose or insulin. Horses fed pelleted feed, which has much lower levels of molasses, exhibit just as much "grain mania" (irritable, excitable, impatient, crazed, etc.) as when fed sweet feed.
I cannot help but wonder if some of the fear of feeding molasses to endurance horses has to do with the misconception that feeding molasses is like giving a candy bar and reinforcing the overwillingness of an incredibly fit horse to go. Actually, what may be thought of as an effect of molasses may simply be an effect of grain feeding (sugar and starch). If you have heard other theories as to why molasses might be bad for an endurance horse, I would be interested in hearing them.
Kathleen Crandell, PhD, email@example.com
Kentucky Equine Research