About six months ago, our family purchased an 11-year-old Quarter Horse mare (14.2 hands or 147 cm; 950-1,000 or 430-450 kg) to be shown as a cowhorse. She was in moderate body condition, a score of 5, when we bought her, but she had poor muscle tone. She has bulked up to a body condition score (BCS) of 7+, and she has improved muscle tone. She’s ridden three or four times a week. She is fed a quality alfalfa/grass mix hay, 0.5 lb (0.23 kg) of a four-in-one supplement, 0.5 (0.23 kg) of a sweet feed, 1 oz of biotin with added vitamin C, and one-third cup (80 ml) of soybean oil per day. Here’s the rub: she is easily spooked, whether in the arena, on the trail, or just tied. Her sire is the same way, as well as several of his offspring, so I guess you could say she comes by it honestly. We give her an injectable joint product monthly. How could I adjust her feed to help calm her yet still meet her nutritional needs as I work to get her ready for the show season?
Your mare has been able to gain weight and muscle tone under your care and with her current diet, and that is a compliment to you. A BCS of 7+ is creeping into the fleshy to fat range, and this might prove to be a little heavy for her, especially since she has problems with arthritis. Show horses tend to be kept slightly heavier than moderate body condition, which would be considered a 5, but her excessive weight and her spookiness might be related.
Feeding in excess of calorie needs, as evidenced by her weight gain, can be one explanation for increased reactivity and spookiness, especially if a horse is stalled for the majority of the day with limited turnout.
To reduce her weight slightly to achieve a BCS of 5 or 6 and to moderate her spookiness, I would consider feeding her a hay composed completely of grass. Alfalfa typically provides more calories than grass hay, so her current forage might be adding excessive energy to her diet. From your query, I’m unsure of how much hay she is fed, but for a mare her size, she should be allotted 12-20 lb (5.5-9.1 kg) each day. If she cleans this up quickly and is left with nothing to eat for several hours at a time, feed the hay in one of the many "slow-feed" haynets available. These haynets have proven effective in slowing forage consumption, which stretches the amount of time it takes for horses to eat hay and keeps the gastrointestinal tract moving for longer periods of time.
I assume you are feeding the sweet feed (0.5 lb or 0.23 kg) as a carrier for her supplements, as it is being provided way below the manufacturer’s feeding guidelines to provide complete nutrition. The supplement appears to be a four-in-one product designed for vitamin and mineral, hoof, joint, and hindgut supplementation. The nutrient specification does indicate that it fulfills vitamin and mineral requirements; however, it does contain more copper than typical equine products, especially when compared with zinc. Generally a copper-to-zinc ratio of 1:3-4 is recommended for horses.
Because it sounds like your mare is an easy keeper, I would recommend providing a ration balancer fed at 1-2 lb (0.45-0.9 kg) per day to provide complete and balanced nutrition. Alternatively, if you prefer to offer a sweet feed for mixing supplements, then Micro-Max is an excellent source of concentrated vitamins and minerals to top-off nutrient fortification. (In Australia, look for Gold Pellet.)
The soybean oil (1/3 cup or 80 ml) is not adding a large number of calories. If your mare maintains her condition on a predominately hay-only diet, then these are unnecessary calories, and is probably being fed to promote coat condition, as biotin does. You could discontinue use of the soybean oil.
The supplement information you provided reveals some overlap. Feeding the four-way supplement, biotin, and biotin-C products is edging close to oversupplementation of certain nutrients, including biotin, which is only effective up to a certain amount each day (20 mg). There is anecdotal evidence that thiamine (vitamin B1) can have a calming effect in anxious horses, and some horses respond positively to supplementation of thiamine and magnesium, commonly included together in commercial calming products.
In sum, to simplify this mare's diet and perhaps take the edge off of her reactivity, I suggest (a) switching her to an all-grass forage fed at 1.5-2% of her body weight, (2) discontinue the use of the soybean oil; (3) provide a balanced diet either by offering an appropriate ration balancer (1-2 lb or 0.45-0.9 kg per day) or vitamin and mineral supplement; (4) continue feeding one of the biotin supplements so that she receives 20 mg of biotin per day; and (5) if you believe she would benefit from further joint support, in addition to the injectable, I would suggest Synovate HA and KER-Flex. (Australian horse owners should look for Glucos-A-Flex.)
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