Question

I own an eight-year-old Percheron mare. She’s currently in midgestation, weighs about 1,800 lb (820 kg), and stands about 17 hands (172 cm). In addition to pasture, she receives 6-8 slices of hay a day (12-16 lb or 5-7 kg), 1 lb (0.45 kg) of a low-carb concentrate, ½ cup (4 ounces) soybean oil, some pasture, and a salt block. On this diet, she’s bright, in great weight, and healthy-looking. Problem: I have had issues with OCD in this mare’s foals. I am not sure if it is genetics, maternal nutrition during pregnancy, or nutrition of the foal during growth. Because of these problems, one of which just materialized in her yearling, I won’t breed her again, but I am considering using her eldest filly as a broodmare. Can you review this mare’s diet for me, please, so I can start somewhere?

Answer

As you alluded to in your question, osteochondritis dissecans (OCD) is considered a multifactorial syndrome, meaning more than a single factor can incite growth problems. In addition to genetics and nutrition, there may be an exercise or injury component. In certain instances, the cause can be pinpointed with confidence; other times, the trigger remains elusive.

First, in regard to your mare, consider these suggestions:

• The feed the mare is currently eating is recommended to be fed at 0.4-0.65 lb per 100 lb (0.2-0.3 kg per 45 kg) of body weight. By feeding at least 7 lb (3.2 kg) of this feed, you will be providing the vitamins and minerals she requires to complement the forage she consumes. Because you’re feeding much less than this—just 1 lb (0.45 kg)—she is not receiving those essential nutrients in sufficient quantities. The fact that she does not need the calories from feed indicates she’s eating plenty of forage. Therefore, the best way to add essential nutrients without adding excessive calories is through the use of a ration balancer pellet. Feeding recommendations vary among products, but about 2.5 lb (1.1 kg) of ration balancer will likely take care of her needs.
• Because this is the mare’s third foal, you probably know if she tends to lose weight as she advances through late pregnancy and lactation. If she can maintain her weight on forage and a balancer pellet through late pregnancy and lactation, this would remain an acceptable diet. If, on the contrary, she requires more energy during these times, you can always reintroduce a feed, choosing one appropriate for broodmares. Should this be the case, so long as she’s being fed the minimum recommended amount of feed, you can stop giving her the ration balancer.
• The soybean oil adds a bit of energy to the mare’s diet and enhances coat condition, and there’s no problem with keeping this in her diet. Allowing the mare free-choice access to salt, as you do, is recommended as well.

Second, I wanted to offer some recommendations for nutritional management of young horses to reduce incidence of OCD.

• Research has revealed that growth characterized by fits and starts might predispose a young horse to growth problems, including OCD. As such, the goal should be steady growth, and this involves close attention to the diet and regular monitoring of body condition.
• Choosing a feed properly formulated for young horses and then following the manufacturer’s feeding instructions is a sensible first step. Feed companies held in high repute often have a nutritionist on staff to formulate these feeds, ensuring they deliver the proper amino acids, vitamins, and minerals needed for growth without shortages or overages.
• Do not forget to give forage its due in the diet of a young horse. Lush pasture or high-quality hay may cause overfortification of certain nutrients, notably energy.
• If a young horse begins to gain weight on forage and the recommended amount of concentrate, a change in diet might be necessary, as excessive condition, and certainly obesity, in young horses can instigate growth issues. In these instances, a balancer pellet is useful, as it provides all of the protein, vitamins, and minerals needed for growth without excessive energy.