I have a 21-year-old Thoroughbred mare that came to me five years ago badly starved, and she has had the hardest time putting on weight. I have tried so many different things! Her health is good, she is dewormed regularly, and her teeth are taken care of. I have her on senior feed, alfalfa (lucerne) cubes, beet pulp mixed with corn oil, and recently started rice bran and three flakes of hay in the morning and night. She will gain a little bit of weight then stop, and maybe gain a bit more a month later. Is there anything else I can do to put more weight on?
You’ve been able to alleviate health and dentition as concerns (vaccinated, dewormed, and received regular visits from the dentist), so we’ll focus on her age and diet.
As horses age, their ability to extract nutrients from their diet declines. Likewise, the amount of digestible energy (DE) needed for weight gain increases as horses age. Currently, you are feeding the feedstuffs that we would normally recommend for putting weight on an aged horse: a senior feed, alfalfa cubes, beet pulp, corn oil, rice bran, and hay. The problem you may be experiencing may be in the amounts you are feeding.
At this age and with this horse’s history, you cannot depend on hay alone to put a lot of weight on a horse as it is an essential component of any diet and key to maintaining a healthy hindgut. Make sure the hay you’re feeding is good quality, and weigh it to ensure that you are feeding the correct amount (we recommend 1.5% of her body weight). The alfalfa cubes can be included in that 1.5%. If this horse does not chew hay well, this amount may be difficult to get the horse to eat. That is why the senior feed and beet pulp are beneficial high-fiber additions to the diet.
Look for feeding instructions on the bag or tag of the senior feed, and weigh the amount you give your mare daily, to ensure you’re feeding according to directions. Some senior feeds are designed to be fed at a high intake rate; for example, you may see a recommendation of 10-18 lb/day (4.5-8.2 kg) for an average horse’s maintenance diet. If the horse is in work, the amount you need to feed in order to meet her requirements increases. If you aren’t following the bag’s feeding directions and feeding under the recommended amount, you might consider increasing the amount to at least the minimum.
Beet pulp is another highly digestible fiber source that is commonly used to get weight on a horse. However, to feed it safely to an aged horse it needs to be soaked, which will add a lot of weight and bulk, and decrease the energy density. So, to assure that you are supplying significant calories with this, it would be advisable to weigh the beet pulp dry before soaking. If you are not feeding more than 1 lb (0.5 kg) per day, it is not adding very many calories.
Fat is calorie-dense and a good addition to the weight-challenged horse’s diet. The more you feed, the more calories you will supply, but there is a limit to what is good for the digestive tract. For the oil, 0.5 to 2 cups per day is a reasonable amount. For the rice bran, up to 2 lb (0.9 kg) per day can be fed safely without interfering with microbial function of the hindgut.