Q.I don’t ride as much during the winter as I do in the summer. To compensate for my horse’s reduced workload and prevent weight gain, I recently switched him from 4 pounds of performance feed a day to 4 pounds of a low-starch feed. Despite the switch, he’s gaining weight. Why is he gaining weight on a low-starch feed?
A.Horses that aren’t working relatively hard are unlikely to need concentrate feeds high in starch, so reducing starch is a good idea as work levels decrease. However, weight maintenance is a function of calories consumed versus calories burned. If calories consumed exceed those used the horse will gain weight. Conversely, if a horse’s caloric intake is less than the calories he uses, he will lose weight. There are many potential sources of calories in a ration other than starch, so decreasing starch intake might not decrease a horse’s overall calorie consumption.
Additionally, just because a feed says that it’s low-starch or low in nonstructural carbohydrates (NSC), that doesn’t necessarily mean that it is low in calories. In fact, performance low-starch feeds are likely to be fairly high-calorie, because their goal is to provide for performance horses’ elevated caloric needs but by using less starch.
There are multiple ways to increase a feed’s calorie content without increasing starch. For example, wheat middlings have considerably less starch than the whole grain (23% vs. 60%). Yet wheat middlings still provide about 1.5 Mcals digestible energy (DE) per pound to wheat’s 1.7 Mcal DE per pound. Wheat middlings have become increasingly popular in performance feeds where a restricted starch intake is desired but calorie intake needs to be maintained.
Fat sources are also used in some low-starch performance feeds as a way of keeping calorie intakes up and starch and sugar content low. Vegetable oil, for example, provides no starch but 2.25 times more calories per gram than an equal weight of carbohydrate. A number of feeds on the market that qualify as low-NSC feeds with a crude fat content of 10% or more and a calorie content in the region of 1.5 to 1.9 Mcals DE per pound.
Beet pulp is another common ingredient in low-starch feeds. This highly fermentable fiber is only 1% starch and about 1.2 Mcals DE per pound. This is higher than most grass hays, which typically fall in the range of 0.8 to 0.9 Mcals DE per pound.
This raises the issue of the nutritional profile of the forage you’re feeding your horse. Many owners concern themselves with lowering the NSC content of concentrate feeds that they are feeding. This is certainly an important component; however, if most of the ration is made up of a forage with relatively high NSC and overall high nutritional value, removing a limited number of grams of NSC by way of changing the concentrate will likely have a limited overall impact.
The other concern I have with your horse’s current diet is that most performance feeds have a feeding requirement that’s greater than 4 pounds per day for an average-sized horse. It’s therefore possible your horse isn’t getting all the minerals and vitamins he requires, because you aren’t feeding him according to the manufacturer’s instructions.
I recommend you consider removing the performance and/or low-starch feed all together and looking for a feed that has a smaller 1- to 2-pound per day feeding intake. These are often referred to as “ration balancers” and tend to be on the lower end of the spectrum of calorie intake (around 1 to 1.3 Mcals per pound of DE) when comparing them to other commercial feeds. Many ration balancers are also low in starch, although not always.
You might also need to consider reducing hay intake, although this is never my preference and all efforts should be made to keep hay consumption at or above 1.5% of body weight per day. This will help maintain your horse’s healthy gut function. Your horse might require a lower-nutritional-quality hay if his body condition continues to be a problem.
It summary, it’s important when purchasing commercial feeds to appreciate that the names used to describe feeds might not tell the whole picture. Looking at the guaranteed analysis levels of crude fat and fiber as well as the ingredient list will give you a better idea of whether the feed you are considering will meet your horse’s needs.