Ask the Vet

Cattle Supplement Decisions and Data

Supplements are best used where lower quality hay or forages call for it. (Photo courtesy of Texas AgriLife)


We farm in southern Virginia. What is your opinion about protein tubs, specifically for us the 24% protein tubs? Our hay this year was late being cut, and our cows started calving in March.


First, let's look at why cows can primarily live off a forage diet. The rumen is what makes cattle, sheep and goats different from simple-stomach animals like humans and pigs. Microorganisms in the rumen break down fiber in forages that simple-stomach animals cannot utilize. The breakdown process produces volatile fatty acids that ruminants capture and utilize nutritionally.

Now let's look at the concept behind tubs and liquid feeds. Some forages do not have enough readily available nutrients to feed the rumen. This is where tubs and liquid feeds come in.

Most of these supplements contain energy sources and a combination of both natural proteins and non-protein nitrogen (NPN) or urea. The microorganisms in the rumen can use this energy and natural protein to digest the fiber in forages, turning that into carbohydrates or energy for their growth. Not only can they take nondigestible carbohydrates (fiber) and use them for energy, but they can hook NPN onto carbohydrate molecules to make proteins. This digestive process not only extracts more energy and proteins from the forage, but it does it faster so forages "pass through" the cow quicker, which allows them to eat more forage.

There are many forms and formulations of tubs and liquid feeds. Cost is not a good way to judge the value of the product. Some less expensive tubs have a higher moisture content and are less nutrient-dense. Nutrient quality is often lower. Cattle may eat more of these blocks and still receive less nutrition than from the more expensive blocks or supplements.

It is important to look at how much it will cost you to feed any supplement on a per-head, per-day basis. Also, consider how cattle perform on that supplement. Often the less expensive supplement ends up costing more to feed and it leads to lower production. That has a direct effect on profitability.

Part of the profitability issue is asking yourself if the supplement is appropriate for your unique operation. I recommend getting the hay you are feeding tested, so you know its nutrient quality. Tubs and liquid feeds offer a convenient, cost-effective method of supplementation, but if your hay is very low in total digestible nutrients (TDN) and crude protein, traditional supplemental feed may be a better alternative.

If you are going to use these products, always start while cattle are still in good body condition, usually just prior to calving. The ideal is probably a body condition score (BCS) of 6 on a scale of 1 to 9. If cattle have a BCS of less than 6 (certainly if it's less than 5), traditional supplemental feed is a better way to increase body condition.

Remember, playing catch-up when it comes to body condition is always costly both in feed expenses and production decreases. In most cases, tubs and liquid feeds alone won't provide adequate nutrition for growing cattle. In my experience, I would also extend that to include the wet, 2-year-old still trying to grow, raise a calf and breed back.

In the end, the only way to really answer your question is to start with the data. Test your hay. Establish a BCS on those females, and then consider your nutritional goals and the best, most economical, way to reach them. Always remember you have a valuable resource in your herd veterinarian, as well as your Extension beef specialist.


Editor's Note: Please contact your veterinarian with questions about the health of your herd or other animals. Every operation is unique, and the information in this column does not pertain to all situations. This is not intended as medical advice but is purely for informational purposes.

Write Dr. Ken McMillan at Ask the Vet, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email