January 2008
Feeding Facts



2007 is over along with drought, reduced hay crops, increased fuel, feed and fertilizer costs, but average cattle prices. As we look to 2008, we hope to find a year with adequate moisture, good crops, fair prices and increased productivity.

As we approach the beginning of a new year, as well as the beginning of winter feeding season, I am sure you have evaluated your forage situation and have a good idea of how much hay will be available over the next couple of months.

I am asked from time to time to explain how to meet the crude protein (CP) and total digestible nutrients (TDN) requirements of your cattle while rationing the hay through the winter. Although not perfect, this will provide you a good idea of how much feed you should supplement with your hay to meet these requirements.

At the current time, most producers have cows with calves or are about to start a spring-calving season. The TDN requirement for a cow nursing a calf is 12 pounds of TDN per cow per day. The requirement for CP for a cow in this stage of production will be around three pounds per cow per day.

You have grass hay checked at 9 percent CP, 48 percent TDN. Due to a shortage in hay, you can provide 10 pounds of hay per cow per day. You’re looking at supplementing with corn, corn gluten, soyhulls or a complete feed like 13% with Bovatec. How much of each of these feeds is needed to provide the nutritional demands the hay cannot meet?

The first information needed is the CP and TDN levels of all the feeds being considered. The table below left  will provide this information:

Ingredient Crude Protein % TDN%
Hay 9% 48%
Corn 7.5% 80%
Corn Gluten 18% 72%
Soyhulls 9.5% 65%
13% Complete Feed 13% 68%


We can now determine the feed needs of your cows. As I stated earlier, due to hay shortage you could only feed 10 pounds of hay. This 10 pounds of hay will provide you .9 pounds of CP (10 pounds of hay X 9% CP = .9 pounds) and 4.8 pounds of TDN (10 pounds of hay X 48% TDN = 4.8 pounds). This will leave you 2.1 pounds short of CP and 7.2 pounds short of TDN.

To meet the protein shortage with corn, you would have to feed 28 pounds per cow per day (2.1 pounds short/.075% CP = 28 pounds). This is infeasible because of the cost and nutritional problems caused from feeding 28 pounds of corn. You would feed less than 28 pounds of corn to meet TDN needs, but it would be short of CP. If you choose to supplement with corn, the answer would be to provide an additional protein source like supplement blocks, soybean meal or cottonseed meal to meet protein requirements.

Let’s assume you are looking at corn gluten. To meet the protein shortage, you would feed 11.6 pounds per cow per day (2.1 pounds short/.18% CP = 11.6 pounds). This amount would also provide 8.35 pounds of TDN (11.6 pounds X .72% TDN = 8.35 pounds). In this example, a producer could easily feed 11.6 pounds of gluten with 10 pounds of hay to meet the CP and TDN requirements at a cost that will not break the bank.

Let’s now consider soyhulls as a supplement. To meet the CP shortage, you would need to feed 22 pounds of soyhulls per cow (2.1 pounds short/.095% CP = 22.1 pounds). Fed at this rate, you would see nutritional disorders like milk fever and bloat. While 22 pounds of soyhulls will more than meet the TDN requirement of your herd, it is unpractical to feed soyhulls at this rate. If you chose soyhulls to supplement your hay, you would need to consider an additional CP source so you could feed less hulls.

The final example we will consider is 13% with Bovatec. To meet the CP shortage, you would need to feed 16 pounds of 13% Cattle Feed (2.1 pounds short/.135% CP = 16). This 16 pounds will also provide 10.88 pounds of TDN (16 pounds X .68% TDN = 10.88 pounds).

Also, with each of the previous examples, you would need to provide a free choice complete mineral. The complete cattle feed will meet the mineral needs of your cattle, but it is always a good idea to provide minerals on a free choice basis.

I hope through these examples you can see some of the considerations to be taken into account before selecting a supplemental feed. You must consider the total cost of your program as well as considering the practicality of the program (it’s not practical to feed 22 pounds of soyhulls per day). I hope these examples will provide some food for thought as we enter the last 45 days of winter feeding season.

If you are short on hay and would like for me to look at your feeding situation to determine your best options, please feel free to call me at 256-947-7886 or e-mail me at This email address is being protected from spambots. You need JavaScript enabled to view it..

Jimmy Hughes is AFC’s animal nutritionist.