As we approach the mid-way point of the winter feeding season, I am sure that you have evaluated your forage situation and you have a good idea of how much hay you have available for the next couple of months.
I am asked from time to time to explain how you meet the protein and total digestible nutrients (TDN) when you are rationing your hay through the winter. Although not perfect, this will provide you with a good idea of how much feed you should supplement with your hay to meet the crude protein and TDN requirements of your beef cow.
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 crude protein for a cow in this stage of production will be around 3 pounds per cow per day. You have grass hay that checked 9% protein, 48 TDN and, due to a shortage in hay, you can only provide 10 pounds of hay per cow per day. You’re looking at additional supplementation with corn, corn gluten, soyhulls, or a complete feed such as 13% with Bovatec®. How much of each of these feeds would you need to provide to your cows to meet their nutritional demands?
The first information you need is the crude protein and TDN levels of all the feeds you are considering. The table will provide you this information:
||Crude Protein %
|13% Complete Feed
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 protein (10 pounds of hay X 9% protein = .9 pounds) and 4.8 pounds of TDN (10 pounds of hay X 48% TDN = 4.8 pounds of TDN). This will leave you 2.1 pounds short of protein 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% protein in corn = 28 pounds). This is infeasible because of the cost and problems that would come nutritionally from feeding 28 pounds of corn. You would feed less than 28 pounds of corn to meet TDN needs, but you would be short of protein. The answer to corn, if you choose this supplement, would be to provide an additional protein source such as supplement blocks, soybean meal, or cottonseed meal to meet protein requirements.
Let’s look at corn gluten. To meet the protein shortage with gluten, you would need to feed 11.6 pounds per cow per day (2.1 pounds short/.18% protein in gluten = 11.6 pounds per cow per day). This would also provide 8.35 pounds of TDN (11.6 pounds of gluten X .72%TDN in gluten = 8.35 pounds). In this example, a producer could easily feed 11.6 pounds of gluten, with 10 pounds of hay to meet the crude protein and TDN requirements of the beef cow at a cost that will not break the bank.
Let’s now consider soyhulls as a supplement. To meet the protein shortage with soyhulls, you would need to feed 22 pounds of soyhulls per cow (2.1 pounds short/.095%protein in soyhulls = 22.1 pounds). Fed at that rate you would see nutritional disorders such as 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 that rate. If you chose soyhulls to supplement your hay, you would need to consider an additional protein source so that you could feed less of the hulls.
The final example we will consider is 13% with Bovatec®. To meet the protein shortage, you would need to feed 16 pounds of 13% Cattle Feed (2.1 pounds short/.135%protein in 13% = 16). This will also provide you with 10.88 pounds of TDN (16 pounds X .68% TDN = 10.88 pounds of TDN). Also, with each of the above 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 these examples will show you some of the considerations that must be taken into account before selecting a supplemental feed. You must consider the total cost of our program as well as considering the practicality of the program (not practical to feed 22 pounds of soyhulls per day to cattle). I hope they will provide you with some food for thought as we enter the last 45 days of the winter feeding season.
Jimmy Hughes is AFC’s animal nutritionist.