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The Current Environment Demands Efficiency, So How Are You Doing Feeding Your Cows?

By Casey McMurphy

There are a lot of tools out there that can help you with your operation. However, there is one in particular that may come in very handy this winter when feeding your cows. The OSU Cow-Culator is a very practical calculator that is available to anyone at The website provides detailed instructions on how to use the program as well as an example evaluation.

The first picture below is a snap shot of the balance worksheet. A few notes on this page. First, it is important that you know what your performance goals are for your cows. If you have your cows in good body condition going into winter then it would be most economical to maintain this condition or even allow for a minor loss in body condition score (BCS) over the feeding period. The main thing is making sure your cows will be in a 5.0 BCS or higher on average to ensure that conception rates are not impacted. The second thing is to note that the protein ratio should be a 1.0 or higher, but the optimum is closer to one. Cows will excrete excess protein so you are losing money by over feeding protein. The final component is the Calcium to Phosphorus ratio. The ideal ratio is 2:1 (Calcium:Phosphorus). This is not an exact science but it is critical to make sure that you have enough calcium in the diet. It is a common mistake in today’s environment with the use of co-products that are high in Phosphorus and low in Calcium. These are major minerals and you will see a reduction in performance if you do not have enough calcium in the diet.

For example, I was at an operation and the producer told me that when he let the cattle out of the dry lot they started eating dirt and was curious if I had any idea why. I knew his diet consisted of silage and distillers grains and I asked if there was a lot of limestone in the soil. His response was yes and after evaluating his diet I found that not only was his Calcium to Phosphorus ratio out of line, but his diet was all together deficient in Calcium for that class of cattle. If you do nothing else from a mineral perspective please make sure that your major minerals are in line.


Next, here is a picture of the final summary. This can be very beneficial to your program when you are trying to determine how much working capital you need for the winter feeding of your cows and more importantly how much of each commodity you need to get through the winter. I used this recently with known quantities of commodities and then worked my way backward to determine the proper ration for the producer. Lots of combinations of feedstuffs will get you to the same finish line, but if you have feedstuffs stockpiled it is important to use those resources first and therefore you can determine how many days you are going to feed your cattle and then how much feed you can provide each day to ensure that you will not have to buy any commodities or at least narrow it down to purchasing the commodity that is easiest to procure.


There are some other fundamentals that are needed to use this program. If trying to determine a supplementation program in the pasture versus a total mixed ration (TMR) in a dry lot, the first question you need to answer is whether you need to supplement with protein or energy. The simple answer to this question is that if you have adequate, available forage you need protein and if you have limited forage or you want to increase body condition scores (BCS) then you need to supplement energy. This is because if there is ample forage, providing protein will increase digestibility and intake of the forage which will increase the total dietary energy available for production. Most forage has ample energy, but the animal has to be able to breakdown the forage to get to the energy. By providing protein you are supplying the rumen microbes with nitrogen (their energy source), enabling them to replicate and breakdown the forage to get to the carbohydrates. The most common way to evaluate energy in cow diets is total digestible nutrients (TDN).

Nevertheless, the most important pieces of information needed to determine how much supplement is needed are forage crude protein (CP) and energy (TDN). Cows will consume low-quality hay at a rate of about 1.8% of their body weight on a dry matter basis (DM) without supplemental protein and approximately 2.1% of body weight when provided additional protein. You need to know hay intake to determine the absolute amount of nutrients your cows are receiving each day as demonstrated in the table below.

The other information you must know are the nutrient requirements for your cows. The majority of cattle are going to fall in the category of needing approximately 2.0 lbs of CP and 12 and 14 lbs of TDN for dry and lactating cows, respectively. The Table demonstrates how to determine the nutrient balance of a 1300 lb, lactating cow that has a BCS of 5.5. You can see that a cow consuming a 7.0% CP, 51.0% TDN forage will not consume enough CP and TDN to meet her requirements during lactation. However, if you provide her with 4 lbs of a 20% CP, 79% TDN supplement you will exceed her CP and TDN requirements. Almost none of the feed labels actually have an energy level on them and therefore you must ask the feed supplier what this value is or use the Cow-Culator that has averages for most feedstuffs used in formulating cow diets.

Cow BW: 1300

Cow BCS: 5.5






CP (lb)

TDN (lb)

Nutrient Requirements







Estimated Hay Intake



Hay Composition



Digestibility Estimate



Nutrients from Forage



Nutrient Balance (Hay Only)






Supplemental Composition



Supplement Supplied



Nutrients from Supplement



Nutrient Balance (Hay + Supplement)




If you think this program is something you would like to use and have questions or if you have other general nutrition questions please do not hesitate to email or facebook us!


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