Supplements for Cows and Steers

Find out if you need to supplement your grass hay feed.
Supplements for Cows and Steers - Articles


We often get the question from beef producers, "I am feeding grass hay to my cows, so what should I supplement them with?" The answer is not easy.


All hay is not created equal.

If I go back through numerous hay samples I have seen on my desk from "grass hay", it is clear there is significant variation in the feed values for hay named "grass." There can be as much as 50% variation between samples for both energy and protein values in these samples. Another significant value is moisture content. While dry hay normally has a smaller range of dry matter value, consider a 5% difference in dry matter for an 800-lb bale of hay. For a cow eating 20 lbs. of hay, there will be 5% less protein and 5% less energy in every bite she takes in the wetter bale. Finally, the whole bale is not feed, even when it is stored inside. Weathering of a bale uses up nearly all the energy and most of the protein in a bale. Dry matter losses are generally 20-30% for bales stored outside, and 4% for those stored inside. Table 1 shows some nutritional values observed from "grass hay."

How much hay do they eat.

It does not matter how much hay you put in front of cow. The only thing that counts is how much of it she eats. How much of it does not get in her? Feeder design will change that value significantly. Most studies show the typical ring feeder will result in about an 8% loss, the inverted cone feeder will have about a 2% loss, and no feeder at all can result in losses up to 50%. The variation in bale weight can fool the feeder. The difference in the amount of feed that is offered in a 700-lb bale is about 12% less than that offered in an 800-lb bale. This may make little difference to the feeder who just provides more hay when the feeder is empty, but for winter feed planning purposes, when buying hay, or when hay may be in short supply it can be significant.


All cows are not created equal.

Cows do not "read the book" very well about how they are supposed to perform. In all cases, observing cows, how they are eating, and what they look like will be the most valuable management. The amount of feed a cow eats-and the basic amount of feed a cow needs-is based on their weight. The weight determines the metabolic body weight which is the amount of feed nutrients it takes to keep a cow breathing and her organs to operate. Cold weather, walking, gestation, her age, and all other variations to her environment add additional nutrients to her needs, so it can be seen "the book" is not always going to be the best description of what a cow needs.

The most important feature of winter feeding cows is their condition. We know without question the most important feature of profitability in a cow herd is weaning a live calf. The condition of a cow during the winter has a significant effect on her ability to wean a calf the next year. For example, the 3-yr old cow that just weaned her first calf is eating hay this winter that is about 10% short on energy for her needs. She goes from a condition score of 5 to just barely a 4 by March. This cow typically has a 30% chance of not getting bred for the third calf, and the milk production for her second calf will be diminished. In this day of record prices for feeder cattle, the losses are costly.

Table 1. Variation in nutritional value for "grass" hay
Hay sourceNEm1TDN %Crude protein %
Grass hay #1595911
Grass hay #2555410
Grass hay #3525010
Grass hay #448487.5

1Net energy of maintenance (megacalories per 100 lbs.).

Table 2. Comparing nutritional needs for the "typical" cow with different hay. Requirements for a 1200-lb cow1
Hay sourceNEm2TDN %3Crude protein %
Grass hay #1-
Grass hay #2-
Grass hay #3-6.2-0.10.6
Grass hay #4-7.0-0.50.1

1Mature cow in the middle 1/3 of pregnancy.
2 Value= Nutrient from hay minus nutrient supplied in 20 lbs. daily intake of hay; NEm=net energy of maintenance (megacalories).
3Total digestible nutrients.


The results in Table 2 highlight the type of supplementation usually needed in a cow herd. For mature cows, protein will seldom be the deficient nutrient, while energy often will be needed. Younger cows (2-3 years old) will have a protein requirement that is 15-20% higher.

Energy can be supplied in a number of ways. Generally the cheapest source of energy is corn. With a typical NEm value of 98 Mcal/cwt, the deficiency found with grass hay #4 (Table 2) can be solved with about 7 lbs. of corn per head daily. Any cereal grain or grain by-product can be used to provide energy, but some processing (such as with wheat) may be needed. Food by-products such as chips, chocolate, and bakery waste are also good sources. When corn is $7.00/bu. The cost per pound is $.12 or $.875 per day to supplement grass hay #4. The energy value of any substitute for corn must be known to get an equivalent price. For example, oats may cost $3.50/bu, but supply only 83% of the energy of corn. The equivalent price for oats in this case would be $.93 per day. The most expensive supplements are usually the most convenient. Blocks and lick tanks are designed for protein supplements, so the energy the cattle get from the molasses is at a high cost.

Prepared by Dr. John Comerford, former Penn State Extension Beef Specialist