Feeding Cows When Feed Supply is Limited
Livestock Update, September 2007
Dr. Mark L. Wahlberg, Extension Animal Scientist, VA Tech
A short hay crop and burned up pastures are putting the pressure on the cow manager now, and have cranked up the anxiety level for the upcoming winter season. So, there is an immediate need to deal with, and a looming big problem to plan for. It is impossible to provide "The Answer", because every producer situation is unique. But the factors to consider are really biological ground rules, so let's review what some of those are and how they relate to the situation described in the first sentence.
Rule 1. If given all they want, cows will eat until they are full. But how much feed is that? And what drives this system? When a cow is not lactating, her feed intake is primarily determined by her body size. Typical dry matter intake values reported for 1000, 1200, and 1400 pound cows are 21, 24, and 27 pounds, respectively. This is a little over 2% of her body weight. However, when they are lactating their intake goes up dramatically, and intake is even higher for cows with higher milk production potential. Because milk production peaks at around 2 months after calving, this is when the feed intake is at its highest. The same 1000, 1200, and 1400 pound cows in month 2 of lactation, producing 20 pounds of milk daily are predicted to have dry matter intakes of 25, 28, and 31 pounds. So the cow in early lactation eats 15% to 20% more feed in order to be full when compared to the same cow in mid-pregnancy.
Bottom Line - Big cows eat more feed than smaller cows, and lactating cows eat more than dry cows, when given all they can eat.
Rule 2. Cows need a certain amount of nutrition each day, not a certain amount of feed. The basic nutrients needed are energy (expressed as TDN, Digestible Energy, Net Energy, etc) and Protein (may be crude protein, digestible protein, etc). Cows need a minimum amount of nutrition each day just to stay alive - this is called their Maintenance Requirement. If they are done growing, not lactating, and are not close up to calving, then this is all the nutrition they need. However, if they are heavy in calf, the developing fetus demands additional nutrition. And if a cow is lactating, the nutritional requirement is even higher, since milk production is a nutritionally demanding phase of a cow's life.
Let's look at the same 1000, 1200, and 1400 pound cows again. During mid-pregnancy, the energy requirement (pounds of TDN) is 10, 11, and 12.5 pounds daily. In early lactation with 20 pounds of milk production, these numbers are 14.8, 16.2, and 18 pounds daily. So, the energy requirement in early lactation is 40 to 50% higher than it is during mid pregnancy for the same cow. Values for protein would show a similar trend.
As long as a cow consumes enough energy and protein each day to meet the requirement for her stage of production, she will get along just fine. If the feed is high enough in quality, she may be able to get enough energy and protein without eating until she is full. Feed quality has got to be higher for cows in early lactation when compared to cows in mid-pregnancy.
Rule 3. Grains have more energy (and often more protein, too) than do forages. TDN values for hay range from under 50% of dry matter to almost 60% dry matter. Pasture can be as high as the upper 60's. Corn, on the other hand, is right at 90% and both corn gluten feed and soy hulls have 80% TDN. Therefore, each pound of grain provides more energy than a pound of any forage. Corn grain has enough more energy that 1 pound of corn has almost as much energy as 2 pounds of medium quality hay.
Bottom Line - Grain can be an energy source for cows.
Rule 4. Cows need a minimum amount of fiber. This means that cows need to eat a certain amount of feed that provides a "scratch factor" as it moves through their digestive system. This comes from long hay and pasture grasses. Not only is chemical fiber an important factor, but so is the particle size of the fiber. This is why the highly processed byproduct feeds, such as soy hulls, don't have a good fiber effect inside the digestive tract, even though they have a high fiber level when analyzed in a feed lab.
But, it doesn't take much fiber to be enough. Lots of research has found that 1/2% of a cow's body weight is enough hay each day to provide the needed scratch factor. This is around 5 pounds per day. When you compare this value to the amount of dry feed (hay) she is able to eat that was mentioned in Rule 1, this is a pretty small amount. Realize that this amount of high fiber feed does not provide much in the way of nutrition (meaning not much energy or protein).
Rule 5. High grain feeding programs can work well for cows. By putting together the facts discussed in Rule 4 (minimum fiber) and Rule 3 (grains have high levels of nutrition) we can develop a grain-based feeding program that works. We do this by ensuring the cow gets at least 5 pounds of hay or hay equivalent each day. This can be in the form of a round bale of decent-quality grass hay, grass pasture that has enough growth to ensure adequate intake, or some other similar roughage source. Then, the proper amount of grain can be fed to provide the actual energy and protein required for the cow each day. For a dry cow this is around 10 to 15 pounds of grain each day, depending on her body weight, or right at 1% of the cow's body weight daily.
Go back to Rule 1 for a minute. Check the amount of dry feed she is able to eat if she has free access. Compare this to the amounts mentioned in the paragraph immediately above. When cows are fed limited roughage plus limited grain, they are a little hungry.
High grain feeding programs for cows should use pelleted or whole grain feeds. Cracking of corn or barley is not necessary. The larger particle size slows down the digestion rate a little bit and reduces the likelihood of digestive upset. And whole grain cost less than grain that has been processed.
Bottom Line - Limited amount of hay or pasture plus the proper amount of grain can meet the nutrient requirements for a cow.
Rule 6. Grains have high Phosphorous and low Calcium levels. The problem with this is that the cow's requirement for these two minerals is the exact opposite. Therefore, the mineral supplementation program must be modified when a high grain, limited roughage program is utilized. Basically, the cow's Phosphorous needs will be met with the grain, but the Calcium requirement will not. Additional limestone (an inexpensive source of Calcium) is useful to raise the Calcium level of the mineral mix.
Management strategies to consider in dealing with this drought-induced feed shortage must be implemented soon. In addition, a plan for winter feeding has also got to be developed. Use these key points to make the decisions.
Limit Feeding of high grain rations to dry beef cows is a proven method of reducing forage needs while at the same time meeting the nutrient requirements of cows. It can also be used successfully with lactating cows.
Below are listed two Fact Sheets that provide additional guidance on feeding high grain rations to beef cows when hay is in limited supply. The web addresses are included.
LIMIT-FEEDING COWS ON A CORN-BASED DIET. Steven C. Loerch. http://beef.osu.edu/library/limitfed.html
Limit Feeding Concentrate Diets to Beef Cows as an Alternative to Feeding Hay. David Lalman. ANSI-3028 http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2017/F-3028web.pdf