Supplementing cattle on dormant pastures during the fall and winter

Feb 3, 2012

Many producers in North Dakota and Montana will graze cows on dormant native range during the fall and early winter months. A sound supplementation program that meets the nutritional requirements of the cows is necessary to make these grazing programs work well.

Cattle actually have requirements for two different types of protein. The first is degradable protein, which is used by ruminal microorganisms as they digest fiber, produce volatile fatty acids and make microbial protein. The second type is metabolizable protein, which is used by the animal for maintenance and productive purposes. Microbial protein and escape protein from feeds are used to meet the metabolizable protein requirements of the animals.

A third type of protein is escape protein, which is not degraded in the rumen by the ruminal microorganisms, but is digested in the small intestine of the animal.

Cattle do not have a specific requirement for escape protein. In some cases, supplemental escape protein may be necessary because microbial protein is not adequate to meet the requirements for metabolizable protein.

Dry, gestating cows grazing dormant pastures usually require supplemental degradable protein in order for the ruminal microbes to convert fiber into energy that the cow can use and to produce microbial protein. When degradable protein is lacking in the diet, forage intake and digestibility are reduced.

On native pastures, forage quality declines during the early fall months as grasses go into dormancy. Based on diet samples collected in southwest North Dakota and southeast Montana, crude protein levels can fall to around 6 percent by November. Many studies have demonstrated positive responses to supplemental protein during this time period.

Many sources of degradable protein are available.

Soybean meal, sunflower meal, canola meal, safflower meal, wheat midds, and alfalfa contain high proportions of degradable protein (as a percentage of the total crude protein). Producers can also use urea to supply a portion of the degradable protein, but it should not be the sole source of degradable protein for cattle grazing dormant native range.

Based on requirements for degradable protein, producers should supply between 0.33 and 0.4 pounds of supplemental degradable protein per head per day. This amounts to about 1.6 to 1.7 pounds of an all natural 32 percent CP cake or 3.5 to 4 pounds of alfalfa hay per head per day.

Protein supplements do not need to be fed daily. In fact, research has demonstrated that performance is not affected by feeding protein supplements every other day, every third day, or, in some cases, once every week. This is not true with grain-based energy supplements, which should be fed every day for best results.

Also consider cow behavior when designing a supplementation program. Every herd tends to have “boss” cows or very aggressive cows who get more than their fair share of supplement. By providing supplement every other day or every third day, more timid cows have a chance to get their share of supplement. Young cows (2and 3-year-olds) are lighter and tend to be less aggressive than older, mature cows. They should be fed and pastured separately if possible.

Protein supplements will not work properly if forage quantity is limited. If it is, supply supplemental energy. Don’t expect cows to gain body condition while grazing dormant forages, even when properly supplemented. In most years, cows will maintain condition under these management conditions. Therefore, it is important that cows be in good condition (BCS 5 or greater) when these programs are started. Thin cows will not do well under winter grazing conditions because they lack the insulating fat cover of cows in better condition. Weaning earlier is one way to allow cows to maintain condition and go into the winter in better shape.

A good supplementation program will provide supplemental nutrients needed to make the most of dormant forages at a cost-effective price. — Dr. Greg Lardy, Extension Beef Specialist, North Dakota State University