Straw is Economical Winter Feed

EDMONTON - Nov 18/04 - SNS -- Despite its low energy and poorer digestibility than hay or greenfeed, straw can be an economical addition to winter feed for cattle.

"Generally, a cow can consume 1.25% of her body weight in straw dry matter (DM)," says Juanita Kopp, forage/beef specialist with Alberta Agriculture, Food and Rural Development's Ag-Info Centre, Stettler. "A 1400 pound cow could consume 17.5 pounds of straw on a DM basis, or 19.9 pounds on an `as-fed' basis if the straw was 90% DM.

"Near the end of gestation, the capacity of the rumen is reduced by about 12 to 13% because the growing calf takes up internal space. Straw-based rations should not be fed at this time and they should not be fed once the cow has started to lactate, save your best quality feed for this time."

In order of preference, cattle will eat oat straw before barley straw, followed by legume straws, and wheat straw. The quality of legume straw can be extremely variable. The more leaves that are on the stems the better, but it can be very coarse and of poor quality. Coarse stems are also harder to dry down so mould growth may be present.

"Cattle prefer straw that has aged a year or more, it is slightly more palatable and digestible," adds Kopp. "Processing does not improve quality but can increase the daily straw intake. However, to prevent malnutrition, impaction, poor conception rates and lower milk production, you need to supply adequate amounts of energy, protein, minerals and vitamins. It's important to know the nutrition values of the straw you are feeding."

Treating straw with anhydrous ammonia is one way to improve its crude protein content and digestibility. In a study conducted by Manitoba Agriculture and Food, the crude protein content of barley straw went from 5.1 to 9.4% crude protein when anhydrous ammonia was applied at 3.0% of the forage dry matter.

              Nutrient Composition of Various Straws

           Protein    Digestible  Calcuim   Phosphorous  Potassium
           (CP, %)    Nutrients   (Ca, %)     (P,%)       (K, %)
                       (TDN, %)

Oat           4.4        45        0.23        0.06        2.53
Barley        4.4        40        0.3         0.07        2.37
Wheat         3.5        41        0.17        0.05        1.41
Pea           6.4        46        0.6         0.19        2.04
Canola        3.9        41.5      0.29        0.18         0.8
Lentil        6.4        46        0.65        0.2           -

"Since protein and energy available in straw are not adequate, there are a number of protein and energy supplements that can be used," says Kopp. "Provide a good energy source such as cereal grains or good quality pellets or cubes. Protein can be supplemented by feeding canola meal, soybean meal or beef protein supplements. If you decide to use pellets, request the nutrient analysis including both the protein and energy values of the product."

Impaction can be a problem that occurs when feeding straw-based rations. When the weather turns cold, cattle will try to keep warm by increasing their feed intake. Since straw is not easily digested, it does not pass quickly enough through the animal and they can become impacted. Impaction can result in the death of the animal, so care must be taken to balance rations correctly, especially during the colder winter months.

Another problem involved mineral uptake: straw and grain are high in potassium (K). A ration high in K can cause a magnesium deficiency that can result in winter tetany, a condition similar to grass tetany or milk fever. Limestone or magnesium oxide should be added to the ration to prevent this deficiency.