For many areas of Western Canada, the summer of 2021 has been one of the driest in recent memory. As a result, cow-calf producers have been scrambling to put together a winter feed supply. For many of these operations, cereal and pulse straws and possibly corn stover will play a major role in getting cows through the winter. Others will look to salvage crops such as canola or byproducts such as oat or soybean hulls as substitutes for normal ration ingredients. These alternative/unusual feeds can pose challenges when attempting to formulate diets for pregnant beef cows, particularly in the dead of winter. The following discussion attempts to address some of these challenges and highlight potential pitfalls one can encounter with feeding some of these alternative feeds.
First, let’s look at the challenges one faces with straw-based diets. Cereal straw can be used to stretch hay or silage supplies or as the sole forage source in wintering beef cow rations. The key to its use is an understanding of its nutritional value, particularly relative to more commonly used feed ingredients. For example, a good quality alfalfa/brome hay might average 14 per cent crude protein (CP) and 60 per cent total digestible nutrients (TDN). In contrast, wheat or barley straw will typically average four to five per cent CP and 35 to 40 per cent TDN. Pulse straw, while somewhat higher in both nutrients, is also more variable, particularly in CP content.
While the alfalfa/brome hay cited above when fed to appetite will meet the majority of a wintering beef cow’s nutritional needs, regardless of the stage of pregnancy, straw-based diets are likely to be deficient in both energy and protein. Supplementation with more nutrient-dense feeds (i.e. barley/corn grain, canola meal, etc.) will be necessary, particularly as the stage of pregnancy advances and during periods of cold stress.
Another potential issue with feeding high levels of straw is rumen impaction. This condition results from the fact that straw is poorly digested in the rumen. When a cow eats too much straw, passage of feed through the forestomachs can slow to the point that nothing moves (i.e. cows are impacted). A rule of thumb that I use when formulating straw-based diets is to limit straw intake to 1.25 to 1.5 per cent of body weight or 18 to 21 pounds of straw per day for a 1,400-pound cow. Keep in mind that depending on stage of pregnancy and environmental stress, feeding this much straw can require supplementation of 10 to 12 pounds of barley grain or its equivalent to meet energy requirements.
Some producers had the opportunity to salvage canola as either silage or hay. When cut early (late flowering through mid-podding stage of plant growth), canola forage can make good-quality hay or silage, similar in nutrient content to the alfalfa/grass hay cited above. Inherently high sulphur levels, particularly when consumed over an extended period, can pose issues with trace mineral availability as well as potential sulphur toxicity issues. Nitrates can also be an issue in drought-stressed plants. A rule of thumb used by some nutritionists is to limit the amount of canola hay or silage to 50 per cent of total feed intake (DM basis) to minimize these issues.
Corn stover is the residual plant material following grain harvest. Its energy value depends to a large degree on the extent of grain kernels and/or cobs left behind by the combine. For cows in early to mid-gestation, corn stover can be an adequate energy source; however, protein supplementation may be required.
Oat hulls are a byproduct of the oat-processing sector. Typically, oat hulls are higher in energy (i.e. 45 to 50 per cent TDN) and protein (i.e. 4.5 to 5.5 per cent CP) than cereal straw. Nevertheless, oat hull-based diets will require supplementation with an energy/protein source if the animal’s nutrient needs are to be met. Similar to oat hulls, soybean hulls are a byproduct of soybean processing. However, soybean hulls are higher in energy (i.e. up to 77 per cent TDN depending on processing plant) and crude protein (10 to 13 per cent) than oat hulls and are an excellent supplemental feed for cattle fed low- to medium-quality forages.
Finally, screenings from the grain and pulse cleaning sectors can be used to supplement energy and protein deficient forage sources. The energy content of raw grain screenings, however, tends to be quite variable (i.e. 60 to 67 per cent TDN) depending on whole weed seed contamination and the degree of shrunken/broken grain kernels. Crude protein content typically averages 13 to 15 per cent. Processed grain screenings (i.e. ground and pelleted) have a higher energy content (i.e. 67 to 74 per cent TDN) than raw screenings while fortified grain screenings (supplemented with energy, minerals and vitamins) approach cereals such as oat and light barley in terms of energy content.
To summarize, whatever approach you take to feeding cows this winter, the key will be matching requirements with an appropriate quantity and quality of feed. To accomplish this task economically, it is essential that you have your forage and byproduct feed sources analyzed at an accredited feed testing laboratory. If you are unsure how to use the results, talk with your feed company or seek the advice of a nutritionist.
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