One of the questions I get from beef producers relates to the relative feeding value of the various feed grains. Typically this question has focused on barley, wheat and oat grain. However, increasingly producers are asking how corn grain compares as both an energy and protein source. While to some this may seem like a no-brainer, there are subtle differences between these grains that can dramatically influence feeding value. With this column, I will try to highlight some of these differences and point out feeding scenarios which best suit each of these feed grains.
Let’s first look at nutrient composition. If we look at energy content, the four grains are usually ranked in the order of corn, wheat, barley and oat, with corn having the highest energy value due to its low fibre and high starch content. Barley and oat grain both have an outer hull which contributes to their fibrous nature and lower energy content.
Providing exact energy values is difficult, as values are not only influenced by variety and growing conditions, but also the type and degree of processing employed. For example, dry rolled corn and wheat are fairly similar in Total Digestible Nutrient Content (TDN) at 87 to 88 per cent and in their net energy of gain (NEg) content (1.49 Mcal per kilogram). Respective values for dry rolled barley are 83 per cent TDN and 1.37 Mcal of NEg, while for oat, the typical TDN value ranges from 76 to 78 per cent with a NEg of 1.21 Mcal. However, if corn is processed more extensively (i.e. steam flaking) or harvested as high moisture grain, energy values are significantly higher (i.e. TDN values can reach 90 or 95 per cent, respectively).
If we look at crude protein content, the picture changes. Wheat typically has the highest protein content of the four grains at 13 to 15 per cent, with corn at the low end (eight to 10 per cent). Barley and oat grain tend to have intermediate values (11 to 13 per cent). In addition to differences in the amount of protein, there are also differences in rumen degradability of the protein. Corn protein is more resistant to rumen digestion than that of the other cereal grains and as a result has a higher rumen undegradable protein content. This can influence decisions on protein supplementation. For example, with corn-based finishing rations urea-based protein supplements can be used to meet requirements at a lower cost.
Low calcium content is a common characteristic of all feed grains, particularly when compared to the animal’s requirement for this mineral. Close attention to the calcium content of the total mixed ration is needed to prevent a calcium deficiency when high grain rations are fed.
Some of you might wonder how field peas compare. If we look at energy content, peas are similar to dry rolled corn or wheat at 87 to 88 per cent TDN (1.49 Mcal NEg) but are superior in CP at 22 to 24 per cent, the vast majority of which is rumen degradable. Research from North Dakota State University has shown that when peas are included at levels up to 30 per cent of the diet DM, they can support comparable or even superior performance relative to barley or corn-based diets.
As discussed above, processing becomes a critical factor to consider when comparing the relative feeding value of cereal and pulse grains. Dry rolling is still the most common method used to process barley and wheat. With barley one needs to break open the hull and seed coat, while with wheat the outer seed coat needs to be cracked. Ideally, rolling results in breaking the kernel into two to three pieces without creating excess fines. A similar recommendation would apply to dry rolling corn grain. Corn grain can also be fed whole with acceptable results, although performance is typically improved with processing. Maximum corn energy values are obtained with steam flaking, which increases starch digestibility. However, this requires a specialized mill.
Oat grain can also be fed whole, particularly to younger cattle (i.e. less than 650 pounds). With heavier cattle, processing is likely required to get maximum value out of the grain. Peas also require processing for optimal use. However, efficient digestion can be achieved by just cracking or breaking the pea grain in two.
It is also important to realize that there are differences between these cereal grains in the nature of the starch and its rate of digestion in the rumen. With barley, wheat and oat grain, as long as rumen bacteria have access to the interior of the kernel through proper processing, the starch within the kernel will be rapidly digested. This rapid rate of digestion can lead to issues with digestive upsets (i.e. acidosis) if the feeding program is not properly managed. As with protein, corn has higher levels of rumen undegradable starch, particularly when fed whole or dry rolled. While acidosis can still occur on corn-based diets, there is not the same degree of concern as with barley- or wheat-based diets.
Understanding the above differences in nutritive value is an important first step when choosing which feed grain is best suited to your operation. However, factors such as relative pricing, supply and storage considerations (i.e. high moisture corn or barley) also need to be taken into account, in order to ensure a consistent, competitive feeding program.