Alberta and Saskat-chewan still grow millions of acres of barley, but Manitoba broke a 30-year-old record in 2012 by planting 300,000 acres of harvested grain corn, which easily surpassed the previous high of 225,000 acres in 1981.
On a Prairie-wide basis, barley is still the major feed grain crop with about 6.3-million acre harvested in 2012. However Manitoba planted only 490,000 acres of barley last year, down considerably from a high of about 2.5 million acres of barley in 1981. In Manitoba and to a lesser extent in other provinces, corn is becoming a viable option as a cash crop and a livestock feed.
Along with that, many dairy producers on the Prairies have replaced barley with corn as the sole grain in their cows’ lactation rations. Recent spikes in corn prices on the cash and futures market as well as more economical barley has not reversed the trend, showing that corn is unlikely to be removed from high milk-producing diets anytime soon.
CORN HAS A FIT
That’s because good-quality corn has a high starch content, which permits the formulation of higher energy-dense dairy rations, particularly needed during a period of early lactation in dairy cows. At this time dairy cows are most likely to suffer from a period of “negative energy balance.” There’s a lag time of five to six weeks between the heavy demands of energy for milk production and the lack of dietary energy intake in even the best dairy feeding program.
To survive this natural energy crisis, the cow mobilizes and breaks down her own body fat, which supplies a substantial amount of energy to support milk production. This often leads to serious metabolic diseases such as ketosis or fatty liver syndrome. However, a corn-based dairy diet can help minimize excessive fat breakdown,
Not only does a corn kernel contain a high level of starch (72 per cent), but the natural digestibility of cornstarch in dairy diets seems to be more time-controlled than in cereal grains such as barley.
A kernel of cornstarch is uniquely embedded in a highly resistant protein matrix, which repels microbial invasion. What bacterial degradation that does take place to cornstarch is slow. A significant portion is forced into the small intestine for final digestion. In addition, as grain corn dries (to less than 15 per cent moisture), its starch forms a crystalline structure that is even more difficult for the rumen microbes to degrade rapidly.
Some dairy specialists have viewed this relatively slow degradation of cornstarch in the cows’ rumen as a nutritional obstacle in supplying large amounts of readily available energy for better milk yields. Therefore, many physical and “cooking” techniques have been developed, which increase corn-starch’s exposure to the ruminal microbes for better fermentation and energy release. Such examples include: (i) high-moisture corn (25 per cent moist), (ii) grinding/cracking (increases surface area/breakdown of protein matrix) and (iii) steam-rolling or cornstarch gelatinization.
There are many university and field trials that illustrate the dietary benefits from each of these processes. It has been showed that high-moisture corn is quite palatable compared to dry corn and increases diet dry matter intake. In a similar fashion, fine-ground or steam-rolled corn yields eight to 10 per cent more dietary energy than regular dry corn and is backed up by some favourable production studies.
Other studies temper these positive results with a substantial threat of rumen acidosis and off-feed problems in high milk-producing dairy cows. Despite these latter adverse messages, science tends to favour processed grain corn for lactating dairy cows as long as corn moisture and particle size is optimized in order to promote healthy cornstarch digestion in the rumen and small intestines, which turns into good milk production.
No matter how the corn kernel is processed to release more dietary energy for dairy cows, it really does little to improve corn’s natural low-protein content or digestion.
Corn contains eight to nine per cent protein compared to cereal grains such as barley, wheat or millet with 11-13 per cent protein. It doesn’t concern most dairy people because of routine formulation often calls for high-protein forages such as alfalfa forage or high-protein concentrates such as canola or soybean meal. Corn protein has a bypass protein value, which is about double of cereal grains, so there is a small nutrient trade-off, especially when soluble protein is fed.
CAN BE REPLACED
As much as corn might be favored in lactation dairy diets for its high energy (starch) content (and accept it as a low-protein grain), it can be easily replaced, when its availability shrinks or its cash price skyrockets. Luckily, there are many total or partial replacements for grain corn such as barley, wheat, wheat middlings, or even bakery wastes. Ironically, some energy substitutes are derived from grain corn.
Corn distillers’ grains with solubles (DDGS) is low in starch, but is an excellent source of protein (27-30 per cent), ruminal by-pass protein (57-62 per cent), fat (10-12 per cent) and a source of highly digestible fibre; together is estimated to have a energy density of corn (Nel = 2.10 Mcal/kg). One kilo of DDGS can theoretically replace 0.6 kg of corn and 0.4 kg of soybean meal in a high milk producing diet. As a result (from sound field trial data) dairy cows fed DDGS up to 30 per cent of their dairy ration can produce comparable milk volume and maintain important milk components.
Such movement toward corn substitutions like DDGS and other replacements seem to be more imminent when corn supplies are tight and these other ingredients are more available. By comparison, when corn is expensive, the movement toward the same replacement feedstuffs is not as predictable, because the producer’s decision to feed corn is not always based upon its cost.
For example, the cash price of corn is about $7.50/bushel ($295/mt) and barley is about $5.50/bushel ($251/mt); a standard 7.0 kg of barley substituting corn strictly on a 1:1 dietary energy/starch basis would technically save about $0.31/head/day in ration costs. For a 100-dairy-cow herd, this diet translates into an approximate $11,000 annual savings in feed costs.
Dairy producers who have the favourable experience of corn as a grain ingredient, have often made it the gold standard for dairy cows, particularly on the eastern Prairies. Manitoba total grain corn acres are predicted to increase between 10-15 per cent in 2013. With the development of new corn varieties that require fewer heat units and shorter growing seasons; the movement of more corn onto traditional cereal acres, and then some of it into more westward dairy diets is very possible. †