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 Nutriti o n

By John McKinnon

Corn: The New Kid on the Block?

W

hile Quebec, Ontario and southern Manitoba have long been Canada’s focal points for corn grain production, you can’t help but notice as you drive around Western Canada that we are starting to see more and more grain and livestock producers focus on corn whether it is for grain, silage or stockpiled forage for winter grazing. This trend may snowball as the major seed developers put more emphasis on corn variety development for Canadian growing conditions. From a nutrition perspective, corn is a very versatile crop, particularly for cattle feed. Compared to barley there are several important differences when used as a feed grain. First, barley grain has an outer hull which corn does not. As a result, processing requirements differ between the two grains. Barley is typically dry or temper rolled prior to feeding to allow for optimum nutrient utilization. Corn grain in contrast can be fed whole, dry rolled, tempered or as is common in certain areas of the United Sates, steam flaked. Surprisingly, from a performance perspective it is hard to show a difference between cattle fed dry rolled barley versus dry rolled corn, although more intensive processing of corn (i.e. steam flaking) results in more efficient gains relative to barley. From a nutrient perspective, corn has a higher starch and lower fibre content, which results in a higher energy content — 88 versus 82 per cent Total Digestible Nutrients (TDN) DM basis — for corn relative to barley grain. In contrast, corn contains less crude protein (CP) than barley grain, 10 versus 12.5 per cent on a DM basis. Another important difference is that starch and protein degradation in the rumen is slower with corn than with barley. This leads to higher rumen bypass of both nutrients in corn-fed cattle. This has implications for bunk management as well as for protein supplementation. For example, while acidosis and digestive upsets are still issues for corn-fed cattle, they are not as great a problem as with barley. The relatively low protein content of corn means that corn-based finishing rations typically need some form of protein supplementation. Rumen degradable protein supplements such as canola meal or urea-based supplements are ideal, as they complement the high bypass nature of corn protein. To date most of the corn feeding in Western Canada has been in the finishing feedlot and has simply been a matter of economics with American corn replacing barley when pricing and supply dictate. In contrast, the use of corn in the forage program either as silage or as whole plant standing corn offers more immediate opportunities for beef producers. The development of lower corn heat unit varieties adaptable to Western Canada has allowed a number of feeding operations to switch at least part of their silage acres to corn. As with grain corn, corn silage is typically higher in energy (i.e. 68 versus 62 per cent TDN for barley silage,

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DM basis) but lower in protein (nine versus 12 per cent, DM basis). Its relatively low protein content usually means that protein supplementation is a requirement for most corn silage-based diets for growing and finishing cattle. In addition to its nutritional value, a major benefit of corn silage is its superior yield potential relative to barley silage under both irrigation and dryland conditions. The use of whole plant standing corn for winter grazing of the cow herd is a unique use of corn that is gaining momentum with cow-calf producers. In 2011, at the Western Beef Development Centre Ranch at Lanigan, Saskatchewan, dry matter yields of five corn varieties grown for winter grazing ranged from 4.0 to 5.7 tonnes per acre with an average energy and protein content of 62.5 per cent TDN and 8.3 per cent P (WBDC Fact sheet #2012.03). In a five-year winter corn-grazing trial at Ste. Rose, Manitoba, calculated cow days per acre averaged 250 while calculated grazing costs ($/hd./day) ranged from $0.59 to $1.09 (Manitoba Agriculture). These applied research trials show that standing corn for winter grazing can be a cost-effective alternative to traditional cow wintering programs.

John McKinnon is a beef cattle nutritionist at the University of Saskatchewan

Grain corn has higher energy content and lower fibre content than barley

However, for those considering corn a word of caution. One cannot overemphasize the importance of correct variety selection. Specifically, a variety selected for the corn heat units for your growing area. Corn is highly dependent on appropriate growing conditions (i.e. temperature and moisture) in order to achieve its yield potential. Lack of heat and/or moisture will not only reduce dry matter yield of the crop but also nutritional value due to immature plant development at ensiling or prior to a killing frost in the case of whole plant corn. In such situations, it will be hard to recover the higher cost of seeding corn. As mentioned above, western Canadian producer interest in growing corn has attracted the attention of the major seed development companies. Monsanto Canada for example has recently announced a 10-year, $100-million research program targeted at developing earlymaturing corn hybrids adapted to western Canadian agronomic conditions. Considering the genetic progress in corn breeding over the last quarter-century, one gets the feeling this is only the beginning of the story! c

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