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Concerns with feeding off-grade grain

Nutrition with John McKinnon, beef cattle nutritionist

In the September issue of Cattlemen, the title of my column was “Another crazy year for growing hay.” In that column I looked at some of the trials and tribulations that hay producers faced this past summer. Looking at this year’s harvest, you can’t blame grain producers for thinking that a similar dark cloud hangs over their heads! Not only has harvest dragged on longer than normal, but wet growing and harvest conditions, particularly in Western Canada, have combined to downgrade much of the crop. While no one wants to see a sector of the industry face undue hardship, there is no doubt that these conditions have resulted in a significant feed grain supply, particularly off-grade grain and, as a result, lower feed grain prices.

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For cattle feeders lower feed prices are welcome, particularly after the negative margins of the last 12 months or so. However, there are a number of challenges when it comes to incorporating off-grade feed grains into a cattle feeding program. These challenges fall under three broad categories including issues with reduced feeding value; feeding management; and with mycotoxins.

From a feeding perspective, the concern with light-weight grain is that the kernel has not filled and thus its starch/energy content is reduced. For example, normal feed wheat has a test weight of 60 pounds per bushel. In terms of net energy content, wheat has an average value of 2.2 and 1.59 Mcal per kilogram of dry matter (DM) for maintenance (NEm) and gain (NEg), respectively. Its NEg value is approximately eight per cent higher than that of barley and two per cent lower than corn grain. Feed wheat typically weighs in at less than 60 pounds (i.e. 50 to 56 pounds or less) with an energy value similar to or slightly higher than barley grain, depending on the reason for downgrading. Most feedlots consider normal barley to weigh in at 48 pounds or more. While lightweight barley is typically purchased at a discount relative to the value of normal barley, performance is not adversely affected, until bushel weight drops below 44 pounds.

Similar comments apply to corn. For example, research at the University of Nebraska has shown that there was no difference in performance of cattle fed 46-pound versus 56-pound corn.

Feed wheat offers particular challenges when it comes to feeding management. At 60 to 65 per cent starch, wheat is intermediate to barley (55 to 60 per cent) and corn (65 to 70 per cent). However, of the three, wheat has the fastest rate of rumen starch fermentation. This characteristic has important implications for feeding management as its high starch content and rapid fermentation can predispose cattle to rumen acidosis (i.e. gain overload).

Too much wheat, too quickly will result in rapid production and accumulation of acid in the rumen. This drops rumen pH and leads to acidosis which can range in severity from acute to sub-acute. Symptoms of sub-acute acidosis include erratic feed intake, reduced gains, poor conversions, lameness and liver abscesses. To minimize these issues, many nutritionists recommend blending wheat into the ration and have an upper limit on the amount fed, typically 50 per cent of the grain portion of the ration.

In a finishing diet, this means a maximum of 40 to 45 per cent wheat (DM basis). Wheat should also be introduced in steps, replacing barley (or corn) at 10 per cent increments (DM basis). At each step, cattle should be given two to three days to adapt, after which, if they are eating normally, it is safe to move to the next step. Properly adapted wheat-fed cattle will have superior feed conversions relative to barley-fed cattle, and if wheat is priced competitively, lower feed costs.

From the phone calls that I have received, the biggest issue with this year’s grain crop is mycotoxins, particularly with fusarium-contaminated grain. Fusarium infection of wheat results in shrunken, off-colour kernels, known as fusarium damaged kernels (FDK) or more commonly “tombstones.” In corn, it is sometimes referred to as pink ear rot. Fusarium-damaged kernels can be contaminated with a number of mycotoxins including deoxynivalenol (DON), nivalenol, T-2 and HT-2 toxins. While space limits the discussion of these mycotoxins, producers should be aware that toxins such as T-2 and HT-2 are extremely toxic in very small amounts. DON, while not as toxic to cattle as T-2 or HT-2 toxins, will likely be the most common mycotoxin encountered in fusarium-contaminated grain. Reduced feed intake, poor growth and immune function are the major issues one can encounter when feeding DON-contaminated grain.

Feeding mouldy grain, particularly that infected with fusarium, is tricky as the presence of the fungus does not necessarily mean mycotoxins are present, and when mycotoxins are present, it is also possible to have more than one type contaminating the grain. As well, while there are guidelines as to the maximum inclusion level of these various mycotoxins in the ration, there is no clear consensus as to what level can be safely fed. For all these reasons, if you are planning on using fusarium-contaminated grain, you would be well advised to have representative samples tested for mycotoxins by a qualified laboratory. As well, working with a nutritionist experienced with these and other off-quality grains will be critical to feeding cattle safely and efficiently.

About the author

Contributor

John McKinnon is a Professor Emeritus at the University of Saskatchewan and a consulting nutritionist who can be reached at [email protected].

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