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Is your roller mill robbing cattle of nutrition and stealing your profits?

As you read this, harvest should be drawing to a close and we will soon have a handle on this winter’s feed grain supply and pricing. For those looking to feed this winter, ensuring that cattle effectively utilize the grain portion of the diet is a critical component of your management. One only needs to walk a pen to realize that poor feed processing practices result in an unacceptable level of whole kernels in the manure. These whole kernels are in effect stealing your profit, as they do not provide any nutritional value to the cattle and contribute to poor feed utilization.

Poor feed processing practices can be traced directly back to the roller mill. In most cases, the rollers are set too tight and the grain is overprocessed (i.e. too high a proportion of fines) or they are too far apart and the grain is underprocessed (too many whole kernels). Damaged rollers or those that need to be re-grooved also have a negative impact on the efficiency and quality of the rolling process.

The need to process and the degree of processing required varies depending with the type of cereal grain you are feeding. Remember that rumen microbes need access to the interior of the grain kernel if they are to efficiently ferment the starch. With grains such as barley and wheat, the outer seed coat (and hull in the case of barley) provides protection against chewing and rumen fermentation activity. When barley or wheat kernels are fed whole, a significant proportion will pass through the animal undigested. For this reason these grains need to be processed, typically by dry-rolling, although in some cases the grain is tempered before rolling. Overprocessing results in excessive production of very fine particles that can cause a variety of digestive upsets ranging from cattle going off feed to more severe issues related to sub-acute and acute acidosis.

Oat grain is also covered by a hull. Young calves will effectively utilize the whole oat; however, with older cattle, this grain needs to be dry rolled for optimal feed utilization. Corn grain is unique as the kernel does not have a hull; however, its outer seed coat is relatively easy to disrupt by chewing. For this reason, feeder cattle perform relatively efficiently when fed whole corn as the main concentrate in the ration. Corn can also be dry rolled, although the benefits over feeding whole are debatable, particularly when the cost of rolling is considered. Typically, the most efficient gains are achieved when corn is steam-flaked. The starch in steam-flaked corn is more available to rumen microbes and the result is a higher net energy value for both maintenance and gain. Cattle fed steam-flaked corn typically exhibit more efficient gains relative to those fed whole or dry-rolled corn. The benefits of steam flaking, however, need to be balanced against the increased processing cost, particularly with cereal grains such as barley or wheat.

Evaluating the efficiency of your roller mill is unfortunately not an exact science. Subjective appraisals include monitoring the feed bunk and intake of the cattle, as well as walking the pens and observing the manure. With respect to the feed bunk, one does not want to see an excessive accumulation of fines or erratic eating habits by the cattle. Visual inspection of the manure for both consistency (i.e. normal versus grey and runny manure) and relative quantity of whole kernels are also good indicators of the effectiveness of the grain processing and feeding management programs. Too many whole kernels indicate that the roller is not performing as it should. Some nutritionists and feedlots will go so far as to analyze the starch content of manure to evaluate the effectiveness of the processing program.

A more objective approach is to measure the degree to which the grain has been processed. This is commonly done in one of two ways. The first method, developed by Dr. Garry Mathison of the University of Alberta, involves measuring the proportion of fines by sieving a known amount of processed grain through a one-millimetre screen. Ideally the proportion of fines passing through the screen is less than three per cent; however, in reality, one needs to accept five per cent or slightly higher, if one wants to ensure that the vast majority of kernels are processed. A second method is to look at the processing index, which is a measure of the weight of a volume of processed grain relative to the weight of an equal volume of unprocessed grain. While values found in industry range from as low as 65 to as high as 85 per cent, it is not uncommon to see values between 75 and 80 per cent. Values below this range indicate a more aggressive feeding program and the need for close attention to proper bunk management practices, while higher values indicate a less aggressive feeding program and potential issues with poor feed efficiency.

While such attention to your roller mill may seem overboard, remember that a 10 per cent improvement in feed efficiency translates to a reduction in feed costs of $15 to $20 or more per head.

About the author


John McKinnon

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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