Chasing carcass quality not as easy as it looks

Nutrition with John McKinnon, beef cattle nutritionist

This is an interesting time of year when one looks at feedlot placements. Most of last year’s yearlings are gone, with fall-placed calves well into their feeding program. As well, many lots have tried to keep pens full by bringing in short yearlings that were backgrounded over the winter or in some cases by feeding lightweight calves that will go to grass by the end of May or early June. There may even be the odd pen of cull cows on feed. This mix illustrates the classic challenge feedlots face in taking a wide variety of cattle that vary in weight, age, sex and genetic makeup and feeding them to narrow carcass quality and weight end-points demanded by the market.

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In order to fully understand this challenge, let’s look at the definition of carcass quality which in today’s marketplace with natural, organic and numerous branded programs is getting more difficult to define. If we restrict ourselves to the vast majority of conventionally fed cattle, the quality and yield grades of the Canadian or in the case of our southern neighbour, the U.S. Department of Agriculture’s beef-grading regulations are the gold standard. Canadian quality grades are only applied to youthful cattle and are based on marbling. They range from Canada Prime (slightly abundant or better marbling) to AAA (small or better marbling) to AA (slight or better marbling) to A (trace marbling). Respective USDA quality grades are Prime, Choice, Select and Standard. Canadian yield grades (YG) reflect the per cent lean meat in the carcass and attempt to classify carcasses based on fat content with overfat carcasses often discounted by the market. There are three Canadian YG that are based on measurements of the subcutaneous fat thickness and muscle area of the rib-eye. These include Canada 1 (59 per cent or greater lean), Canada 2 (54 per cent to 58 per cent lean) and Canada 3 (less than 54 per cent lean). USDA yield grades range from 1 to 5 and while assessed somewhat differently than Canada’s, they effectively classify carcasses from leanest (USDA YG 1) to fattest (USDA YG 5).

The challenge is to target the right combination of quality and yield grade that the market wants. Of course, this is a moving target depending on packer, local market or in some cases branded programs. Although not always the case, carcasses with higher marbling (i.e. Canada AAA or USDA Choice or better) and with high lean yield (i.e. Canada 1 or USDA 1 or 2) are desired while those with minimal marbling (Canada A or USDA select) or that carry excessive finish (Canada YG 3 or USDA YG 4 or 5) are not. Again depending on the packer, premiums can be paid for desired carcasses (such is the case if one markets under a grid or branded beef program) and discounts applied to off-grade carcasses.

A further confounding factor is the requirement to achieve desirable carcass weights. Most packers require carcasses to fall within specified limits, which in turn dictate the live weight of the cattle at slaughter. For example, when selling on the rail, it is not uncommon to see a specified carcass weight range of 700 to 900 pounds. At 59 per cent dressing percentage, this translates to a live weight range at slaughter of 1,185 to 1,525 pounds. Most feedlots today are marketing cattle at the upper end of this range and in some cases well exceeding 1,500 pounds. In terms of carcass grading, this practice has positive and negative attributes. Quality grades (i.e. marbling) are improved with time on feed, however, yield grades suffer as overall carcass fat content increases with increasing weight, particularly during the latter phases of finishing. Another concern is what is happening to feed efficiency as you hold cattle for an extra 30 to 60 days to get that extra 100 to 200 pounds. Cattle that had been converting at 6.5 or seven to one (i.e. pounds feed to pounds of gain) may now be converting at 7.5 to 8.5 to one or greater, a cost which may or may not be offset by the increased value of the weight gain.

If achieving desired carcass grades while maintaining efficient gains seems like a difficult task, then I have been successful in getting my point across. It is indeed a challenge! To understand how they achieve this task, one needs to look at how feedlots use a combination of backgrounding, grass and finishing programs to manipulate frame, muscle and fat development in the cattle they feed. For example, depending on the weight and genetics of the calf at weaning, it could go right onto a finishing program (as in the case of a large-frame calf weighing 600 pounds or more at weaning), be backgrounded over the winter and go into the feedlot as a short yearling (i.e. at a year of age) or in the case of lightweight calves, spend a second summer on grass and go on feed as a long yearling (i.e. 18 months of age or so). These management programs along with appropriate technologies such as implants to enhance growth and ionophores for feed efficiency allow feedlot operators to feed just about any class of cattle to the appropriate weight and carcass grades demanded by the packer. Indeed — no small feat!

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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