If you have been a regular reader of this column, you will know that I often write about the design of backgrounding and finishing programs. In these columns, I focus on formulating diets to specific energy and protein levels that target desired rates of gain for different classes of cattle. In the case of finishing programs, the focus is not just on performance but also on achieving desired carcass weight and grade specifications. In the case of backgrounding programs, the goal is to grow weaned calves to appropriate weights so that they can go to grass or move onto finishing diets without the fear of them finishing at too light a weight. With this and my next column, I would like to look at how the nutrition program influences the market quality of various classes of cattle.
First let’s look at what today’s market defines as “quality.” Yearling cattle typically enter a feedlot at approximately 12 or 18 months of age. In the latter case, they are typically grown out over the winter and marketed to feedlots in the late winter/early spring as “short yearlings.” In the former case, they are marketed off grass as “long yearlings.” Depending on the program, these cattle can weigh anywhere from 850 to 1,100 lbs. The critical quality characteristic is that the cattle coming off these programs carry minimal fat, i.e. they are not over-conditioned! The goal is to develop frame and muscle but minimize fat deposition.
With finishing cattle, the definition of quality is more complicated. In Canada, carcasses from youthful steers and heifers (i.e. less than approximately 30 months of age) are graded for quality and yield by Canadian Beef Grading Agency graders. Quality grades refer to the amount of marbling or fat within the exposed ribeye muscle. Carcasses with trace marbling are graded Canada A while those with slight marbling are graded Canada AA. The two highest-quality grades are Canada AAA and Prime, with small and slightly abundant marbling, respectively.
Yield grades, in contrast, are designed to predict the proportion of the carcass that is saleable at the retail level. While there are several factors affecting retail yield, the most important is the amount of fat on the outside of the carcass (i.e. subcutaneous fat). There is an inverse relationship between the amount of subcutaneous fat and retail yield. The more subcutaneous fat, the lower the retail yield. Canadian yield grades range from 1 to 5, with Canada 1 having the highest retail yield (52.2 per cent or greater), while Canada 5 has the lowest (45 per cent or less).
In today’s commercial market, carcasses with quality grades of Canada Prime and, to a lesser extent, AAA are the most desired, particularly when combined with Canada 1 or 2 yield grades. Although there are some exceptions with cattle of specific genotypes, it is a difficult task to achieve a high marbling grade (i.e. Canada Prime) and a high retail yield (i.e. Canada 1 or 2) in the same carcass. This difficulty arises from the fact that cattle do not lay down marbling fat independently of other fat deposits. Cattle that deposit a significant amount of fat in the muscle tend to lay down fat in other locations such as under the hide (i.e. subcutaneous fat), thus reducing retail yield. There are exceptions to this rule, however, in most cases it holds, particularly if cattle are fed to heavier weights to achieve a higher-quality grade.
Getting back to my original question — how does the design of the nutrition program affect the quality of cattle coming out of backgrounding and finishing programs? Let’s start with designing rations for backgrounding cattle. Remember the goal is to grow cattle in these programs, not finish them. Backgrounding diets should be formulated to achieve specific rates of gain that in turn are based on your anticipated marketing date and target weight. For example, if you are growing 500-pound steer calves to 850 pounds over six months, your program needs to target two pounds per day or slightly less to achieve your target weight. If these calves were destined for grass in the spring, your target weight would likely be less (i.e. 700 to 750 pounds) and target gains of 1.2 to 1.5 pounds would be more appropriate.
Assuming all other nutrient-related factors being optimal (i.e. protein, mineral, vitamins), the two keys to achieving a targeted gain in a backgrounding program are to ensure cattle are consuming at expected levels and that the diet is formulated to the correct energy density (i.e. net energy gain value). Concerning intake, cattle on backgrounding diets typically consume 2.5 per cent of their body weight on a dry matter (DM) basis. This means a 650-pound steer should be consuming around 16 pounds of DM. Choosing the right ration energy density using nutrient tables, “COWBYTES” or the services of a nutritionist is critical, as too high an energy density can cause one to overshoot their target gains while too low an energy density can have the opposite effect.
Next month, we will continue this discussion focusing on the impact of the nutrition program on carcass quality and retail yield grades.