Just how much meat are your cattle producing?
By: Bill Halfman, University of Wisconsin Extension Ag Agent and Dan Schaefer, University of Wisconsin Department of Animal Science
During the past few months I have had a number of discussions with folks on dressing percentage of cattle and how come theirs were less than the numbers we typically use or expect to see. Most of these questions were from people who direct market some of their animals and sell on hanging carcass weights. These questions have been asked enough that a review of this topic is likely helpful to others.
Keep in mind that dressing percentage is defined as hot carcass weight divided by live weight times 100. Numbers often used to benchmark dressing percentage for steers are 62 for beef breeds and 59 for Holsteins. There are reports now of commercially raised beef steers achieving a dressing percentage of 65. These numbers correspond to a live weight taken at the packing plant for a yield grade 3 steer carcass that will grade choice, and is finished on a high grain ration, (not more than 20 percent roughage) and the carcass is weighed while still hot, i.e. hot carcass weight. In addition, the animals are clean. To help keep a perspective on dressing percentage, if a steer has a live weight of 1300 pounds, it only takes 13 pounds of non-carcass live weight to reduce dressing percentage by 1 percent.
Let’s consider factors that affect dressing percentage. To organize our thought process, let’s begin with factors that affect the live weight used in the dressing percentage calculation.
Weighing conditions affect the live weight, especially if the live weight is determined at the farm versus at the packing plant after unloading. If the weight is taken at the farm, there will be loss of live weight during its transport to the locker plant. During loading and trucking, the animal defecates and urinates. This is lost live weight. Even a short haul of 5 miles can result in a loss of 3% of live weight. Dressing percentage calculated on the basis of live weight taken at the locker plant will be greater than dressing percentage based on an on-farm live weight.
If the animal has not had access to feed overnight prior to weighing and trucking, then the animal is pre-shrunk before weighing so weight loss due to trucking will be less and gut fill at the locker plant will be less. To boost the dressing percentage of your cattle, withhold feed and water for 24 hours before slaughter. Under most circumstances that occur on the farm and during trucking, live weight loss is due to water loss from the digestive tract and the bladder, and not from carcass weight loss.
The weight of the digestive tract is affected by the forage content of the diet. Cattle finished on a high-grain diet will have a smaller percentage of their live weight present as digestive tract than cattle finished on a high-forage diet. Forage is much bulkier than grain, so the digestive tract must be larger. Research trials conducted in Alberta Canada showed that the amount of gut fill due to roughage percentage in the diet reduced dressing percentage from 2 to 8% compared to a typical low roughage finishing (20 percent roughage or less) rations. Higher percent roughage in the diet led to greater decreases in dressing percent. Cattle finished on a high-grain diet will have a higher dressing percentage than cattle finished on a high-forage or grass-based diet.
Let’s say someone fed a lot of salt to finishing cattle just prior to slaughter to boost their water intake and live weight, what would that do to dressing percentage? What if someone fed a lot of sand in the diet of finishing cattle just prior to slaughter, what would that do to dressing percentage? In both cases, the added weight does not become carcass weight so dressing percentage would be lower.
What if cattle have dirty hides or have horns? What if a finished heifer is pregnant? The manure, horns and fetus don’t become carcass weight, so they result in a lower dressing percentage. It does not take a very big pile of mud and manure to weigh 13 pounds (using our example from earlier) and if it is wet the pile is even smaller.
Now let’s examine factors that affect the carcass weight. The carcass is usually considered to be the weight remaining after removal of blood, hide, tail, head, lower legs, and all visceral organs. Again, what are the weighing conditions of the carcass? It is typical that the carcass weight is obtained immediately after the carcass is washed following evisceration and before it enters the cooler.
If the carcass is allowed to hang in the cooler for 14 days to dry age for improved tenderness, moisture will be lost from the carcass muscle due to evaporation, though a uniform covering of fat will minimize this evaporative loss.
Kidney, pelvic and heart fat (KPH fat) may or may not be included in carcass weight. Some locker plants may include heart, liver and tongue when weighing the carcass. If so, this will increase dressing percentage. The absence of the organs and KPH fat may lower the dressing percentage by 4 to 5 percent.
The degree of body fatness influences dressing percentage. Body fat is deposited within the body cavity, between the muscles, within the muscle or meat – called marbling, – and just beneath the hide. Since much of this body fat stays with the carcass at slaughter, increasing body fat results in higher dressing percentage. Finished Holstein steers have 0.25-0.3 inches of fat cover while beef steers often have 0.4-0.7 inches. This is one reason why beef steers have higher dressing percentage than Holstein steers.
Muscle to bone ratio in the live animal and in the carcass also influences dressing percentage. Heavier muscled cattle have higher dressing percentage. To continue the earlier comparison, Holstein steers have a lower muscle to bone ratio than most beef breed steers. This, too, accounts for a lower dressing percentage in Holstein steers than most beef breed steers. Big-boned beef cattle with below average muscling would also have low dressing percentage.
In contrast, technologies have been developed to increase the proportion of muscle in cattle. These include use of anabolic implants and feed additives called beta-agonists. When these technologies are implemented, dressing percentage will be elevated compared to those cattle that do not receive these technologies. Use of these technologies have led to dressing percentage of 65 in beef steers.
In summary, there are a number of factors that influence dressing percentage, some of them affect live weight and some of them affect carcass weight. The factors that play a big role include gut fill, shrink, cleanliness, fat cover, degree of muscling and finishing ration forage content. It is very likely that if you encounter an animal that is quite different than the expected dressing percentage, there are probably several factors involved.