There’s no question that feed can be used to manipulate carcass composition and quality. The ultimate question is what market you want to target.
“The definition of quality can change dramatically depending on the buyer,” says Dr. Heather Bruce, associate professor, carcass meat science, University of Alberta. There are buyers in the market for all types of beef carcasses, from the leanest and largest to a highly marbled product. Knowing your market will help increase your return on investment by minimizing inputs to match the required output.
“Canada’s beef grades for quality and yield are how we define and communicate quality to buyers at home and especially to our export partners. Grading gives us a classification system and many buyers have given values to each classification,” she says.
To qualify to be graded in Canada, a carcass must be from a youthful animal and have at least two millimetres of back fat (subcutaneous fat) and the fat must be firm and white or amber in colour. Only the carcasses with sufficient marbling (intramuscular fat) to make the quality grades of Canada prime, AAA, AA, or A are graded for yield.
Marbling is a historical measurement in Canada’s grading system because tenderness tends to increase as the amount of fat within the muscle increases.
Yield grade is a prediction of the percentage of the carcass that is lean or red meat. It’s based on an equation that uses actual measurements of rib-eye length and width to score the muscle as well as grade fat thickness at a certain point on the outer edge of the rib-eye.
Some buyers may simply judge carcass quality on salable yield or dressing percentage. It’s the hot carcass weight divided by the live weight multiplied by 100.
Stability is an important quality factor that nobody pays for, yet everyone expects, she says. Shelf life is limited by discolouration and the loss of true beef flavour and is influenced a great deal by a tiny portion of muscle tissue called phospholipids.
“Phospholipids make up the muscle cell membranes, so are only about 1.5 to 2.0 per cent of the muscle, but they have a dramatic effect on quality and flavour,” Bruce explains. “Any taste that comes through from feed can be found in the fat of the animal, but any routine changes in flavour will be found in the unsaturated fat of the phospholipids.”
Bruce refers to a 1985 Trenkle study that laid the groundwork showing the effect of ration type on body composition. Four diets were tested: low energy/low protein, low energy/high protein, high energy/low protein, and high energy/high protein. The low-energy diets provided 2.2 Mcal per kilogram of feed and the high-energy diets provided 2.8 Mcal/kg. Metabolizable protein was 5.0 per cent in the low-protein diets and 6.3 per cent in the high-protein diets.
The low-energy/low-protein ration resulted in nearly equal percentages of body fat and body lean.
The low-energy/high-protein ration produced a slight increase in lean with a notable decline in fat.
When the energy level was increased at the low-protein level, lean declined slightly relative to a notable increase in fat.
The high-energy/high-protein diet didn’t equalize body fat and lean as was the case with the low-energy/low-protein diet. Instead, body lean and fat were very similar to the results from the high-energy/low-protein ration.
“What the study doesn’t show is growth,” Bruce adds. “We would expect average daily gain to be very different with the low-energy/low-protein animals gaining much less than the high-energy/high-protein diet.”
Timing the balance of protein and energy can sway carcass quality toward your target.
She suggests feeding low-protein/high-fat (energy) feeds, such as dried distillers grains with solubles (DDGS), early in the growing phase (140 to 250 days of age) because research shows that the increase in fat deposition will persist, especially with marbling score and quality grade, which are so important for increasing value.
“Another practice that’s underutilized is the advantage compensatory growth gives to increasing carcass fatness with less feed,” Bruce says.
“When feed energy is restricted for a short time, for example by putting animals on pasture, and then they go onto a grain-based diet, you can get incredible increase in the amount of subcutaneous fat and marbling because the muscle itself has become so efficient. It hasn’t had a lot of energy and has adapted to a low-energy supply, so once the animal is on a high-energy diet, the body stores extra energy as fat. This way you can take advantage of the increased efficiency of the animal in terms of depositing fat.”
Keeping animals longer is another way to increase marbling and subcutaneous fat, although there is a point, usually noticeable after 18 months of age, when the longer you keep them the tougher they get. A cost-effective way of putting this tip into practice would be to maintain calves on a low-energy/low-protein diet early on and then finish them on a high-energy ration, factoring in transition diets so that the animals don’t become ill from a sudden change in diet type.
Ultrasound is a well-established method of measuring fat cover and rib-eye area in live animals that can be used to sort animals into specific groups on arrival at a feedlot. Animals that have plenty of fat cover could be segregated into a program with lower energy in the diet to still get growth but save on feed costs. The ideal scenario would be to follow up with ultrasound to find out whether the program is working.
Bruce believes sorting and feeding according to weight or average daily gain is theoretically possible in the beef industry if producers know the breed type and the breed’s growth curve. This is something the chicken and pig industries have done so well because the genetics within each of those industries are so homogenous. When animals come off the high-growth phase is when they will start to put on fat, so that’s when energy in the diet can be reduced.
“Beef isn’t to this point yet because of the diversity in genetics, which is a good thing, but a breed association might find a marketing advantage if it wanted to move in that direction,” she adds.
Feeding grain improves quality grade, increases hot carcass weight, and increases dressing percentage by reducing internal organ proportions relative to cattle on high-fibre rations.
Grain finishing also has a positive effect on stabilizing the product to improve shelf life by reducing polyunsaturated fats that contribute to oxidization (going rancid) while maintaining or increasing monounsaturated fatty acid levels.
Much of the new research on feed grains has been on DDGS as this co-product of ethanol production became more widely available with expansion of the ethanol industry. The starch is removed by the fermentation process, leaving a high-protein product that is also high in fibre and fats if the fats haven’t been removed at the plant for other markets.
Inclusion of wheat DDGS doesn’t affect carcass traits. The caution from research is that liver abscess scores tend to increase as the barley-silage portion of the ration is reduced.
Triticale DDGS tend to increase back fat thickness, decrease dressing percentage, and decrease rib-eye area and yield.
Corn wet distillers grain with solubles have no effect on carcass weight, dressing percentage, subcutaneous fat thickness, or yield grade, but do increase marbling and total fat content. Trained taste-test panels have detected an increase in sweetness and “liver taste” of the beef.
One concern with high protein levels is that energy for growth might be diverted to excreting excess protein, thereby reducing dressing percentage. A recent study showed that this was true for DDGS at the very high inclusion rate of 60 per cent of the ration, providing 22 per cent protein during the growing stage. However, the lower rate of 30 per cent (16 per cent protein) didn’t affect final dressing percentage. This study involved early-weaned (134 days) calves fed a ration of corn grain, corn silage with DDGS at the differing inclusion rates for 99 days and then switched to a corn grain-corn silage ration.
Studies have shown that cattle on pasture or forage-based rations have higher concentrations of conjugated linoleic acid (CLA) as total fatty acids, although total fat is less than that of cattle on grain-based diets. CLA is a natural trans fat in beef that is thought to have anti-diabetic, anti-carcinogenic and anti-obesity factors.
“Essentially what happens is that there is so much precursor to the CLA family that the rumen is overwhelmed and the CLA is directly absorbed and deposited into the phospholipids of the muscle,” Bruce explains. “Grains tend to dilute the advantage and with time on feed we see the polyunsaturates and CLA start to decline. That said, if timed right and you test grains to figure out how much could be fed, you could reap the benefit of the grains and also of the previous pasture feeding. There has been very little research on trying to find the balance because of extremes one way or the other.”
In summary, know your market, know the protein and energy levels of your feeds, feed diets with higher energy to increase back fat and marbling, and consider compensatory growth to increase feed efficiency, marbling and back fat at finish.
For more information, visit feedcoalition.com, or Bruce can be reached at 780-492-9871.