Meat scientists work to enhance marbling in beef cattle
Several university researchers are collaborating to find ways to increase marbling in beef cattle without adding extra days on high-concentrate diets.
"With high feed costs and the high cost of gain for cattle feeders, what if we could achieve the same degree of marbling with less days on feed?" said Texas Tech meat scientist, Brad Johnson. "We feel that that's where the economic advantage is."
Johnson has been working on a five-year study, along with Ki Yong Chung, also of Texas Tech, Stephen Smith and Seong Ho Choi of Texas A&M University and Matthew Doumit of the University of Idaho to better understand regulation of marbling development by fatty acids in beef cattle.
The study was funded by the Kansas Beef Council through Beef Checkoff funds.
Johnson began work on the project while at Kansas State University. He joined the Texas Tech faculty three years ago as the Gordon W. Davis Regent's Chair in Meat and Muscle Biology. The findings of the team's research to date were presented at the American Meat Science Association's Reciprocal Meat Conference held in Manhattan earlier this year.
"We know marbling increases the palatability of beef, the juiciness and indirectly increases tenderness," Johnson said. "Cattle on grass tend to have lower marbling scores than corn-fed cattle. Grass is very high in a particular fatty acid--alpha Lenolenic acid, and we feel that a little of that moves through the rumen and could actually repress marbling development in beef cattle."
On the other hand, in feedlot cattle, starch from corn and grain sorghum in the diet elevates levels of oleic acid, which is a monounsaturated fatty acid. The research team believes that fatty acid is important in stimulating marbling development in cattle, he said.
While there's not always a big difference in the price spread between choice and select--two beef grades that indicate the amount of marbling (fat within the muscle)--over time there's enough of a price difference to show that the amount of marbling does matter, he said.
"We've been able to take these cells out of tissue and grow them in a culture system and add specific fatty acids to see how that impacts differentiation of cells into marbling," Johnson said. "We've also looked at potential receptors that are imbedded in the cell's surface, and have found that marbling at different sites--the cells that make up marbling--have a different profile of receptors than say, backfat at different sites. We felt that we can manipulate that difference to enhance marbling without making the cattle fatter."
He cited work by Smith at Texas A&M, that's shown that the older the animal, the less some of the receptors are available in backfat, which would imply that marbling should come a little easier with age.
"With the cost of gain the way it is, feed efficiency is so critical to feedlot operators. We feel that if we can enhance marbling with fewer days on feed or less expensive feed ingredients, that would be a win-win situation," the researcher said.
"The bottom line is that triggering these cells probably at a very early age to become marbling at different sites, and let them lay idle for awhile, once we bring them into the feedlot, they should really enhance marbling," Johnson said. "That's the ultimate goal that we're trying to achieve."
Johnson said the breed of cattle makes a difference.
"Some breeds typically found in the U.S. system have a higher propensity to marble," he said. "But the ultimate gold standard is to look at the Asian breeds, such as the Japanese Black, a Waygu breed in Japan, Chinese Yellowtail and the Korean Hanwoo cattle, those cattle have a high ability to deposit marble. Interestingly, they tend to be lighter muscled, and if you look at our U.S. production system, we tend to select a little more balance for muscle and marbling. Also, from a management standpoint, about everything we do in the feedlot to enhance growth, like steroidal implants, we enhance muscle but we have the opposite effect on marbling."
Marbling scores are independent of market weight, the scientist said.
"With typical breeds in the U.S., we tend as cattle feeders, to talk about another two to three weeks on a pen of cattle. Generally what will happen is we will allow some of those greener cattle to catch up and maybe express their genetic potential to marble. Those cattle that were already an average choice or low choice three weeks prior, they don't necessarily go up (in marbling score) anymore," he said. "So we allow these other cattle to catch up in a pen. But it's well established that more days on feed is not going to change the individual animal's marbling score dramatically, even as we increase the weight of those animals."
The opposite is true with Asian-type cattle. They tend to grow at a slower rate of gain for long periods of time, Johnson said. They tend to increase marbling as the number of days on feed are increased, so there's a genetic difference in those cattle.
"My long-term goal is to come up with some sort of intervention strategy--a feed additive or implant similar to what we administer to cattle for growth enhancement -- where timing may be critical with the ultimate goal to turn on marbling, but not make the cattle fatter," he said. "As we increase overall fatness in cattle, feed efficiency worsens. Obviously in today's paradigm, we can't have that with the way feed costs are."
Johnson also cited work by Texas A&M's Smith on oleic acid in marbling: "Generally, as we increase marbling, we increase oleic acid concentration and Dr. Smith has done a lot of work showing the human health benefits of increased oleic acid. The goal, from a beef demand standpoint, is to show that increased oleic acid is heart-healthy and positive for human health. If it's positively correlated to more marbling, that's a win-win situation for the beef cattle industry."