Cattle at experimental feedlot facility. "We consume all of the grease that's produced in San Diego and L.A. right down here in this feedlot."
  • Cattle at experimental feedlot facility. "We consume all of the grease that's produced in San Diego and L.A. right down here in this feedlot."
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Fat is plentiful. Fat is cheap. What's more, it's "energy dense," according to Dr. Richard Zinn, a professor of animal science at the 280-acre University of California at Davis Desert Research and Extension Center just outside the wasteland-defying patches of green that surround El Centro. This combination makes fat an attractive food supply to feedlot operators, who want to "maintain an acceptable rate of production and also, produce a carcass that has characteristics a consumer wants," while spending as little as possible. Thanks in part to the center's work in researching the effects of supplemental fat on feedlot cattle, "probably 80 percent of the cattle on feed are receiving fat" as part of their diet.

Dr. Richard Zinn (left) and Ernie Fusi, senior animal care technician. "In order for marbling to occur, "the animal has to achieve chemical maturity -- intramuscular fat deposition is one of the latter stages of fat deposition in the animal."

Dr. Richard Zinn (left) and Ernie Fusi, senior animal care technician. "In order for marbling to occur, "the animal has to achieve chemical maturity -- intramuscular fat deposition is one of the latter stages of fat deposition in the animal."

"The fat that we're talking about, mostly, it's made up of restaurant grease," explains Zinn, a square-jawed, self-contained man with rimless glasses and close-cropped hair. "It's what McDonald's and Burger King and all those other restaurants use. They cook a few french fries for a while, then that fat that's left over, you can't dump that down the drain. So, they'll put it in barrels, and then those barrels are collected by a company that will recycle the fat, filter it and centrifuge it. Then what we call the yellow grease will be sent back out to the feed lots as a feed ingredient."

The fat arrives in liquid form by train car or truck, 50,000 pounds per load. That's enough to keep the fat level in the feed for the center's 20,000 head of cattle at roughly 4 percent for three or four days. In all, Zinn estimates that 40,000 tons of fat (at $300 a ton) are delivered to the center each year, with each head of cattle munching about 140 pounds of the stuff before its journey to the slaughterhouse. "We consume all of the grease that's produced in San Diego and L.A. right down here in this feedlot," he says, noting that some of it does go to poultry.

The trucks pump their yellowish cargo into the center's four fat tanks, tanks which, thanks to the insulation that has been applied to their exteriors, have an appropriate pasty-white, lumpy cellulite look. Another tank holds molasses. The tanks stand outside a small barn; inside is a maze of pipes, pumps, and containers. Come mixing time, a person standing at the control box pushes a button and pumps the warm fat into a weigh hopper, then into a perforated bar, which sprays it down onto the feed.

Because it's energy dense, "fat happens to be one of the most important by-products that are fed back." Others include "Wonder bread and all the stale bread from the stores, chocolate chips that are turning white, and chewing gum that's gotten hard," along with more expected leftovers, such as rice straw. Zinn anticipates the consumer's hesitancy to imagine such a diet producing "carcass characteristics a consumer wants," such as lean meat, and is quick to reassure. "We go over to the packing plant and follow the cattle through the slaughter and evaluate the carcass. We look at fat distribution, take samples and measure composition of fat. There was a little bit of an increase in kidney, pelvic, and heart fat, which is what you'd expect, but it's small. It had very little effect on carcass composition."

Carcass composition is what brought me here: is science working to build the consumer a better steak? Zinn says yes, telling tales of experiments being done at Oklahoma State wherein cattle are fed "very high levels of vitamin D during the late finishing phase. It increases the absorption of calcium into the meat, and that calcium helps stabilize some of the enzymes that begin to break down the protein and make the meat more tender. They can increase the tenderness maybe 15, 20 percent by that practice." The practice is still experimental because the vitamin D may have a negative effect on "feed efficiency -- average daily weight gain." Also experimental is injecting the carcass with calcium after slaughter.

The use of enzymes to tenderize meat is not a new idea; what's new is the timing. "Those meat tenderizers you sometimes see people put on their steak are protolytic enzymes that begin to break down the tissues. Aging will do the same thing, but we don't age meat too much anymore. There's still some of that going on in fancy restaurants, but...the taste of aged meat is sometimes a little bit unacceptable, because it has that riper, fruitier flavor. Feeding high levels of vitamin D is kind of like enhanced aging without the side effects of microbial growth and the flavors that it produces -- oxidized fats and that type of thing." While your steak is still walking around, it's gearing up to decompose.

Why the emphasis on tenderness, as opposed to flavor? In his Ethics, Aristotle claims that most people, or at least the intemperate, derive enjoyment not from flavor, but from touch, "and it is in view of this that a certain gourmand prayed that his throat grow longer than that of a crane, thinking that by extended contact he would be pleased."

Zinn supports Aristotle's claim. "When you evaluate meat, you evaluate it on four criteria: tenderness, juiciness, flavor, and overall acceptability. Tenderness accounts for about 90 percent of the overall acceptability of the cut. It could have no flavor, but if it was tender, people are going to rank it real high. You want a piece of meat that's tender and juicy and flavorful, but when it gets right down to it, the average consumer, the above-average consumer, wants tender meat." He cites the results of tastings done by trained taste panels, a group of feedlot operators, and his own tongue as evidence.

This accounts for science's recent efforts to come up with a system for predicting the tenderness of meat. Right now, part of meat grading is based on marbling, the amount of intramuscular fat in the carcass. Prime, "the top one or two percentile in degree of marbling," tops the list, followed by choice, "anything between a small amount and an abundant amount," and select, "between trace amounts and slight." Zinn laments this system, saying that "marbling is not a good predictor -- it's not correlated with tenderness. Marbling enhances the juiciness of meat, [and] those fats carry the seasoning throughout the meat," which improves flavor. But when it comes to tenderness, marbling won't help.

What helps is days on feed, as opposed to days on grass or some other stocker. When grading standards were created in the early 1900s, the predominant breeds of cattle in America were English -- Angus, Hereford, and Shorthorn. "In order for marbling to occur," says Zinn, "the animal has to achieve chemical maturity -- intramuscular fat deposition is one of the latter stages of fat deposition in the animal." Since these breeds tended to mature early, they marbled by the time they reached market weight and age, about 1250 pounds and two years -- if they were on feed long enough.

"The degree of marbling was a reflection of the days the animal was on feed. The more marbling within a certain window of age, the longer the animal was on feed during that certain window of age. If you take an animal that was fed on grass, and if that animal doesn't have any marbling by the time it's two years old, then it can't be graded, because it's too mature. We know that the meat's going to be a little bit tougher."

It wasn't only the marbling graders were after, though that was part of it, since more people liked to eat fat back then. It was the guarantee that the cattle had spent enough time on feed to make them tender. But after a while, the sign got equated with what it signified. People thought marbling meant good eating, and these days, there's no necessary connection between the two.

For one thing, Angus, Hereford, and Shorthorn aren't the only breeds around anymore, and other breeds might reach market weight without marbling as much, since they mature more slowly. For another, here in the Southwest, calves are often put on feed as soon as they are weaned, with no time spent on grass or stockers. They spend the same amount of time on feed as grass-fed cattle but reach market weight sooner, meaning less time for fat deposition.

"If you just knew where the meat was grown, if you knew that it had some days [on feed]," wishes Zinn. "All the meat that's produced here in the valley is going to have been on feed almost 240 days, and Holsteins for 280 days. That makes the meat very tender, but with no marbling." Like mountain-designated water, like vineyard-designated wine, region can influence your beef.

Marbling isn't bad. Sometimes, meat retailers who advertise lean meat stop paying so much attention to days on feed, and marbling does protect you against underfed beef. But marbling isn't especially good either, at least not for predicting the degree of pleasure your steak will bring you. Which is what Zinn is after, despite what you may think of Bessie chewing a cud of Wonder bread, ancient Wrigley's Spearmint, and fry grease.

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