Ron Rosmann: I was really happy with this study in the sense that every question we were asking and hoping would be positive turned out positive. CLA content was higher, there were no differences in taste and tenderness, and economic returns were better. Something we still don't know is what's really desirable for human health. Roberto Sonon did most of the work. We both thought, sure we have these ratios, but we don't know what's really desirable as far as the human diet. Is there research out there that tells you what ratios are good, what's enough, what's not enough? We need dietary studies on humans.

We were aware of some other researchers doing work on grass-fed animals--among them Dr. Tilak Dhiman at Utah State University, and I've spoken with Dr. Dhiman. But we couldn't find values at the time to compare with what we were looking for. There's a lot of anecdotal information. And I think what was available from Dr. Dhiman was on butter, eggs and dairy. We didn't find data regarding meat products.

The one thing that was most eye-opening was that nobody had even looked at this part of the equation yet. I couldn't find any references in a literature search about comparing grass fed to corn fed animals for CLA content.

Roberto Sonon: In previous studies, CLA has been shown to be higher in animals on pasture under research conditions, but this had not been tested in a farm-based setting. And now we’ve determined that in a farm setting. We found that pastured animals, even if supplemented with a concentrate to obtain desired meat qualities, obtain higher CLA levels. That is the biggest finding.

Ron Rosmann: We modified a few things in our management based on the results. For instance this spring we took all of our yearling cattle--they'd over wintered in the yard eating roughage with no corn in their diet, they were fed silage, hay and ground oats—in April they all went out to grass and as a supplement we fed them ground oats 7-8 lbs per head per day, from May 1 to end of August. After that we put them in the feedlot, and grained them the last 90-120 days. We put them in the feedlot because we're faced with a marketplace that rewards for Choice 1s and 2s [grade]. But this process does cut the costs down. We haven't changed our marketing. We're still responding to the market demand for grain-fed choice beef, but producing it differently.

But right now for economic reasons we're trying to do everything to not feed corn, because we can sell all the corn to the big three: the organic beef industry, the organic broiler industry and dairy industry. From what I understand, the market for organic corn is about 1/3, 1/3 and 1/3 in those categories, roughly.

We have at times thought about using a "higher CLA content" meat label, but marketing grass-fed beef is still difficult. While we do also produce a fully grass-fed beef, I really don't have any demand for it--it has only been requested by one retail customer. For the rest, it doesn't register as an issue of importance.

Roberto Sonon: That is an interesting thing about this, that the farmer wants to produce leaner and healthier beef but the market calls for these top choice grades, so the farmer is caught in between.

Ron Rosmann: So we didn't market it as grass-fed. But no one complained about the quality, and as far as we know, they couldn’t tell the difference. It’s also exciting to think about other factors we can try such as adding flax to feed. We're going to grow flax next year. It’s been suggested that the flax straw, too, is good for cattle. [Flax is high in omega-3 content.]

Roberto Sonon: Already there are products on the market labeled "high omega-3 content, based on flax in the animal's diet--most notably eggs. In monogastric animals such as chickens, pigs and humans, omega-3 is transferred readily from these diets. But not so much in beef, because of their multiple stomachs. So for example feeding flax to chickens will easily raise level of omega-3 in eggs and chicken meat products. It will be interesting to see the results of feeding flax to cattle.

The project report includes some technical terminology. [For readers who download the full project report, this information may be helpful.] The first example is the data on fatty acids and other values for ribeye steak, adipose tissue and trim. Adipose tissue is taken from the back of an animal, specifically in the underarm area. In layman's terms it is fat, but adipose tissue is not eaten. Trim is material that is generally used in meat products, such as hamburger and other ground meat products. It is fat that is blended with or used with the muscle, while adipose tissue is not.

The second example is the “atherogenic index." The atherogenic index relates to the LDL:HDL ratio. LDL refers to low density lipoprotein, which is known as “bad” cholesterol. HDL, or high density lipoprotein, is known as “good” cholesterol.

We have a formula for calculating the atherogenic index (AI):

AI=

%C12:0 + 4X C14:0 + C16
-------------------
Sum of mono and saturated fatty acids
+ polyunsaturated fatty acids

Where C12 = Lauric acid;
C14 = Myristic acid; and
C16 = Palmitic acid

These fatty acids, C12 through C16, shown in the numerator of the formula, are considered “bad” fatty acids, contributing to LDL. These are the “most atherogenic” fatty acids, resulting in higher cholesterol content in the blood. Therefore, the lower the AI, the healthier the product. As consumers, we want to look at this ratio. The higher the ratio of n-3 (omega-3) to n-6 (omega-6) fatty acids, the healthier the product. In this case, the higher the omega-3 fatty acid content, the greater potential health value of the beef.

In Table 4 and Table 5 of the full report, the ratio value n-3/n-6 is derived from the sum of all the n-3s in the column, over the sum of the n-6s in the column. Note that 80% of the n-3 is derived from C18:3n-3: linolenic acid. While there are other n-3s they are less present or undetectable. So really what we're looking for is product with the highest C18:3n-3 content.

To a layman, based on numbers alone, the "good" and "bad" fatty acids appear similar. For example, conjugated linoleic acid (CLA), which is “good”, is identified as C18:2, while C18:2n-6 is Omega 6, which is “bad.”CLA is made up of isomers of C18:2. CLA is an isomer that has been found to benefit humans.

There is one important point on comparing the presence of omega-3s and omega-6s and CLAs: You will find the omega-3 and omega-6 fatty acids in the feed, which is why we test for them in the feedstuffs. But you won't find CLA content in the feed because CLA is synthesized in the adipose tissue of the animal and in the stomach, so this is why adipose tissue is tested, even if we don’t use it as a food product. It is expressed in the body of the animal and in animal products, such as dairy. If you look again at Table 6, there are five columns of identified CLA isomers. 80% of these isomers are held in c9, t11 [column 2]. The following three columns are also isomers. However, c18:1t11, shown in column 1, is not really a CLA isomer, but it is shown because it is a precursor for synthesis of the isomers, so it is important to know this value.

Another point about CLA is that it is readily expressed in dairy products. The difference is very dramatic, more so than in meat products, as high as five-fold.

Ron Rosmann: If we want to take this research to where it really needs to go—which could take the rest of my life and then some—what we'd want to do is look toward the right mix of quality of forage and the right genetics in cattle to get them to grade choice on grass. They'd have marbling, taste and tenderness. I think it's possible by selecting genetics of cattle that have a deeper body. These are generally the English breeds, black angus and red angus. Though you have to take into consideration that even the genetics of Angus have changed of late--they've been bred for other qualities and to finish on grain. But there are some people working on this. We really don't know effects of pasture quality, either. So it's genetics and pasture managemen--the two big things to look at in the future, these definitely need more research.

Roberto Sonon: Since this work was conducted, I’ve transferred to University of Georgia, where I’m continuing this kind of work. Also, there is a SARE project proposal that I worked on while at Iowa State, prior to transferring to Georgia, that has been funded to do this study in humans-- those human studies Ron was talking about. Stay tuned.

This commentary is based on interviews conducted and edited by Erica Walz, December 2004.

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