Philip mentioned another benefit for grass fed beef in the comments of the previous post: CLA, Conjugated Linoleic Acid. He cited the Wikipedia entry:

Antioxidant and anti-cancer properties have been attributed to CLA, and studies on mice and rats show encouraging results in hindering the growth of tumors in mammary, skin, and colon tissues.[13][14][15][16][17][18][19][20][21] [22] [23][24][25][26][27] It has been reported that CLA can up-regulate the tumor suppressor gene PTPRG, and may have anti-cancer properties.[28][14]

A European team led by the Swiss scientist Lukas Rist has found that mothers consuming mostly organic milk and meat products have about 50 percent higher levels of rumenic acid in their breast milk.[29]

Some studies of CLA in human diets show that it may reduce body fat,[30] especially abdominal fat. A maximum reduction in body fat was achieved with a daily dose of 3.4g.[31] However, some experts do not recommend taking CLA supplements. CLA supplements contain high levels of the t10,c12 CLA isomer, which has been linked to multiple side effects.[32] Supplementation with this form of CLA has been shown to increase C-reactive protein levels, possibly to induce oxidative stress,[33] to reduce insulin sensitivity, and to increase lipid peroxidation.[34] In contrast, the cis-9, trans-11 CLA isomer, the primary form of CLA found naturally in beef and dairy products, has been shown to protect cells from oxidative damage by increasing glutathione levels without inducing lipid peroxidation.[35] It is possible, however, that the observation of markers of increased lipid oxidation may indicate potentially desirable lipolytic effects. Further studies are necessary to establish the clinical significance of such observations.

Possible adverse effects of CLA in humans

There are concerns that the use of CLA supplements by overweight people may tend to cause or to aggravate insulin resistance, which may increase their risk of developing diabetes.[8] Most supplements contain mixtures of two CLA isomers: the cis-9, trans-11 isomer (the predominant CLA isomer in milk and beef) as well as the trans-10, cis-12 (t10c12) isomer. It is the trans-10, cis-12 isomer that is linked to many adverse side effects. Research indicates that supplementation with t10c12 CLA dramatically increases rates of oxidative stress, to levels considerably higher than that observed in heavy smokers.[8] However, the evidence is controversial, and some studies using a mixture of c9t11 and t10c12 CLA showed no changes in insulin sensitivity.[36][37] Although researchers are still not sure of the long term health effects of consuming CLA from supplements, foods naturally enriched in CLA, such as beef and dairy, are a safe alternative.

I find it odd that getting the safe version of CLA (the cis-9, trans-11 isomer) from beef and dairy is called an "alternative". How did our dietary habits get so twisted that a natural food is considered to be an alternative to the pills, powders and supplements that supposedly health conscious people gobble with abandon?

The CSU Chico study referenced in earlier posts says much the same as the Wikipedia entry but is perhaps a bit clearer.

CLA is found naturally in a variety of ruminant meats (French, et al, 2000) and dairy products (Dhiman, et al, 1999), due to the anaerobic activity of the rumen bacterium Butyrivibrio fibrisolvens. This rumen organism is responsible for the biohydrogenation of linoleic and linolenic acids into the conjugated isomers referred to as CLA. Because linoleic and linolenic acid is a precursor, diets rich in these compounds increase the concentration of the CLA within the fat depot of the animal. Lush green forages are high in this precursor, therefore, grass-fed ruminant species have been shown to produce 2 to 3 times more CLA than ruminants fed in confinement on concentrate-only diets (French, et al, 2000; Duckett, et al, 1993; Rule, et al, 2002; Mandell et al, 1998). . .

To achieve biological effects, the average human would need to consume approximately 5 grams CLA/day. On average, a single 3.5 oz. serving of grass-fed beef provides 1.23 grams of CLA, 25% of the daily requirement for a biological effect. Conversely, conventional beef provides 0.48 grams in a 3.5 oz. serving, providing 9.6% of the CLA needed for positive physiological effects.

Grass-fed beef, coupled with the consumption of grass-fed dairy products could provide higher daily doses of CLA from dietary sources, providing the concentration of CLA needed for a positive healthful effect. . .

There is a rising interest in consuming health promoting foods. A scientific basis on which those decisions can be made, provide for sound marketing and purchasing of foods. Beef in general supports considerable healthful compounds, including a high proportion of monosaturated fatty acids, a number of vitamins, minerals and all the essential amino acids. However, the effect of diet, such as forage or grass only diets can enhance the proportion of CLA, omega-3 fatty acids and improve the concentration of Vitamins A and E. The scientific literature supports the hypothesis that grassfed beef contains a higher proportion of healthful lipids and antioxidants important to human health as compared to conventional beef.

IMV the serving size is too small. 3.5 oz.? Whatever. Perhaps it is that those of us who do physical labor tuck away larger quantities of food and still stay lean because we just burn it up working. Food really matters to me. If I don't reload regularly then I power down. Still, it seems to me that it would be better to up the serving size of beef and skip some carbs if you are worried about weight gain. I'll take the healthful vitamins, minerals, protein and fats rather than the sweets of carbs, though I do enjoy dosing with complex carbs such as whole wheat and brown rice, stuff that burns more slowly for extended power, and that seems to provide a nice digestive balance.

Perhaps not surprisingly, I think of my own ration in ways similar to that of my livestock. They need a balanced ration that includes energy foods in order to get the most benefit from their proteins and fats. I even consider the time of day when moving them to fresh forage since the energy value of the forage varies: it's sweeter in the late afternoon and early evening due to having spent the sunny day photosynthesizing sugars. They will graze a fresh, lush paddock at that time of day with gusto, and then have the cooler night time for digestion, which makes a lot of heat and can stress them in the heat of the day. That's also when the forage has the most nutrients that are converted in the rumen to healthful compounds such as CLA.

I suppose that this sort of mindful attitude is a consequence of raising your own food. I'm not just making a living, I'm feeding myself. I'm not suggesting that you too should raise your own beefs. I'm pretty good at this and almost certainly will do it better as well as more cheaply than you can do it yourself. I'm just saying that self-interest provides an extra motivation for me to do good work, and that may be a factor that has some generality that you can take into consideration when deciding which products to acquire for yourself.