I was responding to an email from someone who grazes hogs in a oak forest. They wondered about the effect this would have on the linoleic acid content of their pork. As I was responding, I thought that this was an email a lot of people might like to read, so I am posting a copy of my response below.
My response is off the cuff and by the time I’m posting this 10 minutes later I’ve already had several more thoughts.
I mention D6D in the email. Read more about it here.
California Native Americans only removed the oil from oilier species of acorns.
Overall, I guess my answer is, “It depends on the specific linoleic acid content of the acorns (which is currently unknown), the acorn content of the diet and the breed of pig”.
I half-teasingly suggested a GoFundMe project to send different species of American acorns in for linoleic acid testing to have somee kind of publicly available data. If there was interest in this I’d consider sponsoring it. Testing total fat content of an acorn sample is cheap: 20 bucks. Testing linoleic acid content is 200 bucks per sample plus postage/etc. And it takes real time to collect, clean and dry acorns. But still, if we collected 2500 bucks (or whatever), we could collect a lot of data. I’m just thinking out loud, but if anyone wanted to help administer a project like that I’d be all ears.
There are a lot of variables in play here! First, as you know, there are a lot of different types of acorns. This study shows the wide variations in oil content of American oaks, with Red Oaks generally higher in oil (ether extract) than white oaks. https://sci-hub.wf/10.1111/j.1365-2621.1971.tb15133.x# Furthermore, this Turkish study showed that red oak (Quercus rubra) only has a linoleic acid content of ~35%, which is very HIGH for an acorn, which are more typically in the 15-25% range. https://www.researchgate.net/publication/303924535_Fatty_Acid_Composition_in_the_Acorn_Oil_of_Quercus_rubra_L_Cultivated_in_NW_Turkey But then for some reason, all acorns in Turkey seem to have high linoleic acid contents for reasons that are probably unknown: https://www.hindawi.com/journals/jfq/2020/8898370/tab1/ I've never found linoleic acid content of American acorns, although this would be a fun project to send in acorns from around the country. GoFundMe acorn study?! Anyway, to calculate final linoleic acid content, you have to multiple the percent of total fat (ether extract) of the dry weight (after you've dehydrated it) by the linoleic acid content of that fat as a decimal. 35% = 0.35. 17.5% = 0.175. Then multiply your answer by 100 to get back to percentages. A white oak acorn at 10% fat and 15% linoleic acid has (0.10 x 0.15 X 100) 1.5% linoleic acid by weight, not much higher than barley. A red oak acorn at 31% fat at 35% linoleic acid would be way up at (0.31 x 0.35 x 100) 11% linoleic, which is A LOT! By comparison, very roughly: Barley: 1.3% Corn: 2.5% It might be worth collecting a bunch of acorns, separating out the nutmeat, putting them in a dehydrator for a couple days and bringing them to your local testing lab to get a cheap test of water/carbohydrate/fat content. That won't tell you linoleic acid content, but it'll tell you total fat. If you can test by individual species and identify the species, this would be very helpful! On my farm, I can test Northern Red Oak. It's also worth pointing out that acorns are only available for a few weeks of the season and even then, they're probably a relatively small part of the diet, depending on your stocking rates and supplemental feeding practices. As to soybean meal. With a barley based diet and a bit of supplemental lysine - 8 lbs per ton, it costs about a dollar/lb - you can eliminate the soybean meal altogether for pigs on pasture. This will save you money. This is extensively reviewed in the literature, but my study is here:Final report for FNE18-891Additionally, the breed of pig makes a huge difference as to what they'll accumulate. An old-fashioned, fattier breed such as mulefoot or old-fashioned berkshire will accumulate much less LA than will a modern white breed or crosses thereof. My untested theory is that the difference between modern lean breeds and old-fashioned breeds is that the lean breeds have a low activity of an enzyme called D6D - this enzyme converts linoleic acid to arachidonic acid and the downstream oxidized linoleic acid products such as 12-HETE. 12-HETE activates the AhR and causes NAD+ deficiency and therefore fat accumulation. Pigs which have low D6D activity accumulate linoleic acid and remain lean! That's a bit counterintuitive, but there it is. Brad
I sell low-PUFA pork over at Firebrand Meats. I use old-fashioned berkshire hogs and a diet based on low-PUFA, high starch waste products leftover from making products for human consumption such as pea protein isolate. It is a sustainable way to make healthy pork. Recent testing showed it has only 6%linoleic acid! This compares to 16% in Smithfield bacon.
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