Making Fermented Feed for Pigs (recipies and ratios)

We feed a lot of fermented grains to our pigs because it helps them better digest their feed.

To ferment pig feed, soak feed in water for 2-7 days in a covered barrel or bucket. First, the feed soaks up water, then natural yeast forms, making it smell slightly sweet, like bread dough. Next, the feed will take on a slightly sour smell. Use it up at this stage, before it goes bad.

Fill buckets or bins 2/3 with feed (pellets or grains) then add water almost to the top. A bit of sourdough culture or active yeast solution will give it a big jumpstart. In cool weather, using warm water will help it get going. Fermentation rarely happens much below 60 degrees Fahrenheit.

At 40 degrees, the cultured bacteria and yeast may start to die off. If it’s getting colder than 60 during the day, or freezing at night, move the process to a warmer location.

Fermenting feed unlocks additional nutrients for the animals, and it increased the protein while decreasing the carbohydrates in the feed. In essence, it can convert starch to protein.

The yeast and bacteria cultured during fermentation are able to break down complex, long-chain molecules that form undigestible fibers and proteins, like the hard outer shell of grains, corn and pea husks, and hay. Fermenting also adds natural vitamins but can reduce synthetic vitamins in a feed.

Fermented feed can be categorized into two main practices. One is fermenting pelleted feeds. The other is fermenting grains and grain products. When fermenting pelleted feed, you can easily overdo it. They ferment quite fast, and any added synthetic vitamins or proteins can be broken down.

To ferment pelleted feeds, I would highly recommend fermenting for 1-2 days tops. Just enough to notice the sweet smell coming from it, which is about 24 hours at room temperature. That’s enough to add valuable probiotics to the feed and to break down some of the non-detergent fibers in the feed.

One thing you need for pigs, no matter your raising system, is a parasitic worm treatment. The best swine dewormer is Fenbendazole. It’s known by the brand name Safeguard. Safeguard is available as a medicated corn/alfalfa pellet. It’s the only way I can worm my pigs since they won’t stand still for an injection of Ivermectin. It’s easy and cheap.

I use the multi-species version because it’s what’s available in my local store and I can use it for my chickens too. It’s the most effective swine wormer and the easiest to administer. I use it on all weaned piglets and adults twice a year. Don’t go without it.

Roasted grain and soybean should only be fermented very lightly if at all. The roasting process has already broken down the feed and fermenting it can break it down too far, losing valuable nutrients. Unroasted soybean can be fermented with good results.

Feed Value Difference in Fermented Feeds

Fermenting grains can increase the protein by 20-45 percent, depending on how well the fermentation culture colonizes. More importantly, it adds a substantial amount of Lysine to the feed. Basically, the bacteria from the culture are high in protein, including lysine. It also reduces carbs in feed a bit.

I’m going to link to some scientific studies at the bottom of the page should you want to read more in-depth information. It’s important to realize that it can be hard to know exactly how much change will take place by fermenting feed. But we know that it’s almost always a significant improvement.

One very important part of the fermenting process is that is almost totally rids feed of tannic acid. Tannic acid is in most unprocessed plant matter and reduces the digestibility of feedstuffs. Oats and beans are fairly high in tannic acid.

Properly fermenting raw soybean, pea, or oats will improve their digestibility by 10 percent or more in pigs. That helps settle their gut, avoids gastrointestinal issues, and improves fecal formation. Yeah, that’s a thing. Fermenting feed helps pigs’ systems work more smoothly.

How Long to Ferment Pig Feed

Grains can and often should be fermented up to the point that they go from a sweetish to a sour smell. If you keep going, it can start to stink and go bad. If it starts to smell like sewage, it’s time to use it up now or toss it. In time, you will get a pretty good idea of how long ahead to ferment grains.

I keep two or three buckets of a corn/oat mix fermenting, all at different stages. That way, I can use up one before it goes bad, then the next one is more or less ready. With 70 degrees during the day and cooler at night, both cracked corn and whole oats are sweet at 24 hours and souring in about 72 hours.

In hot weather, it goes faster. Keep an eye on it to know where it’s at. Sometimes I add some fresh fodder to the mix. Things like clover, grass, fodder beet and green cornstalk have ended up in my fermenting buckets. I may add some dry hay to the mix too. It all becomes a nice slop that the pigs love.

If your feed is about to go too far before you have a chance to use it all, you can drain it and expose it to air, spreading it out or such. That will stop most of the fermenting action. That way, it doesn’t turn into a bunch of rot.

You can check the doneness by measuring pH. A batch with pH levels of 3.5-4.5 is adequately fermented. The formation of carbonic acid through fermentation makes the mixture acidic. A simple electric pH meter or testing strips will work to check the acidity of the mixture.

Also, cracked or ground grains will ferment more completely than intact, whole grains. Fermenting whole, unprocessed (not rolled, flaked, cooked, or ground) grains is the only way to get pigs to digest them well.

Before large-scale feed processing, fermenting is how hog feed was traditionally prepared. Pigs can fully digest whole corn and whole oats if it has been properly fermented first.

A diet of fermented grains should be offset by some form of vegetation. Reject produce, hay, or fresh wild greens will work. Monitor the animal’s behavior and visible condition to determine how to adjust its overall diet.

Fermented Pig Feed recipes (ratios by dry weight)

  • 18% protein feed (approx)
    • 4 parts corn, 1 part soybean
    • 3 parts corn, 2 parts oats, 1 part soybean.
  • 16% protein feed (approx)
    • 4 parts corn, 2 parts oats, 1 part soybean or pea.
  • 14% protein feed (approx)
    • 6 parts corn, 3 parts oats, 1 part soybean.

*wheat, rye, or barley can be substituted fairly well for oats.

These figures are lower-end averages based on minimum protein content of the grain and normal fermenting conditions as described in this article. These recipes are just a few basic ones, some I came up with and some I’ve heard of elsewhere. Mix the dry ingredients by weight, not volume.

It will vary. For example, corn can vary from 6-9 percent protein with 8 percent being common. I figured the above recipes are based on the minimum, so they should most often come out with higher protein than listed.

Here are the recipes I use

Roasted soybean @ 46 percent protein Corn, fermented @10.8 percent protein

  • 17.8 percent protein
    • 4 parts fermented corn, fermented, 1 part roasted soybean
  • 16.6 percent protein
    • 5 parts corn, fermented, 1 part roasted soybean
  • 14.2 percent protein
    • 6 parts fermented corn, fermented, 1 part roasted soybean
  • 13.6 percent protein
    • 92 percent corn, fermented, 8 percent roasted soybean

If the main protein source (bean/pea) is unprocessed, it should be added before fermentation to make it more digestible. In my case, I just bought roasted soybean. The roasting took place of fermentation to unlock nutrients. If I ferment that, I may actually lose nutrients.

Ground, unroasted soybean will benefit from fermenting. If you want to control how much feed a pig gets, weigh a bucket of mix before and after adding water so you can calculate the difference in weight. Whatever the increase in weight, increase the amount fed by that much to account for water weight.

It’s important to realize that the above recipes are a primary feed, but not a complete feed. Pigs need a varied selection of vitamins and minerals. Our pigs get all theirs from fresh fodder crops like fodder beets, pumpkins, and sunflower heads. They also get wild greens, which they love.

We’re lucky enough to be vendors at the local farmers market and our pigs look forward to the unsellable produce, as well as table scraps from our kitchen. A basic rain/bean diet will give pigs all the energy and protein they need, but they still need to have a varied diet to be healthy.

If you are raising modern market-type hogs then you can go heavy on a grain/protein feed. A lot of the heritage breed pigs don’t need that concentrated of feed and should go heavier on the vegetation. Just watch their body and adjust the feed accordingly. If you have any questions, leave a comment below.

Some good scholarly articles on fermenting feed:

Related Articles on Northern Homesteading:


I practice what I preach. Here in rural west Michigan, me, my wife, and 5 young kids work together to grow food, raise animals, and grow aninmal feed on just 1 acre. I teach homesteading classes locally, and help people where I can.

9 thoughts on “Making Fermented Feed for Pigs (recipies and ratios)

  1. This is a thorough summary and walk-through. Can you talk a bit about how much to feed per hog per day? We are transitioning off of standard powdered corn-soy feed from our local mill, of which our 23-wk-old (almost 2-mo) male pigs were getting each 6 cups per day, as per the recommendation from Storey’s Guide to Raising Pigs. Fermented whole grain and corn feed definitely provides more digestible bulk than the fine powder feed, as well as some of the gas that comes from eating fermented foods. That being the case, do you think we should offer less than the 6 cups per day per pig, or would it be a direct transition? Thanks for your thoughts!

    1. Considering the variation in breeds and sizes, it’s quite hard and not all that usefull to advis on just how much feed to give a pig per day. Modern comercial lines are generally free fed, or just fed multipe times a day untill they don’t want more. Your standard white pigs will eat anywhere from 1/3 pound to 10 pounds dry feed a day, dpending on age and size. I go more by judging the pig’s condition and behavior to see if it’s getting enough feed. For our adult breeders, I give them a less grains and a lot of green fodder to fill their belly without too many calories. from where you are now, I woud start out the same or slightly more by volume, and see if they are acting more hungry than usual or thinning down a bit.

    1. You could. Fermented grains and distiller’s grains are commonly used in dog food. Adding some meat products or meat by-products will make it more appealing to dogs.

  2. I use crushed corn and soybean mill and minerals now could I use peas or what can I use instead of soy? My piglets are about 30 to 40 lbs now how should they be eat and what percent? I have Red wattles pigs

    1. You can use peas. I know of an Amish man who grows lentils for my local feed mill and they use it to make soy-free pig feed and chicken feed. With peas, lentils, and regular shelled beans, they are usually used at nearly twice the ratio that soy is because they’re lower in protein. But, they’re usually higher in overall energy than soy. And, I love the Red Wattle breed. At that size you should be targeting a 16 percent protein feed. Some people like to use an 18 percent feed untuill they are 100 pounds. A functio al starting point is to feed just a little more than they will clean up in one feeding, adn do that twice a day. That’s usually between 3 and 5 percent of their bodyweight worth of feed, daily.

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