What happens when you use high doses of Zinc Oxide (ZnO) in the weaning feed for piglets?

Many farmers would answer “Less diarrhoea”, which is correct, but few know that it damages the immune system and causes inflammation.

Through a microscope, you will see why.


We aim to produce healthy piglets ready to digest solid feed at weaning. For a gut to be healthy and functional, the piglet needs a well-developed gut architecture, a tight and thick gut barrier and a diverse and healthy gut microflora. You can see the difference between a healthy and unhealthy gut in the illustration below. A healthy gut protects the bloodstream from pathogens, while the leaky gut allows pathogens to enter the bloodstream.


Zinc Oxide increases the gut bacterial composition’s diversity and helps develop the villi responsible for nutrient utilisation.

If you look at the images below of the piglet gut ten (days after weaning), you will see how different feed affects the gut.

In image 1, the pig is fed soy protein concentrate (SPC) without Zinc Oxide.

In image 2, 2,500 ppm Zinc Oxide is added to the soy feed.

Image 3 shows the piglet gut when fed with a diet with soy protein (SPC), 10% fermented rapeseed (EP100i) and no Zinc Oxide.  The images show the microstructure of the small intestine.

Image 1: Feeding of soy protein concentrate (SPC) without zinc oxide, resulting in an underdeveloped gut with short villi. In image 2 the SPC and 2.500 ppm zinc oxide have increased the villi’s length. The villi are loosely packed and the bloodstream unprotected against invading pathogens. The piglet in image 3 is fed with SPC and fermented rapeseed without zinc oxide. As you can see, the villi are long, and the junctions are closely connected. As a result, the piglet is much better guarded against pathogenic bacteria migrating into the bloodstream.


The piglets use energy to fight inflammation. As a consequence, they grow less,  become more susceptible to infections, and some stop eating as well. That’s why it is essential to maintain inflammation levels as low as possible.

Inflammation can be evaluated on a scale from 0 to 3, 0 indicating no inflammation and 3, a sign of severe inflammation.

Take the examples above, where piglets are fed diets with or without zinc oxide. On the charts, you can see that both piglet groups fed SPC with (Green) and without Zinc Oxide (GREY) suffer from moderate to severe inflammation. The third group (BLUE) consisting of SPC+10% fermented rapeseed and no zinc oxide has the lowest inflammation degree.

The fermented rapeseed group (BLUE) experienced fewer complicated incidences of diarrhoea.

Diagrammes: Shows intraepithelial and stromal lymphocyte infiltration in small intestine and colon in the three treatment groups: SPC (basal group) without Zinc Oxide, the Zinc group with SPC + 2,500 ppm Zinc Oxide and the EP100i group with SPC + 10% fermented rapeseed (EP100i) without Zinc Oxide. Lymphocytes are immune cells circulating in the blood to fight and destroy invading bacterial and viral pathogens. The more lymphocytes, the higher the degree of inflammation. Enterocytes ensure nutrient absorption in the piglet gut and should be present in large numbers.

Diagrammes 1 and 2 show increased infiltration of intraepithelial lymphocytes in the basal (SPC GREY bar) and zinc group  (SPC+2500 ppm ZnO GREEN Bar) indicating sub-clinical inflammation with moderate to severe damage to the intestinal epithelial barrier. Piglets fed fermented rapeseed (EP100i) had a significantly lower degree of inflammation than the diets containing soy protein concentrate with and without Zinc Oxide.  


Sow feed: Weaning feed affects piglet intestine health, but if you look at the bigger picture, the sow is responsible for most of its health. Through the gestation period and during lactation, you can influence and promote gut development and the piglet’s immune system through the sow feed.

If you want to more about how fermented sow feed can contribute to successful weaning, take a look at the sow feed EP199 here.

Piglet feed: If you want to focus specifically on zinc-free weaning feed solutions, we suggest you start by evaluating your farm’s health status. If it is very high, you might be able to phase out Zinc Oxide without further ado. Remember to test on a small group of piglets first.

If you need Zinc Oxide’s gut modulatory effect without harming the immune system, we suggest using the fermented rapeseed feed EP100i.

If you want to know more about our zinc-free and antibiotic-free rearing, then please contact us or enter your information in the form below. It is free and non-binding.

A large-scale trial conducted on piglets fed with soy protein concentrate, soy protein concentrate added 2,500 ppm Zink Oxid or soy protein concentrate added 10% EP100i. Copenhagen University did the trial.
See the data here.