“Performing pigs” might sound like entertainment, but maximizing pig performance is serious business for producers. Just as a healthy diet keeps people going strong, the right amount of vitamins and minerals in pig feed can be the difference between profit and loss in the pork sector. Towards that end, researchers went to work on micronutrient strategies to maximize robustness and performance for pre- and post-weaning piglets.

Science has known for years that piglets are prone to iron deficiency. Although they are born with reasonable iron levels, they can begin to run low on this mineral by day 3, and will become anemic by weaning if they aren’t given iron supplements. So what happens with other trace minerals and vitamins?

Curious copper

Copper is an essential mineral for pigs, as it improves growth performance and feed conversion rate, especially in young pigs. While the National Research Council Canada recommends 6-10 ppm (parts per million) in the diet of postweaning pigs, the industry standard in Canada is 130 ppm on average. Through blood sampling in a previous study, researchers determined that copper levels decreased in the post-weaning period to very low values usually found at birth, even in animals given large amounts of copper. In spite of providing pigs with up to 20 times the suggested amount, they still emerged as copper deficient three weeks after weaning.

The results with copper prompted a highly scientific question: “What the heck happened?”

Let’s think about zinc

In search of an answer, scientists then added zinc to the mix, which is still used in high doses to prevent diarrhea in pigs in Canada. Experimenting with different levels of copper sulfate and zinc oxide supplementation, they found that large amounts of zinc (3000 ppm) stimulated an enzyme that trapped copper in the intestinal tissue. By not allowing copper to reach its intended destination of the liver and serum (the fluid component of blood), this enzyme caused pigs to become copper deficient.

Ironing out some issues

Another crucial mineral for pigs is iron, as it is essential for optimal health and growth. In spite of iron supplementation in the first week of life, recent research shows that piglets may be iron-deficient at weaning. Although post-weaning diets are rich in iron, again, high levels of zinc oxide proved problematic, impairing the building up of iron reserves in the liver.

From hazard to helpful

By exploring the effects of various mineral levels on piglets, researchers have begun homing in on the ideal supplement regimen to promote growth and performance. This quest is vital in light of developments in the industry. In 2021, the Canadian Food Inspection Agency (CFIA) consulted with the pork sector to better understand the effects of zinc and copper and propose new levels of supplementation with these minerals. Of particular concern to the CFIA is that high levels of zinc can be harmful to the environment when it is excreted in manure and spread on farmers’ fields. This may lead to a high concentration of zinc in the soil will remain for up to 50 years before fully dispersing, preventing crops from growing properly in that field. Zinc can also be a public health concern, as it stimulates the expression of some genes in bacteria that make them more resistant to antibiotics.

In 2022, the European Union banned the use of high zinc levels for pigs, and Canada appears headed in the same direction. The latest recommendation from the CFIA is to lower zinc limits from 3000 ppm to 300 pm. Once this change becomes mandatory, producers will have lost two of their greatest weapons for preserving pig health: antibiotics and zinc oxide. As farmers try and adapt to new regulations, studies like this are crucial to properly supplementing with minerals such as zinc and copper. From a scientific standpoint, if you don’t know what happens to pigs when given both high and low levels of minerals, how can you properly adjust feed to meet the new standards without compromising piglet health and growth?

Maintaining your balance

Because of the negative interactions between zinc and copper, a low dietary zinc-to-copper ratio may improve the absorption and utilization of both minerals. However, this study also showed that low levels of both copper (6 ppm) and zinc (100 ppm) appear not to fulfil the piglets’ requirements for these minerals during the first weeks post-weaning. That shortfall points to the need for a better understanding of zinc and copper nutrition for post-weaning piglets.

Ultimately, a balanced, holistic approach, considering pig health, nutrition, performance and the environment, will enable the animals to express their full potential while safeguarding humans and the planet.

Backed by funding from Swine Innovation Porc, this study drew on expertise from several organizations. These included DSM Animal Nutrition & Health, Lallemand Animal Nutrition, Agri-Marché, and the Deschambault Animal Science Research Centre (DASRC) of Agriculture & Agri-Food Canada (AAFC).

As always, a number of scientists brought their knowledge to the project: Drs. Jérôme Lapointe, Guylaine Talbot, Danyel Bueno Dalto, Jacques Matte (research scientist – retired) and Martin Lessard (research scientist – retired), all with AAFC in Sherbrooke, Quebec; Dr. Frédéric Guay, professor, Faculty of Agricultural and Food Sciences - Department of Animal Sciences at Université Laval; and Ms. Yan Martel-Kennes with (DASRC).

Looking ahead, the researchers will further study the interaction between zinc and copper sources, both organic and inorganic, and examine the effects of mixing, such as inorganic zinc and organic copper, and vice versa. They will also experiment with different supplementation timings, as well as various delivery methods, such as through drinking water, to see if that increases absorption and reduces the negative interactions between minerals.

Links to publications:

Effects of supranutritional levels of dietary zinc oxide on zinc, copper, and iron metabolism in post-weaned pigs. J Anim Sci. 2020; 98, Issue Supplement_3, p.106–107, https://doi.org/10.1093/jas/skaa054.181

Effets des niveaux d'oxyde de zinc dans l’aliment des porcelets en post-sevrage sur le métabolisme du zinc, du cuivre et du fer. Journées Recherche Porcine 2021; 53, 237-238.

Effects of dietary zinc/copper ratios on the metabolism of zinc, copper, and iron in weaned pigs. Animal - science proceedings 2022; 13, Issue 2, p.184. https://doi.org/10.1016/j.anscip.2022.03.291

Effects of dietary zinc oxide levels on the metabolism of zinc and copper in weaned pigs. J Anim Sci. 2023;101:skad055. doi: 10.1093/jas/skad055.