In the swine industry, inorganic zinc is commonly fed in high concentrations to nursery pigs to enhance their growth performance and to prevent diarrhea. This results in large amounts of the nutrient in the manure. When spread on fields it can build up faster than crops can use it, can cause nutrient pollution and water quality concerns. A study was done to determine if lower levels of a commercially available organic zinc-polysaccharide supplement would provide growth performance similar to the inorganic zinc typically fed to pigs. The results show that organic zinc supplements can be fed at rates almost 7 times less than inorganic zinc and still maintain pig growth performance and this could also reduce zinc levels in manure by 76%.
This benefit is not without cost as the organic zinc-polysaccharide costs four times as much per pound as the inorganic zinc. However, since less is rationed out, the additional cost is only 9 cents/pig. For large producers already struggling with nutrient issues, feeding pigs organic zinc could be part of an overall nutrient management plan. It is believed that it is only a matter of time before the Environmental Protection Agency begins to regulate zinc and other micronutrients along with nitrogen and phosphorus.
The next step is to identify the molecular pathways in the pig intestines that are responsible for the differences in organic and inorganic zinc uptake. Learning more about these pathways could further improve utilization of zinc, copper and iron, and lessen potential environmental impacts.