Now that zinc oxide is being replaced by other products in many regions, copper sulfate could make a comeback.
Copper sulfate was the additive of choice for post-weaning piglet feeds. It controlled diarrhea and improved feed intake and growth performance. It was largely replaced by zinc oxide, which had a stronger effect on similar parameters during the early post-weaning period. Now that zinc oxide is being replaced by other products in the EU and many other regions, I see the good old copper sulfate making a strong comeback. The EU has a limit on the amount of copper one can add in a piglet feed (150 ppm), but other regions/countries do not have such legislation in place.
Lately, I have seen many piglet feed manufacturers bringing back copper sulfate at 250 ppm copper (not copper sulfate) in the final feed. This was the recommended dosage in pre-zinc-oxide times. However, we must keep in mind that 250 ppm copper is the toxicity limit and toxicity is a dose-related effect, meaning it is affected by feed intake. And, we should also account for the fact that this level of 250 ppm copper in the final first-phase feed post-weaning was established decades ago when feed intake during this period was much lower than today. Presently, we do not have updated recommendations concerning modern feed designs that allow for greater feed intake, hence greater ingestion of copper.
In fact, zinc toxicity was observed in several cases with super-dosing zinc oxide at 3,000 ppm zinc (not zinc oxide). This was because the toxicity level for zinc is 1,000 ppm, this high level was kept until pigs were 70 days old (well past the phase they actually needed this pharmacological dose of zinc from zinc oxide) and when feed intake was exceptionally high due to high-quality and well-balanced feed designs. The same is very likely to happen now with copper sulfate.
So, when bringing back copper sulfate in your piglet feeds, please consider any possible toxicity implications, especially if your feeds support high feed intake post-weaning.
