Why are controlling minerals important?

Questions about the long-term use of copper, zinc, and sodium have also been raised regarding soil toxicity and ground water safety. In the past, these nutrients were added to animal diets at concentrations sufficient to provide a margin of safety. Modern inclusions much more accurately match mineral levels in the feed with animal needs. Copper and zinc are sometimes added to the diet at levels which greatly exceed the nutrient requirements of the pig. High concentrations of both copper (up to 250 ppm) and zinc (up to 3000 ppm) have been shown to enhance growth performance and feed efficiency, especially in young pigs. However, these concentrations should not be fed to pigs weighing more than 45 pounds. Older pigs consuming high levels of copper and zinc do not respond ass well, and they have a higher feed intake, which will contribute to more excretion and increased trace elements in the soil. High concentrations of trace elements do not appear to result in higher mineral uptake by crops such as corn and soybeans. However, in the case of vegetable crops for human consumption, near-neutral pH must be maintained to prevent abnormally high trace element uptake.