Copper and zinc play important roles in many physiological
processes. Dietary copper levels of 5 to 10 ppm and zinc levels of
50 to 125 ppm are generally enough to meet the pig’s nutrient
requirement for these processes. However, when supplied at high
concentrations (100 to 250 ppm for copper and 2000 to 3000
ppm for zinc), these two minerals are known to exert positive
influences on growth rate. In addition, copper is efficacious even
when antibiotics also are included in the diets. This suggests
that the response to copper is additive to the response to antimicrobials.
Response to high levels of dietary copper decreases with
increasing age and with longer periods of administration.
Zinc fed at high dietary levels (2000 to 3000 ppm) reduces
incidence of diarrhea and increases weight gain in newly weaned
pigs. However, these high levels of dietary zinc are beneficial
to pigs only during the early phases of the nursery period. Thus,
feeding period for high dietary levels of zinc should be limited to
approximately 3 weeks after weaning. Additive effects are usually
not observed in weaned pigs when high levels of copper and zinc
are added together. However, the data is conflicting and this observation
needs to be further investigated.4,6-8 Recent research has
indicated that feeding high levels of zinc until pigs reached 12 kg,
then feeding high levels of copper for the remainder of the nursery
period, was the most cost-effective strategy. Pigs need dietary phosphorus for normal body maintenance and
growth. It is an essential element that is required in many physiological
processes in the pig’s body and thus suffi cient amounts
must be included in the diet. This element is abundant in most
grains found in swine diets. However, only a small amount of
phosphorus is utilized from grains, because the majority of the
phosphorus exists in a form (phytate) that is not digestible in
swine. The digestibility of phytate phosphorus can be increased
when supplemental phytase is included in the diet.
