|Practice tip||Peer reviewed|
Cite as: Jacela JY, DeRouchey JM, Tokach MD, et al. Feed additives for swine: Fact sheets – high dietary levels of copper and zinc for young pigs, and phytase.J Swine Health Prod. 2010;18(2):87–91.
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Copper and zinc are classified as trace minerals because they are required by pigs at relatively low levels for normal growth.
When added at high dietary levels, copper (100 to 250 ppm) and zinc (2000 to 3000 ppm) can increase the growth performance of young pigs.
The mechanisms by which high levels of copper and zinc improve growth rate in pigs is still unclear.
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.1 In addition, copper is efficacious even when antibiotics also are included in the diets.2 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.3
Zinc fed at high dietary levels (2000 to 3000 ppm) reduces incidence of diarrhea and increases weight gain in newly weaned pigs.4,5 However, these high levels of dietary zinc are beneficial to pigs only during the early phases of the nursery period.6 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.6
Mode of action for growth promotion at high dietary levels
The mechanism by which high levels of copper and zinc improve growth rate in pigs is still unclear. Both have some antibacterial properties,9 which may explain the growth-promoting effect, but there is a lack of scientific evidence to understand the exact mode of action. The improvement in growth performance when the diet is supplemented with high levels of dietary copper is similar in magnitude to that achieved when in-feed antimicrobials are fed to nursery pigs.2 Even though copper has antibacterial properties, growth rate is stimulated in an additive manner when both antimicrobials and high levels of copper are added to nursery pig diets.2 Thus, it appears that the growth-promoting properties of high dietary levels of copper are in addition to its antimicrobial effect.
What are the sources used for growth-promoting levels of copper and zinc?
Most research on high levels of dietary copper has used copper sulfate.10 Increased growth rate has been demonstrated with the tri-basic chloride form as well.11 Limited information is available using other sources.
Increased growth rates when high levels of zinc are fed in the early postweaning period have been most consistently demonstrated with zinc provided as zinc oxide.4,8,12 Other sources, such as zinc sulfate and zinc methionine, have not consistently demonstrated positive effects.12,13
What are the potential problems with adding copper or zinc at these very high levels?
Copper toxicosis may occur when dietary levels exceed 250 ppm for long periods.10 Jaundice (yellow discoloration of the skin) may result due to excessive accumulation of copper in the liver. Toxic effects of zinc, on the other hand, may be indicated by depressed pigs, arthritis, gastritis, and death. Zinc toxicosis has been reported when highly absorbable zinc sources, such as zinc carbonate, are added at up to 4000 ppm for an extended period.10 To avoid these problems, it is important to use only the recommended dietary levels of copper and zinc for growth promotion at specific growing periods (Table 1).
Table 1: Recommended dietary levels of zinc and copper for pigs
* Growth-promotion levels.14
† Based on National Research Council minimum daily requirement.10
‡ Growth-promotion levels.3
It is also important to keep in mind that as more of these nutrients are added to the diet, the amount excreted by the animal also increases. Thus, the addition of copper and zinc at their growth-promoting levels can have negative repercussions in the environment because of high levels of these minerals being excreted through the feces,15,16 with resulting excessive accumulation of copper and zinc in the soils where the manure is applied.
Another negative effect of high dietary levels of copper is that the amount of unsaturated fat is increased, which results in a softer pork fat.17 Reducing dosages in finishing diets can minimize these negative impacts.
Copper and zinc are important trace minerals needed by the pig for numerous metabolic functions. Inclusions of these trace minerals at high dietary levels increases growth performance, especially in young pigs.
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10. National Research Council. Minerals. In: Nutrient Requirements of Swine. 10th ed. Washington, DC: National Academy Press; 1998:47–70.
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17. Pettigrew JE, Esnaola MA. Swine nutrition and pork quality: A review. J Anim Sci. 2001;79(E-suppl):E316–E342