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Are You Using the Right ZINC Source for your Pigs?

by Emily Angeles

Zinc (Zn) is considered an important micro-nutrient because of its vital roles in many biochemical processes. It is involved in over 200 enzymatic reactions in the body.

Zn from the compound zinc oxide (ZnO) is widely utilized in the Philippine livestock and poultry industry. It is used nutritionally as source of Zn and at pharmacological dosage to address post weaning diarrhea and ensure gut health in growing pigs. Studies show that pharmacological dosage of Zn at 2,000-3,000 mg/kg, which is around 2.7 to 4.0 kg/MT of ZnO, enhances growth and health of nursery pigs.However, the quality, form and duration of feeding, post questions to some users. 

Quality of ZnO is primarily dependent on source. Processing conditions such as high temperature can bring about chemical instability. Depending on the Zn form, duration of feeding and ZnO intake, growth of animal may suffer as a result of gastro-intestinal distress, anemia, abnormal bone and joint health and impaired enzyme function.

Aside from possible toxicity, recent studies showed that low quality ZnO batches may have very high levels of toxic heavy metals such as Cadmium(Cd) and Lead (Pb). These toxic metals sometimes mimic the action of an essential element or nutrient in the body, interfering with the varied metabolic processes, causing illnesses or organ dysfunctions. An example of this is the estrogenic effect of heavy metals that brings about abnormality to the reproductive system which lowers efficiency of breeding animals.In humans, elemental Cd and Cd-containing compounds are known carcinogens.Long-term exposure to low levels of these toxic metals leads to buildup in tissues that could cause kidney disease, lung damage and fragile bones. On the other hand, Pb is also a probable human carcinogen and can also affect several metabolic processes.

Recently, analysis of ZnO samples utilized in pig diets in Thailand showed Cd and Pb contents way beyond tolerable limits. Cd contents range from 434 ppm to 862 ppm vs. the acceptable EU limits of only 30 ppm. Pb analysis results yielded levels of 1,938 ppm to 14,400 ppm vs. the acceptable EU limits of only 400 ppm. Based on EU regulations, heavy metal contents of these ZnO samples are 15 to 30 times and 5 to 35 times higher for Cd and Pb, respectively. The level of contamination of these ZnO batches can be related to an analytical survey of pig kidneys (Figure 1). Twenty-eight (28%) percent of the kidney samples contained concentrations above international standards for human consumption. Dietary sources include macro-ingredients and mineral premixes that utilize mineral compounds that could be contaminated with the heavy metal Cd.

Figure 1. Cadmium concentration in kidneys(individual results in red > 1 mg/kg, maximum regulatory values)

Animals can tolerate high levels of Cd in their diet thus resulting to accumulation in the animal tissues primarily kidney and liver. The possibility of heavy metal contamination in carcasses is a clear area of concern for human health. Consequently, maximum dietary levels in the feed of animals used for human food should be set on the basis of human health and not animal health. In addition, heavy metals are not degraded or lost. It is only a question of time until a level is reached where it can affect not only animals but humans and the environment.

Alternative source of Zn especially ZnO can help reduce above risks to animal and human health. HiZox®, a potentiated feed grade ZnO, has been designed for specific usage in animal nutrition. The patented manufacturing process of HiZox® results in the enhanced purity and guarantees lower concentration of heavy metals such as Cd and Pb.

References: Available upon request