ISSUE FOCUS FEED & ADDITIVE MAGAZINE July 2022 27 main roles of bile are to enhance the fat digestion and absorption as well as the excretion of metabolic waste products from the organism. As around 80% of the absorbed Cu is excreted in the bile, a post absorption antimicrobial activity of Cu has been raised by some authors. It has been reported that the Cu in the bile is in the form of nonabsorbable-stable copper chelates. Biliary Cu recycling can be thus, considered negligible and being mostly excreted in feces. Besides, the Cu excreted by the bile (considering the Cu concentration and the bile flow during 28 days) represents less than 0.1% of total Cu intake, so it can be suggested that biliary excreted Cu would not have the same antimicrobial impact on microbiota as the dissociated Cu ion after ingestion. A recent study conducted in the United States, has shown that nursery piglets fed 250 mg of Cu/kg from CuSO4 present an improved feed efficiency compared to those fed 5 mg of Cu, but without differences on inhibitory action of bile against Salmonella, E. coli or Enterobacter populations. Another trial performed at University of Illinois with high levels of Cu showed that the hepatic Cu accumulation is not related to its effect on pigs performance. The increase of Cu supplementation from 125 to 250 mg/kg of Cu from CuSO4 for fattening pigs resulted in higher hepatic Cu accumulation, so it can be expected to have a high Cu exportation in the bile. However, after 133 days of trial, final BW did not increase accordingly (Figure 3). Although a plateau in the growth rate of finishing pigs was observed when Cu levels in the feed exceed 100 mg/kg, Cu accumulation in the liver showed a dose response behaviour. The storage of Cu in the liver is a consequence of Cu intake and not the cause of its growth promoter effect. Besides, the long-term feeding with high Cu levels leads to an excess of Cu in the organism, which can cause cellular damage through the formation of free radicals and this may induce oxidative stress. PRE VS POST ABSORPTION HYPOTHESES According to recent studies, copper metabolism seems to be not related to growth promotion. The strongest hypothesis is that its effect seems to be related to microbiota modulation resulting in the improvement of gut health, but not to Cu accumulation in the liver. Thus, a more antibacterial copper source might be more efficient to promote growth. The effects of Cu in killing bacteria differ according to its redox state: the Cu(I), the reduced cuprous form, has a stronger antibacterial effect in anaerobic conditions than Cu (II), the oxidized cupric form. A red source of monovalent copper (CoRouge®, Animine) has shown improved pig performance and a strong antibacterial effect, with lower risk of animal toxicity. About Dr. Alessandra Monteiro Dr. Alessandra Monteiro is an animal scientist working within the R&D team of Animine. Her main expertise is the sustainable usage of trace minerals in monogastric nutrition. High Concentration Flowability Safety standards Stability Bioavailability Animal performance POTENTIATED ZINC POTENTIATED ZINC MONOVALENT COPPER HIGHLY PURIFIED MANGANESE an international and independent supplier of precision minerals , www.animine.eu
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