ISSUE FOCUS 24 FEED & ADDITIVE MAGAZINE July 2022 "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." Copper (Cu) at high dietary levels has been used for a long time as a growth promoter in different production animals. Two possible modes of action have been proposed: a pre (antimicrobial and local) and a post (systemic) absorption effect. In the feed, Cu is usually provided as a sulphate source (CuSO4), although other sources are also available. Increasing CuSO4 supplementation to supra nutritional levels is well recognized to significantly enhance the growth performance of piglets, as shown in the Figure 1 where the improvement in body weight (BW) is of 3.4 kg when 160 mg/kg of Cu are compared to 15 mg/kg. HYPOTHESIS OF PRE-ABSORPTION EFFECT OF Cu The antimicrobial effect has been recognized since Ancient Egypt, where Cu was used to sterilize chest wounds and drinking water. In the pig, this antimicrobial effect would occur once dietary Cu passes through the stomach, dissociated into Cu ion, and reaches the intestine in its ionic form. Some authors reported that the supplementation of high Cu (250 ppm from CuSO4) reduced the cecal Enterobacteriaceae population by 23% and improved the average daily gain in piglets by 37% when compared to a basal diet. The improvement in pig performance following supra nutritional addition of Cu in the diets was also observed in a recent feeding trial performed at Wageningen University & Research (WUR) with 200 weaned piglets. Copper was supplemented from CuSO4 at two levels (15 or 160 ppm) in the diets. The significant increase in the final BW by Cu supplementation was accompanied by a decrease in E. coli population in the colon (Figure 2). These results suggest that prior to absorption, high levels of Cu reduce bacterial populations, resulting in a positive modulation of the intestinal microbiota. Other studies have also shown that high Cu dosages by CuSO4 supplementation significantly inhibited potential pathogenic coliforms in the cecum and the colon of piglets. COPPER METABOLISM AND GROWTH PROMOTION: IS THERE A RELATION? Alessandra Monteiro R&D Animine
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