Abstract
This study was conducted to determine the solubility of copper (Cu) in two sources of copper(II) sulfate (CuSO4) including monohydrate and pentahydrate and three sources of dicopper chloride trihydroxide (dCCTH) including α-form (dCCTH-α), β-form (dCCTH-β), and a mixture of α- and β-form (dCCTH-αβ) at different pH and a 3-step in vitro digestion assay for pigs. In Exp. 1, Cu sources were incubated in water-based buffers at pH 2.0, 3.0, 4.8, and 6.8 for 4 h using a shaking incubator at 39°C. The CuSO4 sources were completely dissolved within 15 min except at pH 6.8. The solubility of Cu in dCCTH-α was greater (p<0.05) than dCCTH-β but was not different from dCCTH-αβ during 3-h incubation at pH 2.0 and during 2-h incubation at pH 3.0. At pH 4.8, there were no significant differences in solubility of Cu in dCCTH sources. Copper in dCCTH sources were non-soluble at pH 6.8. In Exp. 2, the solubility of Cu was determined during the 3-step in vitro digestion assay for pigs. All sources of Cu were completely dissolved in step 1 which simulated digestion in the stomach. In Exp. 3, the solubility of Cu in experimental diets including a control diet and diets containing 250 mg/kg of additional Cu from five Cu sources was determined during the in vitro digestion assay. The solubility of Cu in diets containing additional Cu sources were greater (p<0.05) than the control diet in step 1. In conclusion, the solubility of Cu was influenced by pH of digesta but was not different among sources based on the in vitro digestion assay.
Highlights
Copper (Cu) is essentially required for pigs to serve many functions in the body such as enzyme activations, immune functions, and hemoglobin synthesis (Hill and Spears, 2001)
Previous studies suggested that growthpromoting effects of dietary Cu might be attributed to both antibacterial properties (Højberg, 2005; Namkung et al, 2006) and systemic actions (Zhou et al, 1994)
Zevenhuizen et al (1979) reported that the growth of Cu-sensitive bacteria including Escherichia coli B, Klebsiella aerogenes H, and Alcaligenes Ad-4 was inhibited in Cu-containing media in which Cu ion was derived from CuSO4 and ranged from 0.06 to 0.6 mg/kg
Summary
Copper (Cu) is essentially required for pigs to serve many functions in the body such as enzyme activations, immune functions, and hemoglobin synthesis (Hill and Spears, 2001). Many studies have reported that pharmacological concentrations of Cu in diets, ranged from 100 to 250 mg/kg, improved growth performance of weanling pigs (Cromwell et al, 1998; Hill et al, 2000; Veum et al, 2004; Pérez et al, 2011; Shelton et al, 2011) and growing pigs (Cromwell et al, 1978; Zhao et al, 2014). Many studies have been conducted to determine the possible mechanisms for growth-promoting effects of dietary Cu. Højberg et al (2005) and Namkung et al (2006) suggested that pharmacological concentration of dietary Cu reduced population of pathogenic bacteria in the gut and subsequently increased the growth performance of weanling pigs. Whether dietary Cu improves the growth performance by affecting the condition of gastrointestinal tract, by promoting the systemic action, or both, liberation of Cu from the compound is critical to elucidate its growth-promoting mechanisms in pigs, which may be partially explained by in vitro solubility
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