Bioavailability of organic manganese sources in broilers fed high dietary calcium

Abstract

A total of 624-day-old Arbor Acres male broilers were used to investigate the relative bioavailabilities of supplemental organic manganese sources for broilers fed high calcium diets. The broilers were randomly allotted to six replicate cages (eight chicks per cage) for each of 13 treatments in a completely randomized design involving a 4×3 factorial arrangement of treatments (four sources of Mn×three levels of added Mn, plus the control with no added Mn). Dietary treatments included the high calcium basal diet (the Control, containing 18.5 g Ca/kg and 20 mg Mn/kg) and the basal diet supplemented with 60, 120, or 180 mg Mn/kg as Mn sulphate (MnSO 4·H 2O) or Mn methionine E (Mn Met E) with weak chelation strength [formation quotient ( Q f) = 3.2, containing 82.7 g Mn/kg], Mn amino acid B (Mn AA B) with moderate chelation strength ( Q f = 45.3, containing 64.8 g Mn/kg), or Mn amino acid C (Mn AA C) with strong chelation strength ( Q f = 115.4, containing 78.6 g Mn/kg). Heart manganese-containing superoxide dismutase (MnSOD) mRNA level and heart Mn concentration increased as supplemental dietary Mn increased ( P<0.001). Heart MnSOD mRNA level ( P=0.020) was a more sensitive criterion than heart Mn concentration ( P=0.037) for detecting differences among Mn sources. Relative to Mn sulphate (assigned 1), bioavailability of the three organic Mn sources with weak, moderate, or strong chelation strength were 1.12, 1.45, and 1.48 for heart MnSOD mRNA level, respectively. Compared with the study with normal dietary calcium (relative bioavailability of the above three organic Mn sources were 0.99, 1.32, and 1.13 for heart MnSOD mRNA level if Mn sulphate was set as 1, respectively), the results herein show higher relative bioavailability, implying that organic Mn sources with moderate or strong chelation strength offer partial or complete resistance to interference from high dietary calcium during digestion.