Impact of dietary manganese concentration on status criteria to determine manganese requirement in piglets

The Mn requirement for pigs is not well established. This study aimed to find criteria for assessing growing piglet supply status for Mn and to determine whether the current Mn recommendations meet the requirements for piglets. Thirty-six weaned male castrated 27-day-old piglets (7.24 +/- 0.69 kg) were randomized into six groups of six piglets each and housed individually in stainless steel metabolic cages for 42 days. The piglets were fed a diet based on skimmed milk powder and corn starch with increasing Mn concentrations (0.24; 2; 4; 8; 16; or 32 mg Mn/kg diet as-fed). In week 6, Mn0.24 led to reduced feed intake (p < 0.05). Manganese concentrations in blood, liver, kidney, lung, heart, phalanx proximalis, pancreas and skeletal muscle were influenced by the dietary Mn supply (p < 0.05). The activity of the Mn-containing superoxide dismutase in the heart as well as relative arginase activity in the liver were lower in groups Mn0.24, Mn2 and Mn4 compared with the higher supplemented groups (p < 0.05). The relative arginase activity increased clearly with enhanced dietary Mn up to 16 mg/kg and correlated with Mn concentration in the liver. Manganese concentrations in the liver, kidney and phalanx proximalis seem to be suitable biomarkers for Mn status. A 4 mg/kg dietary Mn concentration recommended by NRC (1998, Nutrient Requirements of Swine. National Academy Press, Washington DC.) did not fulfil piglet requirements. Under the conditions investigated, 16 mg Mn/kg diet were necessary to reach a plateau in specific enzyme activity and Mn concentration in organs.