Performance, tissue selenium concentration and glutathione peroxidase activity as response variables for determining selenium requirements of poultry

A total of five experiments were carried out to re-evaluate the selenium (Se) requirement of poultry raised in stainless steel batteries or on litter. Dietary treatments were low Se basal diets supplemented with 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, or 0.35 mg Se/kg diet. In all of the experiments, the basal diets contained 0.04 to 0.06 mg Se/kg diet and adequate vitamin E, by analysis, on an as fed basis. With the exception of Se, the basal diet was formulated to meet or exceed the nutrient requirements of turkeys and broiler chickens as recommended by NRC (1994). With the exception of the 21-day turkey farm experiment, dietary treatments did not affect (P > 0.05) the performance of poultry in any of the experiments. For the 21-day turkey farm experiment, poults fed diets supplemented with 0.10 mg Se/kg diet had higher (P < 0.05) average body weight gain (515 g) compared to poults fed diets supplemented with Se either less than 0.10 or more than 0.15 mg Se/kg Mild pancreatic lesions were observed in 3 out of 6 poults fed diets with no supplemental Se during the 21 days turkey farm experiment. The data were subjected to brokenline analysis to determine requirements. Using tissue Se concentrations and liver and plasma glutathione peroxidase (GPX1 and GPX3) activity as response variables, the requirements were found to range as follows: For poults, raised in stainless batteries for 21 days, the requirements ranged from 0.17 to 0.30 mg total Se/kg diet. For poults raised on litter for 21 days, the requirements ranged from 0.11 to 0.23 mg total Se/kg diet. For poults raised on litter for 42 days, requirements were determined to be 0.15 to 0.29 mg total Se/kg diet. For broiler chicks raised in stainless steel batteries for 21 days, the requirements ranged from 0.11 to 0.31 mg total Se/kg diet. For chicks raised on litter for 21 days, the requirements ranged from 0.14 to 0.29 total Se/kg diet. For chicks raised on litter for 49 days, requirements were determined to be 0.04 to 0.22 mg total Se/kg diet on the basis of tissue Se concentrations. Considering GPX1 as a selenium buffer, the maximum level of GPX1 may not be required, however, maximum concentrations of GPX1 mRNA will confirm the saturation level of the other important seleno proteins. Weiss et al. (1996) reported that GPX1 mRNA concentrations plateaued at half of the dietary Se compared to the Se requirement to attain GPX1 plateau level. Using half maximal levels of GPX1 plus an additional 30% safety margin, it is recommended that poultry diets contain 0.15 mg total Se/kg diet from day 1 to 42 for broiler chicks and day 1 to 49 for turkey poults. Overall, experiments reported here suggests that the requirements listed in the current NRC (1994) for turkey poults (0.20 mg total Se/kg diet) could be reduced to 0.15 mg total Se/kg diet up to 6 weeks of age. However, the requirements listed in the current NRC (1994) for broiler chicks (0.15 mg total Se/kg diet) are adequate up to 7 weeks of age. However, the birds used in experiments reported here were raised under optimal conditions and were from breeder hens fed diets well supplemented with Se.