Tolerance and safety evaluation of sodium sulfate: A subchronic study in laying hens.

Sodium sulfate (NaSO) is a readily available chlorine-free source of sodium, which could be used to reduce sodium chloride to maintain the ratio between chlorine and sodium in poultry diets. Dietary supplementation with excessive levels of NaSO might be detrimental to bird's health and performance. A subchronic study was carried out to investigate the potential adverse effects of an accidental oversupply of NaSO in the diets of laying hens. Four hundred and fifty 21-week-old Hy-Line White layers were randomly assigned to 5 treatments with 6 replicates. The birds were fed diets supplemented with 0 (control), 0.3%, 0.6%, 1.5%, and 3.0% NaSO for 8 weeks. Laying performance, egg quality parameters, clinical blood parameters, histopathology, intestinal barrier functions, and intestinal microflora composition were measured. No clinical signs of intoxication or mortality were observed during the experimental period. The results of this study showed that the optimal levels of NaSO (0.3% to 0.6%) significantly improved the laying rates, average daily egg mass, and eggshell quality of hens compared to the control ( < 0.05). However, 3.0% NaSO produced negative effects on laying performance, eggshell quality, blood biochemistry, and particularly on liver and kidney pathology, and intestinal morphology and barrier functions compared with the controls. Although minor changes were observed in clinical blood parameters of hens receiving 1.5% NaSO, these were not considered to be of toxicological significance due to the absence of any organ pathological changes in hens. In conclusion, our results indicated that a NaSO concentration of 1.5% was non-deleterious to laying hens after a daily administration for 56 d, namely that dietary supplementation of up to 5 times the maximum recommended dose is safely tolerated by laying hens.