Objectives: Formaldehyde (HCHO), besides being an excellent anti-microbial agent, is also a toxic chemical and, as such, can seriously damage. Formaldehyde is a gas at room temperature and it is readily soluble in water. The formaldehyde solution was frequently used in poultry; however the non-adequate can use to be producing toxic in birds. The objective of this work was carried out to determine the toxic effect of a formaldehyde solution on laying hens that were given formaldehyde in different doses in water. Materials & Methods: We were formed four groups of 15 layer hens of 28 weeks of age and the solution was tested in the drinking water at a dose of 1.5 ml / l; 2 ml / l; 5 ml / l; 10 ml / l and was applied it directly to the crop through an esophageal tube, at a rate of 25 and 50% diluted in water. Results: We obtained as results that doses of up to 2 ml / l were not toxic; however, higher doses reduced the consumption of water and food, causing a stress that caused a decrease in egg production and affected the health status of the birds. Birds treated with small doses did not show symptoms consistent with the intoxication, while those of the third trial in which formaldehyde was applied by means of a tube, presented sadness, drowsiness, cyanosis with edema in the crest and barbells, and two deaths occurred. Conclusion: The state of the excrete material was affected when higher doses than 2ml / l were applied and in all of which the product was applied consecutive days, showed solid or semi-solid stools with a remarkably low water content, while urate concentrations were high.
