Effects of Intraoral, Intracrop, and Intragastric Administration of Copper Sulfate on Vomiting, Retching Behavior,...

Nausea and vomiting are induced by environmental distress and pain; understanding their etiology can improve animal welfare in modern farm operations. Oral administration of CuSO₄ induces nausea and vomiting in some mammalian species and in pigeons. Although oral administration of CuSO₄ induces retching in chicks, whether it causes true vomiting or nausea-like responses remains unknown. This study examined whether intraoral, intracrop, and intragastric administrations of CuSO₄ induced vomiting, retching, and nausea-like responses in chicks (Gallus gallus domesticus). Food intake, crop emptying rate, and voluntary activity were used as indices of nausea-like responses. CuSO₄ limited food intake, irrespective of the administration route, and markedly reduced the crop-emptying rate. Voluntary activity remained unaffected by intraoral administration, but decreased following intracrop and intragastric administrations. Four of the six chicks exhibited retching after intraoral administration of CuSO₄; whereas intracrop and intragastric administrations failed to elicit this behavior. Similarly, CuSO₄ failed to cause any vomiting. These findings indicate that CuSO₄ does not act as an emetic agent in chicks; rather it induces nausea-like responses. Route-dependent effects further suggest that exposure within the oral cavity is required for the excretion of CuSO₄, possibly serving as a protective behavioral mechanism to reject irritant compounds before they enter the lower gastrointestinal tract.