The article presents, interprets, analyzes and examines legal obligations of veterinary surgeons who conduct animal examinations, issue decisions on animal health, and prepare opinions in connection with the contract of sale. It examines responsibilities originating from various sources and forming a complex system of relationships. A veterinary surgeon has numerous obligations in the field of civil law (including general civilian rules and norms of the law of obligations) and corporate law (including ethics and professional deontology). Moreover, he also has specific documentation, information, and explanatory duties closely related to the contract. The liability threshold of a veterinary surgeon is very low, which applies in particular to the mixed contract discussed here (an obligation of due diligence in relation to examination and an obligation of result in relation to decision-making).