In this study brand loyalty of pharmaceutical livestock products among commercial farmers was measured. The purpose of the study was to assist agribusinesses to identify the dominant determinant when commercial farmers purchase pharmaceutical livestock products from them. A structured questionnaire was used to employ an empirical study in a quantitative style to determine the commercial farmers’ perceptions and buying behaviour when they buy pharmaceutical livestock products. The results indicated that the data were reliable. It also indicated that no practical significant differences existed between the four categories of pharmaceutical livestock products exist which means that these product categories could be managed similarly with regard to brand loyalty. All twelve the brand loyalty influences are regarded to be important. The influences Customer service, Brand performance and Brand trust are the three most important influences.