Analysis of quality and antibiotic residues in raw milk marketed in the Chaco Province of Napo, Ecuador

Abstract

Abstract Milk quality monitoring is essential to guarantee food safety and identify factors affecting the physicochemical characteristics of dairy products. This study aimed to evaluate the physicochemical quality and detect antibiotic residues in raw milk marketed in El Chaco Canton, Napo Province, Ecuador. A total of 500 raw milk samples were collected from 32 farms distributed across seven productive sectors during four sampling periods. Milk composition parameters, including fat, protein, lactose, and non-fat solids, were determined by infrared spectrophotometry. Somatic cell count (SCC), Dornic acidity, alcohol stability, and qualitative detection of β-lactam, sulfonamide, and tetracycline residues were also evaluated. The results showed that fat (4.38 ± 1.63%), protein (3.05 ± 0.51%), lactose (4.57 ± 0.66%), and SCC (5.65 log10; 448,252 cells/mL) values were within the ranges established by Ecuadorian regulations. Significant differences among productive sectors were observed for non-fat solids, density, Dornic degrees, and SCC (P < 0.05), suggesting variability associated with production conditions, feeding management, and animal health status. Lactose concentration and SCC showed significant differences among sampling periods, indicating temporal variation in milk composition and udder health indicators. Antibiotic residues were detected in 1% of the analyzed samples; however, these results should be interpreted as screening findings that require confirmation through quantitative analytical methods. Overall, raw milk marketed in El Chaco showed acceptable physicochemical characteristics and complied with the evaluated quality parameters. Nevertheless, continuous monitoring, improved hygienic practices, and responsible antimicrobial management are necessary to strengthen milk safety and quality in rural dairy production systems.