This paper reports the first immunoplatforms for the detection of adulteration in milk with milk or colostrum from other animals. The developed electrochemical bioplatforms allow the reliable determination of immunoglobulins G (IgGs) from cows, sheeps, or goats. They rely on sandwiching each animal species-specific IgGs with selective antibody pairs [unconjugated and conjugated with horseradish peroxidase (HRP)] onto magnetic microbeads (MBs) used as solid supports and amperometric transduction with the H2O2/hydroquinone (HQ) system at disposable electrodes. The immunoplatforms allow achieving limits of detection (LODs) of 0.74, 0.82, and 0.66 ng mL-1 for bovine, ovine, and caprine IgGs, respectively, which are lower than those obtained with conventional enzyme-linked immunosorbent assay (ELISA) methodologies and in 2-5 times shorter time. The bioplatforms were successfully applied to the determination of the individual content of the target IgGs in milk samples of different animals (cow, sheep, and goat) and type (colostrum, raw, and pasteurized), without matrix effect and after just a sample dilution. They were also applied to the detection of adulteration with milks from other animals at levels below than those required by the European legislation (1.0%, v/v). The possibility to detect milk adulteration with colostrum using a strategy based on the measurement of the total content of the three target IgGs in raw milks is also demonstrated. Multiplexing platforms were constructed to be used in routine surveillance of milk. They are able to provide in a single run and in just 30 min relevant information regarding the milk sample including its animal origin, the undergone heat treatment, and whether it was adulterated with milk or colostrum from other species.