Persistent organic pollutants have particular ecotoxicological importance and they are amongst the most harmful groups of persistent pollutants. The complexity of persistent organic pollutants highlights the different sources of pollution from which they came and, depending on which, their profile could be characterized. In the first part of this review, the main characteristics of persistent organic pollutants were described, focusing on their complexity and toxic potential in relation to environmental elements. The second part of the review includes data related to the occurrence and incidence of persistent organic pollutants in different types of feed and cow’s milk, focusing on the characteristic profile of pollutants as an indicator of the sources of pollution. Moreover, a description regarding the timing and duration of the contamination of feed and milk was carried out, evaluating the distribution of pollutants within the analyzed samples and highlighting those whose presence is predominant or whose residues persist in the environment for long periods. The review concludes that the identification of pollution sources associated with different proportions of organic pollutants found in different samples could represent a suitable solution for biomonitoring the potential contamination in a geographical area.