Introduction. The content of phenolic compounds in fodder plants is positively associated with low parasite loads in cattle (Provenza and Villalba, 2010). Various plants that contain compounds such as terpenes, alkaloids, saponins, anthraquinones and tannins have been used to control livestock parasites (Alonso-Díaz et al., 2009). Objective. This study was to associate parasite loads of cattle that consume diversified diets to secondary compounds contained in plants, in environments with high plant diversity. Methods. A study was carried out in sites classified in three grazing environments: eight monocultures of grasses (MonoGram), three biodiverse grasslands (PasBio) and four with secondary vegetation (VegSec); Feces were sampled to determine the parasite load of bovines at each site (McMaster technique), physiological status was recorded, diet composition of cattle was assessed using the bite-counting technique, and the concentration of total phenolic compounds and total tannins were determined. Only for the more abundant plants in the diet. Results and discussion. Parasite positive and negative animals were diagnosed at all sites, with parasite loads between 0 and 4 600 hpg; cattle included different number of plant species in their diets depending on the site: 1-7 in Mongram, 9-14 in PasBio and 16-36 in VegSec; All the plants collected (the most abundant in the diet) contained phenolic compounds and tannins, although in different amounts, ranging from 0.99% to 28.09% phenols and from 0.46% to 26.41% tannins. Conclusions. Preliminary results indicate that the ingestion of plants containing phenolic compounds and tannins affect parasite loads of cattle, and this is related to the physiological status.