Identification and Quantification of Rumen Ciliated Protozoa From Crossbred Beef Cattle Fed Winter or Summer Grasses Preslaughter

The aim was to identify, quantify, and correlate ciliated protozoa from the rumen of crossbred beef cattle (European × Nellore) fed winter (ryegrass or ryegrass + white oats) or summer ( Brachiaria spp. or Brachiaria spp. + stargrass) pastures in the preslaughter period. Ruminal content samples were obtained from the center of the rumen mass after animal slaughter. Quantification and identification of ciliated protozoa genera were performed using a Sedgewick–Rafter chamber under optical microscopy. The experimental design was completely randomized, with four treatments and ten replicates. A descriptive analysis was performed to obtain dispersion measures, and a multivariate principal component technique was applied. Only protozoa populations showing a correlation greater than 50% ( p < 0.05) with one of the first two main components were considered for grouping. Nine genera of ciliated protozoa were highly prevalent, with Diplodinium being the predominant genus. A higher concentration of ciliated protozoa was observed in the rumen of animals finished on summer pastures, primarily the mixed Brachiaria spp. + stargrass pasture. The concentration of ciliated protozoa was greater in animals finished on summer pastures, likely due to the increased activity of these protozoa, which intensively degrade structural carbohydrates, including cellulose and hemicellulose.