Quantitative qPCR Analysis of Ruminal Microorganisms in Beef Cattle Grazing in Pastures in the Rainy Season and Supplemented with Different Protein Levels

We tested the hypothesis that supplementation with three protein levels improves fermentation parameters without changing the rumen microbial population of grazing beef cattle in the rainy season. Four rumen-cannulated Nellore bulls (432 ± 21 kg of body weight) were used in a 4 × 4 Latin square design with four supplements and four experimental periods of 21 days each. The treatments were mineral supplement (ad libitum) and supplements with low, medium (MPS), and high protein supplement (HPS), supplying 106, 408, and 601 g/day of CP, respectively. The abundance of each target taxon was calculated as a fraction of the total 16S rRNA gene copies in the samples, using taxon-specific and domain bacteria primers. Supplemented animals showed lower ( P