Desenvolvimento da microbiota nasofaringeana em bezerros Holandês

Abstract

Understanding the dynamics of bacterial colonization of the nasopharynx in calves can provide important answers regarding the occurrence of respiratory disease in cattle and the potential for manipulating this microbiota. To the best of our knowledge, this is the first study to analyze this dynamic in Brazil. The objective of this study was to characterize the bacterial microbiota of the nasopharynx of healthy Holstein calves between 3 and 56 days of age. Nasopharyngeal swab samples were collected from six Holstein calves at 3, 7, 14, 28, 42, and 56 days of age, and sequencing of the V3/V4 regions of 16S ribosomal RNA was performed. Clinical evaluation was performed throughout the study period to account for possible health events that could interfere with the metagenomic analyses. The most abundant phyla detected were Proteobacteria (89.84%), Actinobacteria (4.93%), and Firmicutes (4.15%). The phylum Proteobacteria predominated in all samples, with dominance driven mainly by the genera Pseudomonas spp. and Stenotrophomonas spp. When grouping the collection days into Period 1 (3, 7, and 14 days) and Period 2 (28, 42, and 56 days), a significant difference was observed in the composition of the microbiota between the periods, with lower diversity in Period 2 (p<0.05). The diversity of the nasopharyngeal microbiota of calves decreases over time, and this change coincides with changes in the diet and immune status of these animals, as well as coinciding with the onset of bronchopneumonia in this species, which may be a factor that helps explain this fact. The findings of this study, especially the nasopharyngeal ecological shift that occurs around 28 days of age, help to elucidate the dynamics of initial colonization of the upper respiratory tract in cattle and may serve as a basis for prevention strategies for the occurrence of respiratory diseases in calves.