Potential benefits of a blend of essential oils on metabolism, digestibility, organ development and gene expression of dairy calves.

The objective of this study was to evaluate blood cells and metabolites, insulin-like growth factor-1 (IGF-1), digestibility, internal organs weight and histology, gene expression, and spleen cell proliferation of pre-weaned bull calves supplemented with a blend of essential oils in milk replacer (MR). Sixteen newborn Holstein × Gyr crossbred dairy bull calves, with body weight at birth of 33.3 ± 3.7 kg, were housed in individual sand bedded pens, blocked by genetic composition, and randomly assigned to 1 of 2 treatments in a randomized complete block design: Control (CON, n = 8) and blend of essential oils supplementation (BEO, n = 8, 1 g/day/calf, Apex Calf, Adisseo, China). The commercial blend was composed by plant extracts derived from anise, cinnamon, garlic, rosemary, and thyme. Animals were fed 5 L of MR/day reconstituted at 15% (dry matter basis), divided into two equal meals. Water and starter were provided ad libitum. ß-hydroxybutyrate, urea, and glucose were evaluated weekly, IGF-1 was evaluated biweekly, and total blood cell count was performed every four weeks until the end of the trial at eight weeks of age. Feed samples were collected three times a week and polled for weekly analysis. Apparent total nutrient digestibility was determined from d 56 to 60 of age. On d 60 ± 1, animals were euthanized for organ weight, histology, spleen cell proliferation, and intestinal gene expression analysis. Data were analyzed independently using linear mixed models using the REML method in the nlme package in R for continuous outcomes. A non-parametric test was used for ordered categorical outcomes using the Artools package in R. There were no differences between groups for blood evaluations, digestibility, gene expression, and a spleen cell proliferation assay. However, BEO calves presented a heavier pancreas, heavier intestines, bigger ileum villi, and higher cecum butyrate levels (P < 0.05), demonstrating that the EO supplementation helped intestinal development and symbiotic bacteria. It was also observed in CON animals' heavier respiratory tract and a higher eosinophil count (P < 0.05). Therefore, the organs where eosinophils are more active had a better response for BEO animals. No differences were found in the intestinal gene expression in the immune context. These results demonstrate that supplementing essential oils in MR could contribute to gut development and immune function. However, more research is needed to understand its impact on body development and define the best dosage and route of administration.

Species-level identification of staphylococci isolated from bovine mastitis in Brazil using partial 16S rRNA sequencing.

Staphylococci isolated from bovine milk and not classified as Staphylococcus aureus represent a heterogeneous group of microorganisms that are frequently associated with bovine mastitis. The identification of these microorganisms is important, although it is difficult and relatively costly. Genotypic methods add precision in the identification of Staphylococcus species. In the present study, partial 16S rRNA sequencing was used for the species identification of coagulase-positive and coagulase-negative staphylococci isolated from bovine mastitis. Two hundred and two (95%) of the 213 isolates were successfully identified at the species level. The assigning of an isolate to a particular species was based on ≥99% identity with 16S rRNA sequences deposited in GenBank. The identified isolates belonged to 13 different Staphylococcus species; Staphylococcus chromogenes, S. aureus and Staphylococcus epidermidis were the most frequently identified species. Eight isolates could not be assigned to a single species, as the obtained sequences showed 99% or 100% similarity to sequences from two or three different Staphylococcus species. The relatedness of these isolates with the other isolates and reference strains was visualized using a cladogram. In conclusion, 16S rRNA sequencing was an objective and accurate method for the proper identification of Staphylococcus species isolated from bovine mastitis. Additional target genes could be used in non-conclusive cases for the species-level identification of these microorganisms.