Effects of a blend of essential oils in milk replacer on performance, rumen fermentation, blood parameters and health scores of dairy heifers

Joana P. Campolina; Sandra G. Coelho; Anna Luiza Belli; Fernanda S. Machado; Luiz G. R. Pereira; Thierry R. Tomich; Wanessa A. Carvalho; Rodrigo O. S. Silva; Alessandra L. Voorsluys; David V. Jacob; Mariana M. Campos

It has been reported that essential oils have an antiseptic and antimicrobial activity 567 that may be beneficial in balancing intestinal microbiota (43). Gram positive bacteria 568 are the most sensitive to the essential oils microbial activity (7,12), but it is possible that 569 gram negative bacteria and some types of parasites are also susceptible (9) to different 570 essential oils. Thus, essential oils could reduce the incidence and severity of diarrhea 571 syndrome in calves trough inhibition of coliform overgrowth (44). BEO in 1.0 µg/mL 572 concentration did not inhibit bacterial growth -both E. coli and S. tryphimurium. Thus, . CC-BY 4.0 International license author/funder. It is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/2020.03.17.995209 doi: bioRxiv preprint 28 573 at this concentration BEO did not have any antibacterial in vitro effect. However, 574 besides no direct influence found over the bacterial evaluation, BEO calves presented 575 differences on basophil (Table 6 ) and lymphocyte cell populations (Fig 2) which could 576 be associated to modulation of inflammatory immune response. Thus, outcomes found 577 on fecal and respiratory scores could be associated to indirect changes in hemato-578 biochemical parameters since essential oils have antioxidant and anti-inflammatory 579 effect. Feeding BEO to pre-weaned heifers on MR did not affect intake, performance 583 parameters, blood metabolites or IGF-1 concentration. However, it changed C2:C3 584 proportion during pre-and post-weaning periods, as well as showed signs of immunity 585 improvement and lower fecal scores in the pre-weaning phase. Further research is 586 needed to define the best rout and dosage as well as understand the essential oils 587 contribution on decrease morbidity of neonatal diseases. Therefore, essential oils are a 588 health additive option to modern production sytems, and could be used as an alternative 589 to improve calf health and performance.