66 Whole-Body Biogeography of the Bacterial Microbiota in Newborn Calves and Response of These Communities to Prenatal Vitamin and Mineral Supplementation
Authors: Luecke Sarah , Holman Devin B , Schmidt Kaycie N , James-Gzyl Katherine , Hurlbert Jennifer L , Menezes Ana Clara B , Bochantin Kerri A , Kirsch James D , Baumgaertner Friederike , Sedivec Kevin K , Swanson Kendall C , Dahlen Carl R , Amat Samat 
Published: October 2023

Abstract
During gestation, alterations in maternal nutrition during fetal development may alter growth trajectory and metabolic function in the developing fetus. Additionally, there is increasing evidence that the fetal microbiome also influences developmental outcomes. Research in this area is limited, and gastrointestinal microbiota has been the primary focus in cattle. Our objective was to assess the whole-body biogeography of the newborn calf microbiota and the response of these microbial communities and the calf immune system to prenatal vitamin and mineral (VTM) supplementation. Samples were collected from the hoof, liver, lung, nasal cavity, eye, rumen (tissue and fluid), and vagina of female beef calves that were born from dams that received either prenatal VTM or no VTM (Control; n = 7/group) throughout gestation. Calves were separated from their dams immediately after birth and fed colostrum replacement until euthanasia at 30 h post-initial colostrum feeding. The microbiota from swab and tissue samples were assessed using 16S rRNA gene sequencing (V4) and qPCR. Serum samples were processed for multiplex quantification of 15 cytokines and chemokines. Sequencing revealed the presence of a relatively diverse and complex microbiota in each of the 7 anatomical locations. The community structure of the hoof, liver, ocular, and vaginal microbiota were significantly different from the ruminal microbiota (0.64 ≥ R2 ≥ 0.12, P ≤ 0.003). The respiratory (nasal and lung) had similar community structures to that of ocular, vaginal, and ruminal fluid microbiota (P &gt; 0.11). The ocular, hoof, and vagina had the greatest microbial richness (observed ASVs; P &lt; 0.05) but similar diversity (Shannon; P &gt; 0.05) compared with other samples. The liver and ruminal fluid had the least microbially rich communities, the latter also being the least diverse (P &lt; 0.05). Firmicutes, Actinobacteriota, and Proteobacteria were the dominant phyla across all sample types, but their abundance varied by location. The ruminal fluid and hoof had the greatest bacterial concentration, while the liver, lung and ruminal tissue had reduced bacterial abundance as estimated by qPCR. An influence of VTM supplementation on microbial community structure was only detected in the ruminal fluid microbiota (P &lt; 0.01). While prenatal VTM supplementation did not affect the nasal, lung, liver, and hoof microbiota, differences (P &lt; 0.05) were detected in microbial richness (vagina), diversity (ruminal tissue and fluid, ocular), composition at the phylum level (ruminal tissue, ocular, and vagina), and total bacterial abundance (ocular and vagina). Among the 15 cytokines evaluated, the concentration of IP-10 was increased (P = 0.02) while IL-4 and IL-17A were reduced (P &lt; 0.05)