{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,20]],"date-time":"2026-10-20T15:41:16Z","timestamp":1792510876957,"version":"4.5.0"},"reference-count":52,"publisher":"American Society for Microbiology","issue":"10","license":[{"start":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T00:00:00Z","timestamp":1791244800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T00:00:00Z","timestamp":1791244800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"funder":[{"name":"Pennsylvania Center for Livestock and Poultry Excellence"}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Microbiol Spectr"],"published-print":{"date-parts":[[2026,10,6]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title\/>\n                    <jats:p>\n                      The early-life gut microbiome represents a window during which microbial alterations may impact long-term health and productivity. However, most research has focused on confined dairy systems with limited breed variation. To address this gap, we examined bacterial community dynamics in pasture-raised South Poll \u00d7 Angus and Angus cow\u2013calf pairs (\n                      <jats:italic toggle=\"yes\">n<\/jats:italic>\n                      = 7). Fecal samples were collected from calves at birth and weekly through 8 weeks, with dam\u2019s samples collected post-calving. DNA was extracted from fecal samples, and bacterial communities were profiled using the V1\u2013V2 region of the 16S rRNA gene. Alpha diversity increased significantly with age (richness\n                      <jats:italic toggle=\"yes\">\u03c1<\/jats:italic>\n                      &lt; 0.01, Shannon\n                      <jats:italic toggle=\"yes\">\u03c1<\/jats:italic>\n                      &lt; 0.01), while beta diversity exhibited strong temporal structuring (weighted\n                      <jats:italic toggle=\"yes\">R<\/jats:italic>\n                      \u00b2 = 0.33,\n                      <jats:italic toggle=\"yes\">\u03c1<\/jats:italic>\n                      = 0.001; unweighted\n                      <jats:italic toggle=\"yes\">R<\/jats:italic>\n                      \u00b2 = 0.38,\n                      <jats:italic toggle=\"yes\">\u03c1<\/jats:italic>\n                      = 0.001), as calf communities converged toward adult reference states by 8 weeks. Sex exerted modest but detectable effects on community structure. Taxonomic analyses identified a core microbiome of 25 taxa that accounted for most community structure and defined discrete temporal phases of development. Early fecal samples were dominated by\n                      <jats:italic toggle=\"yes\">Lactobacillus<\/jats:italic>\n                      ,\n                      <jats:italic toggle=\"yes\">Bacteroides<\/jats:italic>\n                      , and facultative anaerobes. These taxa declined rapidly with age, coincident with increases in\n                      <jats:italic toggle=\"yes\">Ruminococcus<\/jats:italic>\n                      ,\n                      <jats:italic toggle=\"yes\">Blautia<\/jats:italic>\n                      ,\n                      <jats:italic toggle=\"yes\">Dorea<\/jats:italic>\n                      ,\n                      <jats:italic toggle=\"yes\">Lachnospiraceae<\/jats:italic>\n                      , and\n                      <jats:italic toggle=\"yes\">Clostridiales<\/jats:italic>\n                      (\n                      <jats:italic toggle=\"yes\">q<\/jats:italic>\n                      &lt; 0.05). Calf average daily gain was positively correlated with\n                      <jats:italic toggle=\"yes\">Streptococcus<\/jats:italic>\n                      ,\n                      <jats:italic toggle=\"yes\">Dorea<\/jats:italic>\n                      , and\n                      <jats:italic toggle=\"yes\">Bacillus<\/jats:italic>\n                      and negatively correlated with\n                      <jats:italic toggle=\"yes\">Ruminococcaceae<\/jats:italic>\n                      (\n                      <jats:italic toggle=\"yes\">\u03c1<\/jats:italic>\n                      &gt; 0.3,\n                      <jats:italic toggle=\"yes\">q<\/jats:italic>\n                      &lt; 0.05). These findings demonstrate rapid gut microbiome development in pastured beef calves, similar in pace but distinct in composition from confined dairy systems, underscoring the importance of environment and breed diversity in shaping early-life microbial colonization.\n                    <\/jats:p>\n                    <jats:sec>\n                      <jats:title>IMPORTANCE<\/jats:title>\n                      <jats:p>\n                        Early-life microbial colonization plays a critical role in shaping gastrointestinal physiology and immune-cell maturation, with impacts on long-term productivity in cattle. However, most studies describing microbial succession focused on Holstein calves raised in confinement systems, leaving the microbial ecology of beef calves, particularly crossbreds and those on pasture, poorly characterized. In this study, we longitudinally characterized hindgut microbial development in Angus \u00d7 South Poll and Angus calves during the first 8 weeks of life. We demonstrate a structured microbial succession driven by a core set of taxa that evolves with age, with continuous dominance of\n                        <jats:italic toggle=\"yes\">Lactobacillus<\/jats:italic>\n                        . These findings establish foundational knowledge of microbiome assembly in a breed of beef calves growing in popularity and highlight microbial taxa and community structures that may relate to breed genetics influencing growth and health. Understanding microbial development in pasture-based beef systems provides an essential framework for designing microbiome-informed management or nutritional interventions aimed at improving productivity and sustainability, particularly in pasture-raised animals.\n                      <\/jats:p>\n                    <\/jats:sec>\n                  <\/jats:sec>","DOI":"10.1128\/spectrum.01730-26","type":"journal-article","created":{"date-parts":[[2026,8,21]],"date-time":"2026-08-21T13:03:50Z","timestamp":1787317430000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Dynamic changes in the hindgut bacterial community of pre-weaning crossbred beef calves in a pasture-based system"],"prefix":"10.1128","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-6840-9427","authenticated-orcid":false,"given":"A.","family":"Post","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/00b30xv10","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Clinical Studies, New Bolton Center, University of Pennsylvania, School of Veterinary Medicine","place":["Kennett Square, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"T.","family":"Webb","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/00b30xv10","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Clinical Studies, New Bolton Center, University of Pennsylvania, School of Veterinary Medicine","place":["Kennett Square, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9424-2155","authenticated-orcid":true,"given":"N.","family":"Indugu","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/00b30xv10","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Clinical Studies, New Bolton Center, University of Pennsylvania, School of Veterinary Medicine","place":["Kennett Square, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"B. 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