64 Late gestation maternal feed restriction alters specific rumen microbiota of the neonatal beef calf

Abstract Abstract: Introduction Feed restriction during late gestation in beef cattle is a relevant issue in the inter- mountain west due to the overlap of limited and low-quality feed resources with heightened energy requirements associated with late gestation and early lactation. Little is known how this period of potential restriction may impact the rumen microbiota or the neonatal calf. Objectives The objective of this research was to asses the effects of maternal feed restriction on offspring rumen microbiota. We hypothesize that there will be microbial profile differences between calves born to control fed versus feed restricted cows and that those differences persist through one month of age. Methods Mature cows (n = 30) were provided 100% of intake requirements (CON) or 70% of the intake volume (FR). Restriction began 60d prior to calving and continued through one-month post-parturition. Eight animals from each treatment were randomly selected for sampling. Rumen fluid was collected from the calf at birth (RFd1), d7 (RFd7), and d28 (RFD28) post- parturition. DNA was isolated using a lysis buffer and mechanical bead-beating procedure and purified using the QIAamp DNA Stool Mini Kit (Qiagen). Amplicon sequencing of the 16S rRNA V4 region was completed on the MiSeq and analyzed with ANCOM-BC plugin within QIIME2. Results At birth, the phylum Fibrobacterota was enriched in FR calves (q = 0.003) where Sumerlaeota was depleted (q = 0.03) compared to CON calves. Desulfobacterota was enriched in FR calves (q = 0.02) and Deferribacterota was depleted (q = 0.01) relative to CON calves at d7. At d 28, the phylum Patescibacteria was depleted (q ≤ 0.001) in FR calves compared to CON calves. Results indicate feed restriction during gestation could influence calf rumen profiles with potential impacts on functions such as degradation of cellulose, sulfur cycling, and utilization of iron. More research is needed to determine if these differences have implications in long-term animal health and performance.