Seven multiparous Holstein cows with a ruminal fistula were used to investigate the changes in rumen microbiota, gene expression of the ruminal epithelium, and blood biomarkers of metabolism and inflammation during the transition period. Samples of ruminal digesta, biopsies of ruminal epithelium, and blood were obtained during -14 through 28d in milk (DIM). A total of 35 genes associated with metabolism, transport, inflammation, and signaling were evaluated by quantitative reverse transcription-PCR. Among metabolic-related genes, expression of HMGCS2 increased gradually from -14 to a peak at 28 DIM, underscoring its central role in epithelial ketogenesis. The decrease of glucose and the increase of nonesterified fatty acids and β-hydroxybutyrate in the blood after calving confirmed the state of negative energy balance. Similarly, increases in bilirubin and decreases in albumin concentrations after calving were indicative of alterations in liver function and inflammation. Despite those systemic signs, lower postpartal expression of TLR2, TLR4, CD45, and NFKB1 indicated the absence of inflammation within the epithelium. Alternatively, these could reflect an adaptation to react against inducers of the immune system arising in the rumen (e.g., bacterial endotoxins). The downregulation of RXRA, INSR, and RPS6KB1 between -14 and 10 DIM indicated a possible increase in insulin resistance. However, the upregulation of IRS1 during the same time frame could serve to restore sensitivity to insulin of the epithelium as a way to preserve its proliferative capacity. The upregulation of TGFB1 from -14 and 10 DIM coupled with upregulation of both EGFR and EREG from 10 to 28 DIM indicated the existence of 2 waves of epithelial proliferation. However, the downregulation of TGFBR1 from -14 through 28 DIM indicated some degree of cell proliferation arrest. The downregulation of OCLN and TJP1 from -14 to 10 DIM indicated a loss of tight-junction integrity. The gradual upregulation of membrane transporters MCT1 and UTB to peak levels at 28 DIM reflected the higher intake and fermentability of the lactation diet. In addition, those changes in the diet after calving resulted in an increase of butyrate and a decrease of ruminal pH and acetate, which partly explain the increase of Anaerovibrio lipolytica, Prevotella bryantii, and Megasphaera elsdenii and the decrease of fibrolytic bacteria (Fibrobacter succinogenes, Butyrivibrio proteoclasticus). Overall, these multitier changes revealed important features associated with the transition into lactation. Alterations in ruminal epithelium gene expression could be driven by nutrient intake-induced changes in microbes; microbial metabolism; and the systemic metabolic, hormonal, and immune changes. Understanding causes and mechanisms driving the interaction among ruminal bacteria and host immunometabolic responses merits further study.

The study investigated the effect of an intramammary lipopolysaccharide (LPS) challenge on the bovine mammary and liver transcriptome and its consequences on metabolic biomarkers and liver tissue composition. At 7 days of lactation, 7 cows served as controls (CTR) and 7 cows (LPS) received an intramammary Escherichia coli LPS challenge. The mammary and liver tissues for transcriptomic profiling were biopsied at 2.5 h from challenge. Liver composition was evaluated at 2.5 h and 7 days after challenge, and blood biomarkers were analyzed at 2, 3, 7 and 14 days from challenge. In mammary tissue, the LPS challenge resulted in 189 differentially expressed genes (DEG), with 20 down-regulated and 169 up-regulated. In liver tissue, there were 107 DEG in LPS compared with CTR with 42 down-regulated and 65 up-regulated. In mammary, bioinformatics analysis highlighted that LPS led to activation of NOD-like receptor signaling, Toll-like receptor signaling, RIG-I-like receptor signaling and apoptosis pathways. In liver, LPS resulted in an overall inhibition of fatty acid elongation in mitochondria and activation of the p53 signaling pathway. The LPS challenge induced changes in liver lipid composition, a systemic inflammation (rise of blood ceruloplasmin and bilirubin), and an increase in body fat mobilization. The data suggest that cells within the inflamed mammary gland respond by activating mechanisms of pathogen recognition. However, in the liver the response likely depends on mediators originating from the udder that affect liver functionality and specifically fatty acid metabolism (β-oxidation, ketogenesis, and lipoprotein synthesis).

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Finishing cattle are exposed to diets with high amounts of starch and consequently to hindgut acidosis. Usually, antibiotics like ionophores are used to control dysbiosis at gut level. However, natural options are being evaluated as healthy alternatives. Flavonoids are well known as antibacterial agent, being an interesting alternative to antibiotics. The aim of this experiment was to evaluate the performance of finishing steers supplemented with monensin compared with citrus flavonoid extract (Bioflavex). Steers (n = 48; 214.3 kg live weight; LW) were assigned to two treatments: Monensin (MON; 30 g/tn DM) and flavonoids extract (FLAV; Bioflavex, Spain; 400 g/tn DM). Animals were allocated in 6 groups (3 pens/treatment; 8 animals/pen). Pen was considered as the experimental unit. Transition diet was offered from d 1 to 21 (CP 18% , starch 40.6%) whilst finishing diet from d 21 to 86; (CP 10.6%, starch 47.8%). The LW was registered at 0, 21 and 86 d. The DMI was estimated by difference between offered and refusals. Ruminal and feces pH were recorded (rumen liquor samples were obtained by ruminocentesis). Data were analyzed by proc mixed (treatment and time as fixed effects; pen as random). Differences were stated when P< 0.05. Only DMI was different between treatments, being FLAV greater than MON (6.68 kg/d vs 6.45 kg/d for FLAV and MON respectively; P< 0.05). No differences were found in terms of daily gain (1.355 kg/d vs 1.294 kg/d for FLAV and MON respectively; P >0.05), final weight (FLAV 331.6 kg vs MON 324.8 kg; P >0.05), neither conversion (4.95 kg/kg vs 4.98 kg/kg for FLAV and MON respectively; P >0.05). Rumen and feces pH did not differ across treatments (P >0.05). According to our results, a citrus flavonoid extract showed a similar performance comparing to monensin, being a potential alternative to antibiotics.