Evaluation of the systemic innate immune response and metabolic alterations of nonlactating cows with diet-induced subacute ruminal acidosis

Abstract

Subacute ruminal acidosis (SARA) increases lipopolysaccharide endotoxin in the rumen, which might translocate into the systemic circulation, triggering a cascade of clinical and immunological alterations. The objective of this study was to characterize the clinical immune and metabolic responses to ruminal-derived lipopolysaccharide in nonlactating cows induced with SARA using 2 challenges, a grain-based SARA challenge (GBSC) or an alfalfa-pellet SARA challenge (APSC). Six dry, nonlactating Holstein cows were used in a 3 × 3 Latin square arrangement of treatments with 4-wk experimental cycles. All cows received the control diet containing 70% forage and 30% mixed concentrates (dry matter basis) for 3 wk. In wk 4, cows received a control diet, GBSC (38% wheat-barley pellets, 32% other mixed concentrate, and 30% forages), or APSC (45% mixed concentrate, 32% alfalfa pellets, and 23% other forages). Total plasma proteins and immunology-related proteins, acute phase proteins, blood cells, serum chemistry, mRNA gene expression of peripheral blood cell surface markers, and selected proinflammatory cytokines were evaluated. Ruminal pH was lower in both groups with induced SARA compared with a control group. Ruminal endotoxins were higher in GBSC; however, plasma endotoxin was not detected in any study group. No significant differences in feed intake, rectal temperature, white blood cell counts, or differentials were found between control and SARA challenge groups; changes in glucose, urea, Ca, and Mg were observed in SARA groups. Total plasma proteins were lower in both SARA groups, and acute phase proteins were higher in GBSC. The expression of CD14, MD2, and TLR4 mRNA in peripheral blood leukocytes was not affected by SARA induction. The induction of SARA as a result of GBSC or APSC challenge was successful; however, LPS was not detected in plasma. Changes in clinical, metabolic, and inflammatory responses were not observed in the SARA-challenged cows, suggesting that, in this study, SARA was not associated with a systemic response to inflammation.

Impacts of Time-Fed Concentrate-Based Diets on Plasma Metabolites, Rumen Histology, and mRNA Expression of Hepatic Enzymes of Wethers

“…Animals 2020, 10, x FOR PEER REVIEW 9 of 14 and the downregulation of HMGCR expression in the liver suggest that cholesterol synthesis was being regulated during an acute response to ruminal acidosis and that the regulation of cholesterol synthesis began in the liver. Previous experiments have demonstrated that plasma glucose concentrations increase by as much as 6% during ruminal acidosis caused by increased concentrate feeding [36]. In the current study, glucose concentrations were 39% and 41% greater (p < 0.01) in wethers sampled from P2 and P3, respectively, when compared to the wethers sampled during the P1 (Table 5).…”

Dynamic role of single‐celled fungi in ruminal microbial ecology and activities

“…Therefore, it is the closest and most accurate indicator of rumen health or disorders such as SARA, because it provides direct information about the conditions within the rumen (Enemark ). Rumen pH <6 for a prolonged period for several hours a day can adversely leads to acidosis, (Rodríguez‐Lecompte et al ). Recently, Zhao et al () indicated that SARA produces a high concentration of ruminal LPS, which over activates the inflammatory pathways and significantly increases the expression and synthesis of pro‐inflammatory cytokines in the rumen epithelium, thus causing partial inflammation of the rumen.…”

“…Recently, Zhao et al () indicated that SARA produces a high concentration of ruminal lipopolysaccharides (LPS), which over‐activates the inflammatory pathways and significantly increases the expression and synthesis of proinflammatory cytokines in the rumen epithelium, thus causing partial inflammation of the rumen. Low rumen pH ranging from 5–6 for prolonged periods can negatively affect feed intake, microbial metabolism, and nutrient degradation, erratic appetite, body weight loss, ruminal motility, stasis, hyperkeratosis, and leads to acidosis, inflammation, laminitis, diarrhoea and villi wear out and bloat (Rodríguez‐Lecompte et al ). One of the consequences of a low rumen pH is the reduction/elimination of protozoa, the most effective mycotoxin degraders among the rumen microbial community.…”

Signals for identifying cows at risk of subacute ruminal acidosis in dairy veterinary practice

“…Another cause could also be local inflammation or damage to the ruminal epithelium, as commonly reported as a pathological finding in SARA (Kleen et al., ). The activation of an APR during SARA does not usually affect other clinically detectable inflammatory signs, such as increased rectal temperature, plasma fibrinogen, white blood cell count and differentials (Gozho et al., ; Li et al., Rodríguez‐Lecompte et al., ) and also total plasma proteins, globulins, fibrinogen and albumin concentrations typically remain within reference values of healthy cows (Rodríguez‐Lecompte et al., ). Acute‐phase proteins could provide realisable biomarkers of SARA.…”