Effects of subacute ruminal acidosis challenges on fermentation and endotoxins in the rumen and hindgut of dairy cows

Abstract

The effects of a grain-based subacute ruminal acidosis (SARA) challenge (GBSC) and an alfalfa-pellet SARA challenge (APSC) on fermentation and endotoxins in the rumen and in the cecum, as well as on endotoxins in peripheral blood, were determined. Six nonlactating Holstein cows with cannulas in the rumen and cecum were used in the study. A 3×3 Latin square arrangement of treatments with 4-wk experimental periods was adopted. During the first 3 wk of each experimental period, all cows received a diet containing 70% forages [dry matter (DM) basis]. In wk 4 of each period, cows received 1 of the following 3 diets: the 70% forage diet fed during wk 1 to 3 (control), a diet in which 34% of the dietary DM was replaced with grain pellets made of 50% ground wheat and 50% ground barely (GBSC), or a diet in which 37% of dietary DM was replaced with pellets of ground alfalfa (APSC). Rumen pH was monitored continuously using indwelling pH probes, and rumen fluid, blood, cecal digesta, and fecal grab samples were collected immediately before feed delivery at 0900 h and at 6 h after feed delivery on d 3 and 5 of wk 4. The time for which rumen pH was below 5.6 was 56.4, 225.2, and 298.8 min/d for the control, APSC, and GBSC treatments, respectively. Compared with the control, SARA challenges resulted in similar reductions in cecal digesta pH, which were 7.07, 6.86, and 6.79 for the control, APSC, and GBSC treatments, respectively. Compared with the control, only GBSC increased starch content in cecal digesta, which averaged 2.8, 2.6, and 7.4% of DM for the control, APSC, and GBSC, respectively. Free lipopolysaccharide endotoxin (LPS) concentration in rumen fluid increased from 10,405 endotoxin units (EU)/mL in the control treatment to 30,715 and 168,391 EU/mL in APSC and GBSC, respectively. Additionally, GBSC increased the LPS concentration from 16,508 to 118,522 EU/g in wet cecal digesta, and from 12,832 to 93,154 EU/g in wet feces. The APSC treatment did not affect LPS concentrations in cecal digesta and feces. All concentrations of LPS in blood plasma were below the detection limit of >0.05 EU/mL of the technique used. Despite the absence of LPS in blood, only GBSC increased the concentration of LPS-binding protein in blood plasma, which averaged, 8.9, 9.5, and 12.1mg/L for the control, APSC, and GBSC treatments, respectively. This suggests that GBSC caused translocation of LPS from the digestive tract but that LPS was detoxified before entering the peripheral blood circulation. The higher LPS concentration in cecal digesta in the GBSC compared with the APSC suggests a higher risk of LPS translocation in the large intestine in GBSC than in APSC.

Butyrate-Mediated Genomic Changes Involved in Non-Specific Host Defenses, Matrix Remodeling and the Immune Response in the Rumen Epithelium of Cows Afflicted With Subacute Ruminal Acidosis

“…Although the grain level in our study was not as high as that previously reported, the 45% NFC is sufficient to promote the growth of gram negative bacteria, which is correlated with the levels of rumen LPS (Zebeli and Ametaj, 2009). Although the LPS levels in this study are in relative agreement with those published earlier (Khafipour et al, 2009a;Li et al, 2012), it is not clear whether they are in sufficient concentration to favour transmigration and to trigger an immune response. In order for such a response to exist, free LPS must be transported to effector cells of the immune system by the soluble acute phase protein, LBP (Muta and Takeshige, 2001).…”

Adaptation to High Grain Diets Proceeds Through Minimal Immune System Stimulation and Differences in Extracellular Matrix Protein Expression in A Model of Subacute Ruminal Acidosis in Non-lactating Dairy Cows

“…In our model, microscopic images revealed that the extent of damage to the rumen following a HG challenge was limited to epithelial sloughing and to a lesser extent tight junction degradation (Steele et al 2011a); this sloughing was restored with an epithelium that was adapted to accommodate the HG challenge. Since the rumen epithelium became slightly permeable, it is possible that some microorganisms penetrated to the submucosal layers, since elevated levels of Lipopolysaccharide Binding Protein (LPSBP) were detected using the same model in subsequent experiments (Li et al, 2012;Steele et al, 2012). Because of the limited extent of pathogenic organisms and LPS infiltration, the inflammatory phase of the wound healing cascade was extremely limited.…”

Effects of duration of moderate increases in grain feeding on endotoxins in the digestive tract and acute phase proteins in peripheral blood of yearling calves

“…The increase in acute phase proteins, also referred to as an acute phase response, could be caused by the translocation of LPS from the digestive tract into the peripheral circulation (Emmanuel et al, 2008;Plaizier et al, 2012). Gozho et al (2007), Emmanuel et al (2008), Khafipour et al (2009b), and Li et al (2012b) reported that increased grain feeding increased the concentration of LPS in rumen and cecal digesta, and the concentration of acute phase proteins in peripheral blood. Increasing grain inclusion to induce SARA in dairy cows results in major changes in the microbiota of rumen digesta, including increases in starch-and soluble sugar-fermenting bacteria, lactic acid-fermenting bacteria, and Escherichia coli, as well as a reduction in the population of gram-negative Bacteroidetes (Nagaraja and Titgemeyer, 2007;Khafipour et al, 2009c).…”

“…These energy-dense diets are primarily obtained with moderate to high inclusion rates of grain. However, these types of diets can affect cattle health, as increases in grain feeding have been associated with a heightened risk for SARA, increased concentrations of endotoxic LPS in the gut, as well as increased concentrations of acute phase proteins in peripheral blood (Gozho et al, 2007;Emmanuel et al, 2008;Li et al, 2012b).…”