Abstract
Subacute ruminal acidosis (SARA) is a metabolic disorder in dairy cows that is associated with dysbiosis of rumen and hindgut microbiomes, translocation of immunogenic compounds from the gut lumen into blood circulation, and systemic inflammatory response. In this study we hypothesized that Saccharomyces cerevisiae fermentation products (SCFP) attenuate the increases in ruminal and peripheral bacterial endotoxin concentrations and the inflammation resulting from repeated induction of SARA. Lactating Holstein dairy cows (parity 2 and 3+, n = 32) were fed diets with or without SCFP (all from Diamond V) and subjected to 2 episodes of SARA challenges. Cows received a basal total mixed ration (TMR) containing 34% neutral detergent fiber and 18.6% starch, dry matter (DM) basis. Treatments were randomly assigned to control (basal TMR and 140 g/d of ground corn with no SCFP) or 1 of 3 SCFP treatments: basal TMR and 14 g/d Original XPC (SCFPa), 19 g/d NutriTek (SCFPb-1×), or 38 g/d NutriTek (SCFPb-2×) mixed with 126, 121, or 102 g/d of ground corn, respectively. Treatments were implemented from 4 wk before until 12 wk after parturition. During wk 5 (SARA1) and wk 8 of lactation (SARA2), grain-based SARA challenges were conducted by gradually replacing 20% of DM of the basal TMR over 3 d with pellets containing 50% wheat and 50% barley. Ruminal fluid, fecal, and blood samples were collected weekly during Pre-SARA1 (wk 4, as baseline), Post-SARA1 (wk 7), and Post-SARA2 (wk 10 for blood and wk 12 for rumen and fecal parameters) stages, and twice a week during the challenges SARA1 and SARA2. Rumen papillae samples were taken only during Pre-SARA1 and Post-SARA2. We measured the concentrations of free lipopolysaccharides (LPS) in the rumen fluid and feces; free LPS and lipoteichoic acid (LTA) endotoxins in peripheral plasma; interleukin (IL)-1β and IL-6 in peripheral serum; acute-phase proteins, serum amyloid A (SAA), and LPS-binding protein in peripheral plasma; haptoglobin (Hp) in peripheral serum; and myeloperoxidase (MPO) in rumen papillae. Induction of SARA episodes increased free LPS concentrations in rumen fluid and tended to increase LTA in peripheral plasma. The SARA episodes increased concentration of circulating SAA and tended to increase that of IL-1β compared with Pre-SARA1. Induction of SARA did not affect the concentrations of circulating IL-6, Hp, and MPO. The SCFP supplementation reduced plasma concentrations of LTA and SAA and serum concentration of IL-1β compared with control. Additionally, SCFPb-2× tended to reduce ruminal LPS in second-parity cows compared with control. Overall, SCFP supplementation appeared to stabilize the rumen environment and reduce proinflammatory status, hence attenuating adverse digestive and inflammatory responses associated with SARA episodes.
Highlights
A postbiotic is a “preparation of inanimate microorganisms and/or their components that confers a health benefit on the host” (Salminen et al, 2021)
One cow in the SCFPb-2× group was diagnosed with milk fever during the transition period; she recovered before SARA1 was conducted
SARA challenges increased blood plasma concentrations of serum amyloid A (SAA) and tended to increase that of IL-1β compared with Pre-SARA1, without affecting the plasma concentration of Hp and serum concentration of IL-6 (Table 4; Supplemental Tables S3, S6, and S7, https://figshare.com/articles/online_resource/Supplemental_data_for_DOI_10_3168_jds_2021-20572/17162603, Guo et al, 2021)
Summary
A postbiotic is a “preparation of inanimate microorganisms and/or their components that confers a health benefit on the host” (Salminen et al, 2021). Beneficial health effects of SCFP supplementation during SARA have been suggested (Li et al, 2016) This common metabolic disorder causes substantial economic loss to dairy farms and reduces the health and welfare of dairy cows (Krause and Oetzel, 2006; Plaizier et al, 2012); SARA has been associated with systemic inflammation (Krause and Oetzel, 2006) and dysbiosis of the rumen (Tun et al, 2020) and hindgut microbiota at the luminal, epimural, and mucosaassociated levels (Plaizier et al, 2021). Strategies that help stabilize conditions across the gastrointestinal tract, attenuate endotoxin release during SARA, prime the functionality of immune cells, and strengthen immune response may mitigate the adverse effects of SARA on health and production of lactating dairy cows
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