Effects of an intramammary LPS challenge in lactating Holstein cows fed a probiotic-postbiotic blend on performance, inflammation, and paracellular permeability of the gastrointestinal tract

This study evaluated the effects of feeding a probiotic-postbiotic blend on DMI, milk and milk component yields, systemic inflammation, and regional paracellular permeability of the gastrointestinal tract (GIT) before and after exposure to an intramammary (IMM) challenge of LPS or no infusion. Lactating Holstein cows (n = 34 at 57 ± 4 DIM) with a SCC <250,000 cells/mL were used, including 14 that were ruminally cannulated. Cows were fed either 28 g/d of a probiotic-postbiotic blend (PB; Dairyman's Edge PRO, Papillon Agricultural Company) or no PB (NP) for 21 d before obtaining 5 d of baseline measurements. On d 27, cows received a mammary treatment (MTrt) of either 200 µg of Escherichia coli O111:B4 LPS (IML) using sterile PBS as a carrier into both rear quarters or no infusion (CON; PB-IML, n = 8; PB-CON, n = 9; NP-IML, n = 8; NP-CON, n = 9). Milk and milk component yields and DMI were not affected by PB before the MTrt. The IML increased rectal temperature by 2.8°C 6 h after the MTrt application and tended to be 0.3°C lower for PB than NP at 12 h. Milk SCS was 11 units greater at 12 h for IML versus CON and remained 1 unit greater on d 12. Relative to CON, IML reduced DMI by 28%, 11%, and 10%, and milk yield by 44%, 22%, and 10% on d 1 to 3 after the MTrt application, respectively. Dry matter intake recovered after d 4, whereas milk yield was not different on d 5 and 6 but was 6% lower for IML than CON on d 7 and 8. Milk fat yield was reduced for IML from d 1 to 13 when compared with CON. The PB reduced ruminal pH by 0.11 units, increased total short-chain fatty acid concentrations by 6% compared with NP, and stabilized the proportions of propionate and acetate following MTrt application. Plasma haptoglobin (Hp) and serum amyloid A (SAA) were greatest on d 2 for IML (562- and 16-fold greater than CON, respectively). On d 7 and 12, Hp was 37- and 6-fold greater for IML versus CON, respectively. Serum amyloid A was reduced by 42% for PB versus NP. On d 1 after the MTrt application, plasma Cr and Co area under the curve (AUC) were 24% and 28% lower for IML than CON, respectively. On d 6, Co AUC was 33% lower for IML than CON but the Cr AUC did not differ on d 6 or 11, and Co AUC did not differ on d 11. In conclusion, the IML infusion induced local and systemic inflammation resulting in reduced milk and milk fat yields that persisted beyond the decline in DMI. The PB did not improve recovery of DMI or milk yield but altered ruminal fermentation, reduced SAA, and tended to accelerate recovery of normothermia. Total GIT and postruminal paracellular permeability may transiently decrease in response to mammary and systemic inflammation, at least based on the Cr and Co AUC in plasma. These findings highlight the limited understanding whereby inflammation in the mammary gland, and potentially other non-GIT organs, influence paracellular permeability of the GIT in ruminants.

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