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ARS Home » Midwest Area » Lexington, Kentucky » Forage-animal Production Research » Research » Publications at this Location » Publication #314461

Title: Exogenous lactobacilli mitigate microbial changes associated with grain fermentation in vitro

item HARLOW, BRITTANY - University Of Kentucky
item LAWRENCE, LAURIE - University Of Kentucky
item Kagan, Isabelle
item HARRIS, PATRICK - Buckeye Technologies
item Flythe, Michael

Submitted to: Proceedings of the Equine Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 4/25/2015
Publication Date: 5/26/2015
Citation: Harlow, B.E., Lawrence, L.M., Kagan, I., Harris, P., Flythe, M.D. 2015. Exogenous lactobacilli mitigate microbial changes associated with grain fermentation in vitro. Proceedings of the Equine Science Society. 35:400-417.

Interpretive Summary:

Technical Abstract: Cereal grains are often included in equine diets. Sugars and starch in grains can be digested and absorbed in the small intestine, but a high proportion of grain in the diet can allow starch to reach the hindgut, disturbing the microbial ecology. Streptococci and lactobacilli both catabolize starch and produce lactic acid, which can decrease hindgut pH leading to detrimental health effects (e. g. hindgut acidosis). Probiotics are reported to mitigate GI dysbioses, and bacteria in Genus Lactobacillus are commonly used. This study was conducted to determine the effect of different starch sources and exogenous lactobacilli on pH as well as the growth of starch-utilizing (SU) bacteria (including streptococci and lactobacilli) and lactate-utilizing (LU) bacteria. Feces were collected on different days from 3 mature Thoroughbred geldings fed grass hay with access to pasture. Fecal microbes were harvested by differential centrifugation, washed, and re-suspended in anaerobic media containing finely ground corn, steam flaked corn (SFC), wheat, or oats at 1.6% (w/v) starch concentration and one of the following treatments: 1) Control (substrate only), 2) L. acidophilus, 3) L. buchneri, 4) L. reuteri, or 5) an equal mixture of all three (Mix; 107 final concentration). After 24 h of incubation (37 ºC, 160 rpm) samples were collected for pH and enumerations of GDGPC (Enterococci, Streptococcus bovis/equinus), lactobacilli, SU bacteria, and LU bacteria. Enumeration data were log transformed prior to ANOVA using SAS (v. 9.3). Extent and mitigation of acidification depended on grain type and lactobacilli addition. Lactobacilli increased pH compared to control, in corn, SFC, and wheat fermentations (P < 0.0001, in all cases). Specifically, addition of either L. reuteri or L. acidophilus was most effective at mitigating pH decline with both corn and wheat fermentation, in which the greatest acidification occurred (P <0.05, in all cases). Addition of lactobacilli decreased SU in corn and wheat fermentations while increasing LU in corn, SFC, and wheat fermentations (P < 0.0001, in all cases). In oat fermentations, L. acidophilus and L. reuteri increased pH and LU while decreasing SU-bacteria (P < 0.0001, in all cases). In all substrates, L. reuteri -treated suspensions had the lowest number of GDGPC and the highest number of lactobacilli and LU bacteria (P < 0.05, in all cases). These results indicate that exogenous lactobacilli can impact the microbial community composition and pH of cereal grain fermentations by equine hindgut microorganisms in vitro.