Exogenous lactobacilli mitigate microbial changes associated with grain fermentation (corn, oats, and wheat) by equine fecal microflora ex vivo.
Abstract: Cereal grains are often included in equine diets. When starch intake exceeds foregut digestion starch will reach the hindgut, impacting microbial ecology. Probiotics (e.g., lactobacilli) are reported to mitigate GI dysbioses in other species. This study was conducted to determine the effect of exogenous lactobacilli on pH and the growth of amylolytic and lactate-utilizing bacteria. Feces were collected from 3 mature geldings fed grass hay with access to pasture. Fecal microbes were harvested by differential centrifugation, washed, and re-suspended in anaerobic media containing ground corn, wheat, or oats at 1.6% (w/v) starch and one of five treatments: Control (substrate only), L. acidophilus, L. buchneri, L. reuteri, or an equal mixture of all three (107 cells/mL, final concentration). After 24 h of incubation (37°C, 160 rpm), samples were collected for pH and enumerations of total amylolytics, Group D Gram-positive cocci (GPC; Enterococci, Streptococci), lactobacilli, and lactate-utilizing bacteria. Enumeration data were log transformed prior to ANOVA (SAS, v. 9.3). Lactobacilli inhibited pH decline in corn and wheat fermentations (P < 0.0001). 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). Exogenous lactobacilli decreased amylolytics, while increasing lactate-utilizers in corn and wheat fermentations (P < 0.0001). In oat fermentations, L. acidophilus and L. reuteri inhibited pH decline and increased lactate-utilizers while decreasing amylolytics (P < 0.0001). For all substrates, L. reuteri additions (regardless of viability) had the lowest number of GPC and the highest number of lactobacilli and lactate-utilizers (P < 0.05). There were no additive effects when lactobacilli were mixed. Exogenous lactobacilli decreased the initial (first 8 h) rate of starch catalysis when wheat was the substrate, but did not decrease total (24 h) starch utilization in any case. These results indicate that exogenous lactobacilli can impact the microbial community and pH of cereal grain fermentations by equine fecal microflora ex vivo. Additionally, dead (autoclaved) exogenous lactobacilli had similar effects as live lactobacilli on fermentation. This latter result indicates that the mechanism by which lactobacilli impact other amylolytic bacteria is not simple resource competition.
Publication Date: 2017-03-30 PubMed ID: 28358885PubMed Central: PMC5373581DOI: 10.1371/journal.pone.0174059Google Scholar: Lookup
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- Journal Article
Summary
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The research investigates the impact of adding lactobacilli to the ex vivo fermentation of cereal grains by horse gut bacteria. It found that the added lactobacilli significantly altered the microbial community and fermentation pH, demonstrating the potential use of lactobacilli as probiotics in equine diets.
Background
- Horses’ diets often include cereal grains like corn, oats, and wheat. When the intake of starch from these grains exceeds the digestion capacity of the foregut, the excess starch will reach the hindgut and affect the microbial ecology.
- This research was carried out to study the implications of adding lactobacilli, a kind of bacteria often used in probiotics, to the fermentation process of grains by equine gut bacteria (microflora) ex vivo, which means outside the living body. The impact on pH and the growth of specific types of bacteria was studied over a 24-hour period.
Methods
- Fecal samples were collected from three mature geldings (castrated male horses) that were fed grass hay and given access to pasture.
- The fecal microbes were extracted, washed, and mixed with media containing the ground grains and one of five treatments: no addition (control), L. acidophilus, L. buchneri, L. reuteri, or a mix of all three bacteria.
- After incubation, samples were collected to measure pH levels and count populations of certain bacteria such as total amylolytics, Group D Gram-positive cocci (relating to strains of Enterococci and Streptococci), lactobacilli, and lactate-utilizing bacteria.
Findings
- Lactobacilli inhibited the decrease in pH during the fermentation of corn and wheat. L. reuteri and L. acidophilus were notably effective at controlling pH decline in corn and wheat fermentations.
- Exogenously added lactobacilli decreased the number of amylolytics while increasing the number of lactate-utilizers in corn and wheat fermentations. In oat fermentations, L. acidophilus and L. reuteri showed the same effect.
- For all grain types, the addition of L. reuteri resulted in the lowest number of Group D Gram-positive cocci and the highest number of lactobacilli and lactate-utilizers.
- No additive effects were noted when different lactobacilli were mixed together.
- The addition of lactobacilli slowed down the initial rate of starch catalysis when wheat was used as the substrate, but did not impact the total amount of starch utilized over the 24-hour period.
- Dead lactobacilli showed similar effects on fermentation as the live ones, suggesting that the impact of lactobacilli on other bacteria is not just simple resource competition.
Implications
- The findings from this study suggest that the addition of exogenous lactobacilli can significantly alter the microbial community and pH balance during grain fermentations by equine gut microflora.
- Given it doesn’t require the lactobacilli to be alive for them to have an impact implies that these bacteria may be used as probiotics in horse diets to modulate gut microflora, irrespective of their viability.
Cite This Article
APA
Harlow BE, Lawrence LM, Harris PA, Aiken GE, Flythe MD.
(2017).
Exogenous lactobacilli mitigate microbial changes associated with grain fermentation (corn, oats, and wheat) by equine fecal microflora ex vivo.
PLoS One, 12(3), e0174059.
https://doi.org/10.1371/journal.pone.0174059 Publication
Researcher Affiliations
- Department of Animal and Food Sciences, University of Kentucky, Lexington KY, United States of America.
- Department of Animal and Food Sciences, University of Kentucky, Lexington KY, United States of America.
- Equine Studies Group, WALTHAM Centre for Pet Nutrition, Melton Mowbray, Leicestershire, United Kingdom.
- Forage Animal Production Research Unit, Agricultural Research Service, United States Department of Agriculture, Lexington KY, United States of America.
- Department of Animal and Food Sciences, University of Kentucky, Lexington KY, United States of America.
- Forage Animal Production Research Unit, Agricultural Research Service, United States Department of Agriculture, Lexington KY, United States of America.
MeSH Terms
- Animal Nutritional Physiological Phenomena
- Animals
- Avena / chemistry
- Digestion / physiology
- Feces / chemistry
- Feces / microbiology
- Fermentation / drug effects
- Gram-Positive Cocci / chemistry
- Gram-Positive Cocci / metabolism
- Horses / microbiology
- Hydrogen-Ion Concentration
- Lactobacillus / chemistry
- Lactobacillus / metabolism
- Probiotics / chemistry
- Probiotics / metabolism
- Starch / chemistry
- Starch / metabolism
- Triticum / chemistry
- Zea mays / chemistry
Conflict of Interest Statement
BEH, LML, GEA and MDF declare no conflicts of interest. Patricia A. Harris is employed by one of the funders of this research (WALTHAM Centre for Pet Nutrition, Melton Mowbray, Leicestershire. LE14 4RT). The authors confirm that this does not alter their adherence to all the PLoS ONE policies on sharing data and materials.
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Citations
This article has been cited 2 times.- Chaucheyras-Durand F, Sacy A, Karges K, Apper E. Gastro-Intestinal Microbiota in Equines and Its Role in Health and Disease: The Black Box Opens. Microorganisms 2022 Dec 19;10(12).
- Boucher L, Leduc L, Leclère M, Costa MC. Current Understanding of Equine Gut Dysbiosis and Microbiota Manipulation Techniques: Comparison with Current Knowledge in Other Species. Animals (Basel) 2024 Feb 28;14(5).
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