|HARLOW, BRITTANY - University Of Kentucky|
|LAWRENCE, LAURIE - University Of Kentucky|
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., Flythe, M.D. 2015. Effect of inulin chain length on fermentation by equine fecal bacteria and Streptococcus bovis in vitro. Proceedings of the Equine Science Society. 35:425.
Technical Abstract: The ingestion of large quantities of rapidly fermentable carbohydrates (e.g. fructans) from pasture has been associated with the development of laminitis. Fructans are poorly degraded by mammalian enzymes and, therefore, are able to reach the hindgut. The fermentation of fructans can lead to the overgrowth of Gram-positive bacteria (Streptococcus bovis), increasing lactic acid production and decreasing hindgut pH. Cool season grasses can accumulate high concentrations of fructans, varying with plant species and environmental conditions. Furthermore, the degree of polymerization (DP) of fructans has been suggested to influence fermentation rates. The current study was conducted to evaluate the effect of short chain or long chain inulin (model fructan) on pH and growth of S. bovis. For pH experiments, feces were collected on different days from 3 mature mares fed hay. Fecal microbes were harvested by differential centrifugation, washed, and re-suspended in anaerobic media containing either short chain inulin (SC; Orafti OPS; DP = 10) or long chain inulin (LC; Orafti HP; DP = 23) from 0-2% w/v, in 0.1% increments. After 24 h of incubation (37 ºC, 160 rpm) samples were collected for pH. Data were analyzed using the ANOVA procedure of SAS (v. 9.3). At all inulin concentrations tested, the pH was lower in SC fermentations than in LC at 24 h (P <0.0001, in all cases). Based on these results, 3 concentrations of inulin were selected for use in the growth experiment: 0.1%, the lowest concentration eliciting effects on pH; 0.5%, the concentration with the greatest difference in pH between LC and SC (0.32 pH units); and 1.3%, the minimum concentration eliciting maximal pH effects in both LC and SC. For growth experiments, each bottle was inoculated (1% w/v) with stationary phase S. bovis and incubated (39 ºC) for 9 h with 0.1, 0.5, or 1.3% SC or LC inulin. Optical density was determined by spectrophotometry (600 nm) every 30 min to monitor bacterial growth. Growth rates were determined by linear regression (2-5 h). The growth rate of S. bovis on 0.1, 0.5 and 1.3% inulin were 8.2×, 2×, and 1.1× faster during the exponential phase with SC than LC, respectively (P < 0.0001, in all cases). Also, after 9 h of incubation, the final OD was 34%, 92% and 164% higher in SC than LC, at 0.1, 0.5, and 1.3%, respectively (P < 0.0001, in all cases). These results indicate that SC inulin may be more available for rapid fermentation than LC inulin by equine fecal bacteria, including S. bovis.