title: Effect of Dietary Starch Source and Concentration on Equine Fecal Microbiota.
abstract: Starch from corn is less susceptible to equine small intestinal digestion than starch from oats, and starch that reaches the hindgut can be utilized by the microbiota. The objective of the current study was to examine the effects of starch source on equine fecal microbiota. Thirty horses were assigned to treatments: control (hay only), HC (high corn), HO (high oats), LC (low corn), LO (low oats), and LW (low pelleted wheat middlings). Horses received an all-forage diet (2 wk; d -14 to d -1) before the treatment diets (2 wk; d 1 to 14). Starch was introduced gradually so that horses received 50% of the assigned starch amount (high = 2 g starch/kg BW; low = 1 g starch/kg BW) by d 4 and 100% by d 11. Fecal samples were obtained at the end of the forage-only period (S0; d -2), and on d 6 (S1) and d 13 (S2) of the treatment period. Cellulolytics, lactobacilli, Group D Gram-positive cocci (GPC), lactate-utilizers and amylolytics were enumerated. Enumeration data were log transformed and analyzed by repeated measures ANOVA. There were sample day × treatment interactions (P < 0.0001) for all bacteria enumerated. Enumerations from control horses did not change during the sampling period (P > 0.05). All treatments except LO resulted in increased amylolytics and decreased cellulolytics, but the changes were larger in horses fed corn and wheat middlings (P < 0.05). Feeding oats resulted in increased lactobacilli and decreased GPC (P < 0.05), while corn had the opposite effects. LW had increased lactobacilli and GPC (P < 0.05). The predominant amylolytic isolates from HC, LC and LW on S2 were identified by 16S RNA gene sequencing as Enterococcus faecalis, but other species were found in oat fed horses. These results demonstrate that starch source can have a differential effect on the equine fecal microbiota.
authors.affiliation: Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, 40546, United States of America.
authors.forename: Brittany E
authors.initials: BE
authors.lastname: Harlow
authors.affiliation: Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, 40546, United States of America.
authors.forename: Laurie M
authors.initials: LM
authors.lastname: Lawrence
authors.affiliation: Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, 40546, United States of America.
authors.forename: Susan H
authors.initials: SH
authors.lastname: Hayes
authors.affiliation: Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, 40546, United States of America.
authors.forename: Andrea
authors.initials: A
authors.lastname: Crum
authors.affiliation: Department of Animal and Food Sciences, University of Kentucky, Lexington, KY, 40546, United States of America.|Forage Animal Production Research Unit, Agricultural Research Service, United States Department of Agriculture, Lexington, KY, 40546, United States of America.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Flythe
mesh_terms: D000818:Animals; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D005243:Feces / Q000382:microbiology*; D005260:Female; D006736:Horses; D008297:Male; D064307:Microbiota; D013213:Starch / Q000008:administration & dosage*
chemical_list: D004040:Dietary Carbohydrates; D013213:Starch