Table 1.

Main effects of high starch diet on hindgut microbiota.

Reference	Type of Diet and Protocol Details	Effect on Microbiota
[61]	4 fistulated horses in a 4 × 4 latin square design. Diets fed 2×/day. HF = 11.6% starch; 41% NDF HS = 30.1% starch; 30.7% NDF NDF:starch ratio of 3.5 for HF and 1.0 for HS diets Enumeration of cultivable viable functional bacterial groups in the cecum and colon	Increase in Lactobacilli in the cecum and the colon with HS diet but no change in total anaerobes, cellulolytics or streptococci
[60]	8 fistulated horses in a 4 × 4 latin square design. Diets fed 2×/day HS = 3.4 g/kg BW of starch per meal but maintaining NDF:starch ratio of 1.0 Enumeration of cultivable viable functional bacterial groups in the cecum and colon	With HS, total anaerobic and lactic acid-utilizing bacteria increased, and cellulolytic bacteria decreased in the cecum. Increase in lactobacilli and streptococci both in the cecal and colonic contents
[19]	17 mares Hay diet vs. hay plus a high cereal supplement (35% of starch in the high starch diet) 16S rDNA sequencing	With starch diet, increase in Proteobacteria phylum (Succinivibrio/Succinivibrionaceae related OTUs) Increase in Phocaeicola related OTU (Bacteroidetes phylum), increase in some Lachnospiraceae related OTUs but decrease in other Lachnospiraceae related OTUs (Firmicutes phylum)
[66]	6 fistulated geldings in a 2 × 2 latin square design. Diets fed HS = 56%/44% hay/barley diet for 3 weeks (0.20% BW of starch per meal) HF = 100% hay 16S rDNA sequencing Enumeration of cultivable viable functional bacterial groups in the cecum and colon	Reduced bacterial diversity with HS Impact of HS diet on community composition: decrease in Ruminoclostridium genus in the cecum, decrease in Bacteroidales S24-7 and, Lachnospiraceae NC2004 groups, increase in Veillonellaceae family in the colon Total anaerobes, starch utilizers, lactate utilisers increased, and cellulose utilizers decreased
[65]	Ten 18-month-old ponies in a 2 × 2 cross-over design with 2 experimental diets HF and HS. Diets fed 2×/day. HF = hay and lucerne; 0.46 g/kg of BW of starch per meal HS = hay and compound mix; 0.96 g/kg BW of starch per meal 16S rDNA sequencing in the feces	Bacterial diversity lower in HS diet with higher variance Impact of HS diet on community composition: decrease in Ruminococcaceae family abundance and increase in Streptococcus OTU
[18]	23 pony mares of different ages followed for 2 years HF: Hay diet at 2% body mass as daily dry matter intake for 4 weeks HS: 2 g starch per kg body mass distributed for maximum 5 days 16S rDNA sequencing in the feces	Diet transition increased Candidatus, Saccharibacteria and Firmicutes phyla abundance and reduced Fibrobacteres abundance At the genus level: Streptococcus abundance increased but not consistently across individual animals. Fecal pH and SCFA concentrations modified by diet but considerable inter-individual variation