Complete Extruded Diet - How Does Equine Fecal Microbiota Change During Intake Adaptation?

Sep 30, 2026

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This study investigated the gradual adaptation of the fecal bacterial community and in vitro fermentative capacity in horses fed a complete extruded diet (CED). Twelve geldings were initially kept on coastcross hay for 7 days, then allocated to hay-only (28 days) or stepwise CED inclusion (30%, 60%, 100%) replacing hay. Fecal samples were analyzed on Days 7, 14, 21, and 28. CED intake reduced several bacterial phyla while increasing Verrucomicrobia and Synergistetes; diversity stayed stable until Day 21 under intermediate CED but declined after full hay withdrawal.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages11

Reading Time28 min

AccessFree to download

Abstract

1 | Introduction

Background: pasture-to-concentrate transitions

Rationale for complete extruded diet (CED)

2 | Materials and Methods

2.1 | Ethics

2.2 | Animals

Animal Science Journal RESEARCH ARTICLE OPEN ACCESS Complete Extruded Diet: How Does Equine Fecal Microbiota Change During Intake Adaptation? Bruna Caroline Franzan1 | Irene da Silva Coelho2 | Emilly Martins Ramos1 | Ana Rúbia Pereira de Souza2 | Fernando Queiroz de Almeida2 | Vinicius Pimentel Silva1 1Animal Science Institute, Universidade Federal Rural do Rio de Janeiro, Rio de Janeiro, Brazil | 2Veterinary Institute, Universidade Federal Rural do Rio de Janeiro, Rio de Janeiro, Brazil Correspondence: Bruna Caroline Franzan ([bfranzan@ufrrj.br](bfranzan@ufrrj.br)) Received: 6 March 2025 | Revised: 23 September 2025 | Accepted: 11 December 2025 Keywords: concentrate meal | fermentation | fiber | hindgut | horse ABSTRACT This study aimed to investigate the gradual adaptation of the fecal bacterial community and in vitro fermentative capacity of horses fed a complete extruded diet (CED). Twelve geldings weighing 370 kg were removed from a native pasture and fed coastcross hay (Cynodon spp) for 7 days. In the second week, horses were assigned to two groups: one group was fed exclusively with coastcross hay (HAY) for 28 days and the other group fed with weekly increases of CED (30%, 60%, and 100%) to replace HAY. Fecal samples were collected on Days 7, 14, 21, and 28 for microbiota and in vitro fermentation analyses. CED intake reduces the relative abundance of phyla Fibrobacteres, Proteobacteria, Campilobacterota, Lentisphaerae, and SR1, while increasing Verrucomicrobia and Synergistetes. The fecal bacterial diversity was maintained until Day 21 (60% CED) but declined when hay was completely withdrawn. Equine fecal microbiota is diet-dependent; the stability of microbial diversity is more closely linked to the presence of roughage than to CED intake. Also, the inclusion of CED affects its microbial abundance and the detection of bacterial groups able to alter in vitro fermentative activity. 1 | Introduction The gastrointestinal microbiota of horses maintained at pasture undergoes natural changes, continuously adapting to variations in forage availability and quality driven by climatic and environmental factors (Salem et al. 2018; Fernandes et al. 2021) . Nowadays, the expansion of training centers near urban areas has reduced access to grazing land (Clarke et al. 1990) . This restriction also limits the area for storage of roughage foods since large areas are required for their adequate keep (NRC 2007) . Consequently, dietary and feeding management practices have adapted, including reducing fiber content of the diet and increasing grain-based processed feeds. Low-fiber intake combined with grain-based diets that supply excess starch can alter the composition and stability of the intestinal microbiota and affect the pH of the equine gastrointestinal tract (Coenen and Vervuert 2010; Hansen et al. 2015) . To address these challenges, high-fiber concentrates have been formulated to meet equines' daily nutritional requirements (Miraglia et al. 2006) to maintain the equine large intestine bacterial community. Within this context, the complete extruded diet (CED) could be used as an alternative for horse feeding. A CED is defined as the combination of all nutrients to supply the nutritional category requirements in a single product, except water (NRC 2007) . Although complete diets for feeding horses have been adopted for a long time (Earle 1950), there is some evidence that their adoption can provide good results in specific situations: greater weight gain in weaned foals (Andrew et al. 2006), improved feeding management for senior horses and those with dental problems due to the reduced particle size This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2026 The Author(s). Animal Science Journal published by John Wiley & Sons Australia, Ltd on beh

FAQs

How were horses assigned to the different diet groups during adaptation?

After an initial 7-day period on coastcross hay, horses were split into a hay-only group for 28 days or a CED group receiving weekly increases (30%, 60%, 100%) to replace hay.

Which fecal bacterial phyla changed with CED intake?

CED intake reduced the relative abundance of Fibrobacteres, Proteobacteria, Campilobacterota, Lentisphaerae, and SR1, while increasing Verrucomicrobia and Synergistetes.

When did fecal bacterial diversity remain stable, and when did it decline?

Diversity was maintained until Day 21 at the 60% CED level, but it declined when hay was completely withdrawn.

Sep 30, 2026

Uploaded by Muffet