Equine veterinary journal2026; doi: 10.1002/evj.70340

Forage chemical composition drives early metabolic shifts in ponies fed different haylages.

Moore-Colyer, MJS
·
Daniels, S
·
Harris, P

Abstract: Rapid changes between feeds can cause dysbiosis and colic in horses. The metabolic consequences of transitioning between haylages (HY) are currently unknown. Objective: To characterise urinary and faecal metabonomics in ponies transitioned between HY varying in botanical composition and physiological age and to evaluate the speed of metabolic adaptation. Methods: In vivo experiments repeated Latin Square. Methods: Eight Welsh Mountain ponies were fed four HY (R1, R2, M1, M2) across 4 × 15-day periods; a structured 3-day (Days 13-15) changeover was observed: old:new 70:30, 50:50and 30:70. Day 1 was 100% new haylage. Apparent digestibility was determined (multivariate mixed-effects model) from total faecal collections on Days 10-12. Urinary and faecal collections were performed on Days 0, 5, 12 and 14. Metabolic profiling of urine and faeces was performed using NMR spectroscopy with principal component analysis and orthogonal projections to latent-structures-discriminate analysis to identify metabolic shifts. Alignment and normalisation (total quotient method) were carried out in Mathworks Matlab R2014a. Conclusions: p ≤ 0.05. Results: Ponies achieved metabolic adaptation within 5 days. Metabolites were functionally stable at mid-changeover (Day 14). Forage chemical composition drove changes. Most significant differences were between physiologically young ryegrass haylage (R1) and the other three HY, for example, D5 urinary glycine R1 992 ± 504.4 vs. R2 222 ± 130. Faecal differences included altered faecal short-chain fatty acid plus amino-acid metabolites, for example, from Day 12 full adaptation to 5 days post-change for acetate: R114 ± 5.5, R2 19 ± 5.0; m-hydroxyphenol-acetate: R1 0.9 ± 0.22, M2 1.2 ± 0.63; indole-3-acetate: R1 1 ± 0.3, M2 2 ± 1.2. Conclusions: Ponies were only fed forage. Results may not reflect more abrupt changes between HY or between different forages. Conclusions: Metabolic adaptation to new HY occurred within the first 5 days and was shaped by forage composition. Three-day structured introduction supported metabolic stability. Metabonomics provides a sensitive, non-invasive tool and helps discriminate between forages for nutrient availability and hindgut function. Vigilance is still recommended in the first 5 days of introducing a new haylage.

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Publication Date: 2026-10-06 PubMed ID: 42838608DOI: 10.1002/evj.70340Google Scholar: Lookup

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Overview

This study examined how the chemical composition of different haylages affects early metabolic changes in ponies during feed transitions.
The research aimed to identify the speed and nature of metabolic adaptation using urinary and faecal metabonomics when ponies were switched between various haylages.

Study Background and Rationale

Rapid feed changes in horses can cause gut microbial imbalances (dysbiosis) and colic, a serious digestive condition.
Haylage (partially fermented forage) is commonly used but how metabolic processes respond to switches between different haylages is not well understood.
The study focused on ponies, investigating urinary and fecal metabolic profiles as indicators of gut and systemic metabolic state during transitions.

Methods

Experimental Design: A repeated Latin Square design was used involving eight Welsh Mountain ponies.
Haylages Tested: Four different haylages varied by botanical composition and physiological age – R1 (young ryegrass), R2, M1, and M2.
Feeding Periods: Each pony was fed each haylage for 15 days, with a structured changeover period during days 13-15 where the ratio of old to new haylage progressively shifted (70:30, 50:50, 30:70), and day 1 was 100% new haylage.
Sample Collection: Urine and feces were collected on Days 0, 5, 12, and 14 to track the metabolic response through the transition.
Apparent Digestibility: Determined from total fecal collections during days 10-12 to assess nutrient absorption.
Metabolic Profiling: Nuclear Magnetic Resonance (NMR) spectroscopy was used to analyze metabolite profiles in urine and feces.
Data Analysis: Techniques like principal component analysis (PCA) and orthogonal projections to latent-structures-discriminate analysis (OPLS-DA) identified changes in metabolic fingerprints related to different haylages.
Normalization: Data alignment and normalization were done using the total quotient method within Matlab software to ensure consistency.

Key Findings

Metabolic Adaptation Timing: Ponies showed metabolic adaptation to the new haylage within 5 days post transition.
Functional Stability: By mid-changeover (day 14), metabolic markers were stable, indicating successful adaptation.
Forage Composition Impact: Chemical composition of haylage was the primary driver of metabolic changes observed.
Distinct Haylage Differences:
- The young ryegrass haylage (R1) differed significantly in urinary and fecal metabolites compared to R2, M1, and M2.
- For example, day 5 urinary glycine was much higher for R1 (992±504.4) vs. R2 (222±130).
- Faecal short-chain fatty acids (e.g., acetate) and amino acid metabolites also varied strongly between R1 and others by day 12 and day 14, indicating differences in hindgut fermentation patterns.

Conclusions and Implications

Feeding only haylage means results might not apply to transitions involving other feed types or abrupt changes.
A three-day structured introduction to new haylage supports stable metabolic adjustment in ponies.
Metabonomics is a sensitive and non-invasive approach to discriminate forage quality and evaluate gut function.
Despite metabolic adaptation by day 5, careful monitoring is advised during the first 5 days when introducing new haylage to prevent potential health problems like colic.

Significance of the Research

This study provides important metabolic insights into how ponies adjust to different forage compositions at a biochemical level.
It highlights the importance of gradual feed transitions to minimize digestive disturbances.
The methods used can help in optimizing feeding strategies and improving equine health management related to diet changes.

Cite This Article

APA

Moore-Colyer MJS, Daniels S, Harris P. (2026). Forage chemical composition drives early metabolic shifts in ponies fed different haylages. Equine Vet J. https://doi.org/10.1002/evj.70340

Publication

Equine veterinary journal

ISSN: 2042-3306

NlmUniqueID: 0173320

Country: United States

Language: English

Researcher Affiliations

Moore-Colyer, M J S

Hartpury University, Gloucester, UK.

Daniels, S

The Royal Agricultural University, Gloucestershire, UK.

Harris, P

Equine Studies Group, Waltham Petcare Science Institute, Mars Horsecare, Leicestershire, UK.

Grant Funding

Mars Petcare

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