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Translational animal science2023; 9; txad003; doi: 10.1093/tas/txad003

Impact of a 24 h feed withdrawal on active nutrient transport, intestinal morphology, and gene expression in the equine small and large intestine.

Abstract: Horses are often subjected to short-term feed withdrawal (FW) pre- or post-surgery to reduce anesthetic complications. However, removing nutrients from the intestinal lumen may negatively impact intestinal health. Thirteen horses were used to determine the effects of a 24 h FW on gut barrier function, active nutrient transport, transporter gene expression, and intestinal morphology. Following 0 or 24 h FW (0FW or 24FW, respectively), horses were euthanized via overdose of sodium pentobarbital and sodium phenytoin, and segments of proximal jejunum (PJ), mid jejunum (MJ), ileum (Il), and right ventral colon (RVC) were harvested for histology (PJ and Il), gene expression, and active nutrient transport analysis. Active transport measurements were determined using modified Ussing chambers following the addition of glucose, phosphorus, glutamine, and Gly-Sar. Carbachol-induced chloride (Cl) ion secretion was measured to examine the diarrhetic response. Messenger RNA expression of the intestinal Na-dependent glucose cotransporter (SGLT1), fructose transporter (GLUT5), di- and tri-peptide transporter (PepT1), and neutral AA/glutamine transporter (ASCT2) were determined using RT-PCR. The GLM procedure of SAS was used to determine the effects of FW and responses among various intestinal sections. The horse served as the experimental unit. Villus heights ( < 0.002) and crypt depths ( < 0.02) in the Il were larger than in the PJ, though no differences were observed between 0FW and 24FW horses. Active glutamine absorption increased 82% in the PJ of 24FW horses compared to 0FW horses ( < 0.02). The mRNA expression of SGLT1 decreased ( < 0.05), moving aborally in the gastrointestinal tract. Horses subjected to 24FW had 82% less GLUT5 ( < 0.05) and 61% less PepT1 mRNA expression in the PJ, compared to 0FW horses. Interestingly, ASCT2 mRNA expression increased 164% from PJ to RVC ( = 0.05). However, a 36% decrease in ASCT2 mRNA expression was observed overall for 24FW horses. These data indicate that SGLT1, GLUT5, PepT1, and ASCT2 are expressed throughout the small intestine and RVC of the horse at varying concentrations and that they can be differentially regulated by a 24 h FW. Data from this experiment also indicate that a 24 h FW results in up regulation of active glutamine absorption, presumably in an effort to supply glutamine as an energy substrate for enterocytes.
© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science.
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Publication Date: 2023-01-28 PubMed ID: 40041718PubMed Central: PMC11879028DOI: 10.1093/tas/txad003Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study investigated how a 24-hour feed withdrawal (FW) affects nutrient transport, intestinal structure, and gene expression in different parts of the horse’s small and large intestine.
  • The goal was to understand the impact of short-term fasting, often used before or after surgery, on gut health and nutrient absorption in horses.

Background and Purpose

  • Horses commonly undergo short-term feed withdrawal to decrease risks associated with anesthesia during surgical procedures.
  • However, removing nutrients from the gut could potentially impair intestinal health by affecting nutrient absorption and gut barrier function.
  • This study aimed to evaluate the effects of a 24-hour feed withdrawal on:
    • Active nutrient transport mechanisms
    • Intestinal morphology (villus height and crypt depth)
    • Expression levels of genes encoding nutrient transporters in various intestinal regions

Experimental Design and Methods

  • Thirteen horses were divided into two groups: one with no feed withdrawal (0FW) and one with 24 hours of feed withdrawal (24FW).
  • After the treatment, horses were euthanized, and tissue samples were collected from four intestinal regions:
    • Proximal jejunum (PJ)
    • Mid jejunum (MJ)
    • Ileum (Il)
    • Right ventral colon (RVC)
  • Histological analysis was performed on the PJ and Il samples to measure villus height and crypt depth.
  • Active nutrient transport was assessed using modified Ussing chambers measuring uptake of compounds like glucose, phosphorus, glutamine, and Gly-Sar (a dipeptide analog).
  • The response to carbachol-induced chloride ion secretion (a proxy for diarrhetic response) was also measured.
  • Gene expression of nutrient transporters was quantified by RT-PCR for the following transporters:
    • SGLT1 – sodium-dependent glucose transporter
    • GLUT5 – fructose transporter
    • PepT1 – di- and tri-peptide transporter
    • ASCT2 – neutral amino acid/glutamine transporter
  • Statistical analysis was conducted using the GLM procedure of SAS, with each horse as the experimental unit.

Key Findings: Intestinal Morphology

  • The ileum displayed significantly larger villus heights and crypt depths compared to the proximal jejunum (villus height p < 0.002, crypt depth p < 0.02).
  • No significant differences in these morphological parameters were observed between horses that underwent feed withdrawal and those that did not, indicating 24 hours without feed does not impair intestinal structure measurably.

Key Findings: Active Nutrient Transport

  • Active glutamine absorption increased by 82% in the proximal jejunum of horses after 24 hours of feed withdrawal compared to controls (p < 0.02).
  • This suggests that glutamine transport is upregulated during feed withdrawal, possibly to provide enterocytes (intestinal cells) with an alternate energy source during nutrient scarcity.

Key Findings: Gene Expression of Nutrient Transporters

  • SGLT1 (glucose transporter) mRNA expression decreased progressively moving aborally (down the gut from PJ to RVC) (p < 0.05).
  • In feed withdrawal horses (24FW):
    • GLUT5 (fructose transporter) mRNA levels in the proximal jejunum dropped by 82% compared to controls (p < 0.05).
    • PepT1 (peptide transporter) mRNA was reduced by 61% in the same region (p < 0.05).
    • ASCT2 (neutral amino acid/glutamine transporter) mRNA increased by 164% from the proximal jejunum to right ventral colon (p = 0.05) across all horses.
    • However, overall ASCT2 expression decreased by 36% in the 24-hour feed withdrawal group.
  • These results show that nutrient transporter genes are present along the small and large intestine but their expression is modulated differently by short-term fasting.

Interpretation and Biological Significance

  • A 24-hour feed withdrawal:
    • Does not appear to compromise intestinal structure microscopically.
    • Increases active absorption of glutamine, an important energy substrate for intestinal cells, indicating a likely protective or adaptive mechanism during nutrient scarcity.
    • Downregulates gene expression of certain sugar (GLUT5), peptide (PepT1), and amino acid (ASCT2) transporters, possibly reflecting decreased demand or availability for those nutrients.
    • Maintains expression of glucose transporter SGLT1 but with a gradient decrease down the intestine.
  • These changes suggest a coordinated intestinal response to fasting that helps maintain gut barrier function and energy supply during periods without feed.
  • This information is important for veterinarians managing equine surgical patients and understanding how brief feed restriction impacts gut physiology.

Conclusions

  • Short-term (24 h) feed withdrawal in horses does not harm intestinal morphology but causes distinct changes in nutrient transporter gene expression and nutrient absorption.
  • An adaptive increase in glutamine absorption may help support enterocyte energy needs during fasting.
  • These findings provide insight into the gut’s response to planned feed withdrawal and may guide management strategies to optimize intestinal health in clinical settings.

Cite This Article

APA
Aldridge-Dean BE, Lescun TB, Radcliffe JS. (2023). Impact of a 24 h feed withdrawal on active nutrient transport, intestinal morphology, and gene expression in the equine small and large intestine. Transl Anim Sci, 9, txad003. https://doi.org/10.1093/tas/txad003

Publication

Translational animal science
ISSN: 2573-2102
NlmUniqueID: 101738705
Country: England
Language: English
Volume: 9
Pages: txad003
PII: txad003

Researcher Affiliations

Aldridge-Dean, Blaire E
  • BSM Partners, Bentonville, AR 72712, USA.
Lescun, Timothy B
  • Department of Veterinary Clinical Sciences, Purdue University, West Lafayette, IN 47907, USA.
Radcliffe, John Scott
  • Department of Animal and Food Science, University of Kentucky, Lexington, KY 40546, USA.

Conflict of Interest Statement

None declared.

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Citations

This article has been cited 1 times.
  1. Austin MMP, Ivey JLZ, Shepherd EA, Myer PR. Methodologies to Identify Metabolic Pathway Differences Between Emaciated and Moderately Conditioned Horses: A Review of Multiple Gene Expression Techniques.. Animals (Basel) 2025 Oct 10;15(20).
    doi: 10.3390/ani15202933pubmed: 41153862google scholar: lookup
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