Supplementation of Ascorbic Acid in Weanling Horses Following Prolonged Transportation.

Sarah Ralston,Michelle Stives

doi:10.3390/ani2020184

Abstract

Simple SummaryHorses normally synthesize adequate amounts of ascorbic acid (vitamin C) in their liver to meet their needs for the vitamin. However, prolonged stress results in low plasma concentrations and reduced immune function. Weanling horses were supplemented with ascorbic acid for 5 or 10 days or no ascorbic acid (4 per group) following 50+ hours of transportation. Supplementation caused increases in plasma concentrations but both supplemented groups had decreased plasma ascorbic acid for 1 to 3 weeks following cessation of supplementation, possibly due to suppressed synthesis. Supplementation of ascorbic acid following prolonged stress will increase plasma concentrations, but prolonged supplementation should be avoided.Though horses synthesize ascorbic acid in their liver in amounts that meet their needs under normal circumstances, prolonged stress results in low plasma concentrations due to enhanced utilization and renal excretion and can reduce immune function. It was hypothesized that plasma ascorbic acid could be maintained in weanling horses by oral supplementation following prolonged transportation. Weanlings were supplemented with no ascorbic acid (Tx 0: n = 4), 5 grams ascorbic acid twice daily for 5 days (Tx 1: n = 4) or for 10 days (Tx 2: n = 4) following >50 hours of transportation. Supplementation caused slight (P < 0.2) increases in plasma ascorbic acid concentrations. Both supplemented groups had decreased (P < 0.05) plasma concentrations for 1 to 3 weeks following cessation of supplementation, possibly due to increased renal excretion or suppressed hepatic synthesis. Supplementation of ascorbic acid following prolonged stress will increase plasma concentrations, but prolonged supplementation should be avoided.

Highlights

There is very little information currently available about ascorbic acid (AA) supplementation in horses
On day 10 there was a numerical trend for plasma AA to be higher (P < 0.12) in treatment
The plasma AA concentrations reported in this study are somewhat higher than those reported in some other studies of normal, exercised and stressed horses [4,5,25,26] where values varied between

Summary

Introduction

There is very little information currently available about ascorbic acid (AA) supplementation in horses. The limited AA stores in the adrenal gland are mobilized by prolonged stressors such as transportation in horses and hepatic synthesis may be inadequate to maintain adequate plasma concentrations [3]. Supplementation of AA orally during training and following stress or illness in racehorses [4] and in competitive endurance horses [5] has proven to be an effective method for increasing plasma AA concentration. It has been documented to be ineffective in increasing plasma AA concentrations in unstressed horses [6]. In a preliminary study in this laboratory, prolonged supplementation (10 days) of AA to weanling horses that had been transported for 36 hours resulted in significant suppression of plasma AA for over 4 weeks after supplementation was stopped [7]

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Conclusion