Effect of a feed/fast protocol on pH in the proximal equine stomach.
Authors: Husted L, Sanchez L C, Baptiste K E, Olsen S N
Journal: Equine veterinary journal
Summary
# Effect of Intermittent Feed Deprivation on Equine Gastric pH Gastric squamous ulceration in horses is multifactorial in aetiology, but feed restriction and prolonged stall confinement are recognised risk factors; this study examined whether intermittent fasting protocols directly compromise the proximal stomach's acid buffering capacity compared to continuous feeding. Using a randomised cross-over design, six horses underwent two 72-hour periods with pH electrodes positioned at the oesophageal sphincter—one involving alternating 12/12-hour and 24/24-hour feed/fast cycles, the other with ad libitum access to hay and twice-daily concentrate—revealing that the interrupted feeding protocol produced significantly lower proximal gastric pH overall, though the difference was pronounced only during daylight and evening hours rather than overnight. A notable finding was that even continuously fed horses experienced a significant pH drop between 03:00 and 09:00 hours, suggesting an endogenous circadian rhythm independent of feeding status, and hay intake correlated positively with pH elevation. For practitioners, these results underscore that daytime feed deprivation rapidly exacerbates proximal acid exposure and should be avoided where possible, whilst acknowledging that nocturnal pH fluctuations occur physiologically regardless of management; this has particular relevance for weight management regimens and dry lot confinement protocols where feeding patterns are manipulated.
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Practical Takeaways
- •Avoid daytime feed deprivation in horses undergoing weight management, as proximal gastric acid exposure increases rapidly during daylight fasting periods
- •If feed restriction is necessary, consider scheduling fasting during nighttime hours when pH naturally decreases in fed horses anyway, rather than during day/evening
- •Maintaining consistent hay availability appears protective against low gastric pH; prioritize ad libitum forage access over intermittent feeding protocols when possible
Key Findings
- •Intermittent feed deprivation (12h fed/12h fasted/24h fed/24h fasted protocol) significantly lowered proximal intragastric pH compared to continuous feeding over 72 hours
- •pH differences between feed/fast and continuous feeding protocols were significant only during day and evening hours, not nocturnal hours
- •Proximal gastric pH decreased significantly from 03:00 to 09:00 h in continuously fed horses, showing spontaneous nocturnal pH reduction
- •Moderate positive correlation existed between hay intake and proximal gastric pH