The objective of this study was to evaluate the effect of a commercial feed supplement containing pectin-lecithin on squamous mucosa ulceration in horses exposed to an experimental ulceration model. Five mares were treated while five mares were controls for this crossover, blinded study. The mares were fed concentrates and hay and were stabled with a two-hour turn out per day for a period of four weeks. The pectin-lecithin complex was fed for the duration of the study on the treated group. At the end of a four-week period, all mares underwent a seven-day alternating feed deprivation (week 5). The study was repeated again after a four-week washout period. Gastroscopy was performed on days 1, 28 and 35 of the study and was digitally recorded. Independent evaluation of the recordings and scoring of the lesions using the Equine Gastric Ulcer Syndrome (EGUS), severity and number scores were performed by three experienced gastroscopists. The prevalence and severity of squamous ulcers significantly increased after intermittent feed deprivation (P<0.001). No significant effect of the treatment was observed (P>0.05). In this study, the addition of a commercially available pectin-lecithin complex to the feed of horses for five weeks did not prevent or minimise the risk for gastric ulceration of the squamous mucosa.