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EQUINE VETERINARY EDUCATION / AE / JANUARY 2017
NSC diets are fed. In addition, ingestion of a grain meal resulted in higher serum gastrin concentration when compared to ingestion of grass hay (Smyth et al. 1989; Sandin et al. 1998). Gastrin is the only hormone known to stimulate secretion of HCl, and rations that contain more readily available nutrients, such as pellets and sweet feed, produce a significant increase in post prandial gastrin concentrations (Sandin et al. 1998). In addition, grain feeding was shown to delay gastrin secretion, which corresponded to an increase in gastric acid secretion after the stomach had emptied the grain contents (Sandin et al. 1998).
Forage type In previous studies, feeding alfalfa hay and grain compared to brome grass hay without grain in exercising horses appeared to have a protective effect on the squamous mucosa (Nadeau et al. 2000; Lybbert et al. 2007). In the earlier study, horses fed alfalfa hay and grain had a higher stomach pH and lower squamous ulcer scores when compared with horses fed brome grass hay without grain (Fig 1). It has been suggested that calcium and protein, both high in the alfalfa hay, buffer stomach contents, resulting in a protective effect on the squamous mucosa. It should be noted that, in these studies, gastric juice VFA concentrations were significantly higher after feeding alfalfa hay and grain (‘sweet feed’), but because of the higher stomach pH the VFAs were likely not readily lipid soluble (Nadeau et al. 2000). In contrast, a recent study showed that squamous ulcers were more severe in weanling foals fed alfalfa chaff (plus oats), which might have been due to the small particle size or due to mechanical damage due to the chopped edges in this alfalfa chaff (Pfaff et al. 2015). Diets containing restricted levels of NSC (‘low-starch’ feeds), may result in lower gastric juice concentrations of VFA after feeding and reduced adverse effects on the squamous mucosa sodium transport. In addition, feeding straw (rather than hay or haylage) as the sole source forage increased the risk of squamous ulcers >4-fold and the authors suggested this could have been due to the low protein and calcium content of straw, as well as its physical form (Luthersson et al. 2009).
Particle size Work in pigs has suggested that feeding a high proportion of the daily diet as very finely ground pellets (particle size <0.4 mm) increases the risk of gastro-oesophageal ulcers (Liesner et al. 2009; Cappai et al. 2013; Pfaff et al. 2015). This has not been specifically evaluated in the horse but is unlikely to be a risk other than in animals (e.g. older horses with no teeth) fed a complete pelleted diet which is very finely ground. Besides, many pelleted completed diets have alfalfa as a base ingredient, which might be protective.
Clinical signs
Clinical signs commonly associated with EGUS are numerous but often vague and associated with lesions in the squamous mucosa. Some clinicians generally consider EGUS ulcer grade 1 (hyperkeratosis/hyperaemia) or 2 (small single or multifocal ulcers) lesions unlikely to cause clinical signs, whereas EGUS ulcer grades 3 (large focal or multifocal ulcers) and 4 (large extensive often coalescing ulcers) are most likely to lead to clinical signs (Sykes and Jokisalo 2015). However, there is a
© 2015 EVJ Ltd
0 1 2 3 4 5 6
a a a b a a b b b
Alf/gra Brome
012345678 10 Time (h)
12 24
Fig 1: Mean ( s.e.m.) pH of the gastric juice when 6 horses were fed a diet of alfalfa hay and grain (0.5 kg/100 kg bwt;
squares) and when they were fed a diet of brome grass hay (triangles). Time 0 represents sample collected immediately after horses completed their feed. Values with different lower case letters differ significantly (P≤0.05).
lack of supporting evidence of this, as the prevalence of squamous gastric ulcers in horses is high, yet overt clinical signs are lacking regardless of the ulcer score (Begg and O’Sullivan 2003; Dionne et al. 2003; Marqu
es et al. 2011;
Malmkvist et al. 2012). In one study, 53% of horses, not in active training and considered normal by their owners and trainers, had a squamous EGUS ulcer score ≥2/4 (Luthersson et al. 2009). However, squamous (or glandular) ulcers might produce clinical signs that are often vague and might be missed by owners and trainers. This was the situation in 4 horses in which poor performance, after ruling out other causes, improved significantly after appropriate antiulcer therapy (Franklin et al. 2008). In these cases, treatment resulted in an overall improvement in performance and of squamous ulcer scores. However, ulcers tend to be more commonly diagnosed in horses showing overt clinical signs. For example, squamous ulcers were identified in 92% of horses with a client complaint of conditions associated with ulcers or horses showing subtle signs of poor health, compared with 52% identification in horses not showing signs; however, the pyloric antrum was not observed in the study (Murray et al. 1989). In addition, epidemiological observations of Thoroughbred horses in race training revealed that squamous ulcers might be associated with poor performance, poor hair coat, picky eating and colic, and ulcer severity was correlated with the degree of poor performance and clinical signs (Vatistas et al. 1999a). In addition, horses with squamous ulcers exercising on a treadmill showed a significantly shorter time to fatigue, had a shorter stride length and consumed more oxygen than horses without gastric ulcers after 56 days (Nieto et al. 2009). Overall, horses without squamous ulcers increased their aerobic capacities by a greater amount when compared to horses with ulcers. Horses with a low body condition score (BCS) in 2 studies
had more ulcers than horses with a good BCS (Lester et al. 2007, 2008) which could either reflect the clinical consequence of the squamous ulcers or that marginal to poor nutrition contributes to the cause and maintenance of squamous ulcers in horses. However, in another small study in Spanish horses those with BCS 6–7/9 had a mean squamous EGUS score 1.44 units higher than horses with BCS 4–5/9 (Luthersson et al. 2011) although other environmental factors may have influenced this.
b
pH
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