Alfalfa Chaff vs. Pellets: Can Form Affect Gastric Ulcers?
Alfalfa is a popular forage choice among horse owners for a variety of reasons. It comes in a variety of forms (such as hay, pellets, chaff, and cubes), delivers more nutrients than a grass hay, and has been shown to benefit horses suffering from gastric ulcers due to its natural buffering capacity.

However, little information exists on how alfalfa particle size affects the horse’s stomach. So, researchers from the University of Leipzig, in Germany, set out to investigate the effects of feeding two forms of alfalfa with different particle sizes versus a grass hay on weanlings’ gastric mucosa.

Prior to weaning, the team, led by Ingrid Vervuert, PhD, DVM, an assistant professor of veterinary medicine, introduced 39 male and 31 female Warmblood foals to a diet consisting of 3 kilograms (about 6.6 pounds) of alfalfa chaff, 3 kilograms alfalfa pellets, or ad libitum grass hay. The team provided all the foals with a special mix of oats, soybean meal, and/or a mineral supplement to ensure each treatment group had a similar nutrient intake. The team performed gastroscopies on the foals prior to weaning and after 16 days on their treatment diet to determine gastric ulcer prevalence and where the ulcers occurred within the stomach.

Using various-sized sieves, the team determined particle size for each alfalfa treatment:

  • 91% of alfalfa chaff particles were longer than 2 millimeters; and
  • 60% of alfalfa particles that made up the pellets were shorter than ¼ millimeter.

The team’s key takeaways:

  • 84.3% of foals had gastric mucosal lesions prior to weaning, and 100% had lesions 14 days post-weaning;
  • Most lesions were located in the squamous mucosa’s greater curvature and at the lesser curvature, both of which are located near the margo plicatus (the region that separates the glandular from nonglandular portions of the stomach; the glandular part of the stomach is protected by bicarbonate and mucus, while the nonglandular region remains unprotected and susceptible to damage from stomach acid and, thus, ulcers); and
  • Foals on the alfalfa chaff diet had more gastric mucosal lesions at the pylorus (where ingesta exits the stomach and enters the duodenum) than did the alfalfa pellet or grass hay-fed foals.

Contrary to the teams’ hypothesis, the alfalfa chaff resulted in more lesions at the pylorus than did the pellets, even though chaff is thought to increase chew time and saliva production, in turn buffering the stomach. The team believes this could be due to chaff’s course texture potentially injuring the pylorus during digestion.

Take-Home Message

Both nutrient components and buffering capacity make alfalfa a desirable forage choice for horses suffering from gastric ulcers. However, alfalfa chaff’s increased particle size could actually exacerbate lesions at the pylorus. As such, alfalfa products with smaller particle sizes appear to be more beneficial in terms of helping limit gastric lesion formation.

The study, “Effects of two alfalfa preparations with different particle sizes on the gastric mucosa in weanlings: alfalfa chaff versus alfalfa pellets,” was published in BMC Veterinary Research.