Electromyographic evaluation of masseter muscle activity in horses fed (i) different types of roughage and (ii) maize after different hay allocations.
Authors: Vervuert I, Brüssow N, Bochnia M, Cuddeford D, Coenen M
Journal: Journal of animal physiology and animal nutrition
Summary
# Editorial Summary Vervuert and colleagues used electromyography to measure masseter muscle activity in horses consuming different forage types and concentrate feeds, examining whether diet composition and meal sequencing affected chewing mechanics. Four horses were monitored whilst fed hay, haylage, straw/alfalfa chaff, or cracked maize under various conditions; muscle action potential (MAP) amplitude and duration were recorded to quantify chewing intensity and cycle length. Roughage intake—whether hay (10±1.7V), haylage (11±3.3V), or straw/alfalfa chaff (13±3.8V)—generated sustained, forceful chewing with MAP durations around 0.22–0.31 seconds, whilst cracked maize was consumed rapidly with significantly lower muscle activation (6.0±1.5V), despite hay pre-feeding not altering subsequent concentrate consumption patterns. The practical relevance lies in recognising that concentrate-dominant diets elicit minimal jaw activity and therefore reduced salivary stimulation, potentially compromising the buffering capacity and digestive function of the stomach—a consideration particularly important when formulating high-energy diets or managing horses prone to gastric ulceration. Feeding strategies that prioritise adequate roughage intake, or restructuring meal sequences to maximise mastication before concentrate consumption, may help optimise salivary flow and gastric health.
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Practical Takeaways
- •Feeding roughage before concentrates promotes longer, more forceful chewing which stimulates salivary secretion—important for buffering gastric acid and maintaining digestive health
- •Concentrates like cracked maize are consumed too rapidly with minimal jaw muscle activity; always provide adequate roughage allocation to promote mastication and saliva production
- •Hay and haylage produce similar intensive chewing patterns and salivary flow benefits, making either suitable for maintaining proper digestive physiology regardless of fibre length
Key Findings
- •Hay and haylage intake produced intense masseter muscle activity (MAP 10-11 V, duration 0.30-0.31 s), while straw/alfalfa chaff showed higher amplitude (13 V) but shorter chewing cycle (0.22 s)
- •Cracked maize was consumed rapidly with significantly lower masseter muscle activity (MAP 6.0 V) compared to all roughage types
- •Prior hay intake, especially ad libitum feeding, prolonged chewing cycle duration for maize but did not affect chewing force intensity
- •Low salivary flow associated with concentrate consumption may adversely affect gastric function, whereas roughage-induced intensive chewing stimulates protective salivary flow