The physiological process of particle breakdown commences with mastication during food intake. In ruminants intake behaviour has been measured extensively as an indicator for diet selection and apparent palatability of feedstuffs [1,4]. Short-term intake behaviour can also used as a long-term predictor of food intake and for its contribution to fragmentation of plant structures for nutrient release. Although equids cannot re-masticate feed and their digestive physiology predisposes particles to much less efficient breakdown [3], little research on ingestive behaviour and its effects has been done.

Nine horses, with no previous experience of lucerne products, were offered short chopped high temperature dried lucerne (DL; 0.87 DM) and short chopped lucerne silage (LS; 0.39 DM) in three phases using a latin square design (Phase 1: 400g DL, Phase 2: 400g LS; Phase 3: 400g DL and 400g LS). An ethogram was developed to record behaviour patterns for analysis of transition matrices and choice-selection behaviour. Three classifications of behaviour were identified: 'Olfactory/Sensory Response': sniffing, nibbling, nodding, blowing, 'Feeding': bites, chewing in trough, chewing out of trough, licking; and 'Rejection': moves away (Figure 1). Intake behaviour was also measured by recording short-term intake rates (STIR; chews min^-1; chews bite^-1, chews kg^-1 DM and intake min^-1).

A visual representation of intake behaviour, using timed sequential data of each behaviour pattern was produced with a specially constructed computer programme [2]. From this 'Olfactory/Sensory Response' increased significantly when LS was offered (p<0.01) and preference of ingestion to DL occurred (p<0.01; Figures 1a-c).

Stir data confirm this with a chewing rate of 30.57 (s.e. 4.69) and 54.04 (s.e. 2.14) chews/min for DL and LS respectively (p<0.01). Intake rate was significantly higher for DL (91.1 g DM/min, s.e. 5.38, LS: 37.29, s.e. 3.61; p<0.001).

Figure 1. Ethograms for one horse fed (a) dried lucerne, (b) lucerne silage, (c) choice of both.

References

1. Chambers, A.R.M.; Hodgson, J.; Milne J.A. (1981). The development and use of equipment for the automatic recording of ingestive behaviour in sheep and cattle. Grass and Forage Science, 36, 97-105.
2. Davidson, C.R. (2000). Ethogram-er, Outware Education, Outware Association Ltd., UK.
3. Ellis, A.D.; Hill, J. (1999). Comparison of particle size reduction of a hay-concentrate diet given to horses and sheep. Proceedings of the British Society of Animal Science, p.143
4. Penning, P.D.; Parsons, R.J.; Orr, R.J.; Hooper, G.E. (1994). Intake and behaviour responses by sheep to changes in sward characteristics under rotational grazing. Grass and Forage Science, 49, 476-486.

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