The influence of molar occlusal surface area on the voluntary intake, digestion, chewing behaviour and diet selection of red deer (Cervus elaphus)

Abstract

The loss of tooth effectiveness due to molar wear has been proposed as an important cause of mortality in ungulate populations. Voluntary intakes, digestibility, mean retention times, chewing behaviour (during eating and rumination), and diet selection (physical selection: short vs long particles in hay; and botanical selection: leaf vs stem) were compared in two groups of female red deer (Cervus elaphus) which differed in molar occlusal surface area, in order to test the hypothesis that behavioural and physiological mechanisms can be used to maintain assimilation efficiency in the presence of low functional tooth effectiveness. The group with lower values for first lower molar occlusal surface area (OSA) corrected for body weight had lower voluntary food intakes (P = 0.0126). The low OSA group had a greater number of chews per g DM of food ingested (P = 0.0167), a greater time spent chewing (P = 0.0476) but a lower number of chews per min than did those with a high OSA (P = 0.0484). The total number of chews per day was similar for both groups (P = 0.2011). The number of ruminating chews per day was less for the low OSA group (P = 0.0377). The group with low OSA values had a larger average particle size in their faeces (P = 0.0346). No differences were detected between groups in the physical or botanical composition of the diet selected (P = 0.3030, P = 0.3056, respectively) or in total digestibility and mean retention times (P = 0.1357, P = 0.3464, respectively). As a consequence of the lower voluntary intake the low OSA group had a lower digestible dry matter intake (P = 0.0170). This study supports the view that intake modification and the time invested in chewing during eating are the main mechanisms used to compensate for reduced chewing effectiveness associated with changes in tooth morphology, although the compensation is not total.