Food particle breakdown in herbivores : Influence of food intake level on energy yield
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Abstract
The quantitative relation between food intake level, comminution of the diet with teeth and the size of food particles in the gastro-intestinal tract (GIT), and the size of resulting effects on further digestive variables and therefore on food energy content for herbivores have been discussed controversially in the past. It can be assumed that at increasing intake level the rate of comminution of a diet and its retention time in the gastro-intestinal tract and in consequence its digestibility decrease. Results of this study confirm this and try to define this effect more precisely in a quantitative way. To date, studies on the correlation of faecal mean particle size (MPS) and food intake level have been conducted on domestic ruminants basically. They conveyed first reference points on the size of the change of chewing effectiveness per unit food intake level. For wildlife such an assertion is hard to make since data on the amount of diet ingested are rare. In the present study, this gap was approached in a literature review; a factor calculated from yield and energy content of milk allowed an estimation of the size of the difference between energy requirements during maintenance and during lactation. This factor was used to estimate the increase of faecal MPS during lactation, which is apparently influenced by body weight (BW) (between 8.5% for over 250 kg BW and 15.5% for under 100 kg BW).. In own studies, this effect was investigated in more detail for a small ruminant (goat). A maximum variation in food intake level was achieved by taking samples at different lactation stages. An increase of intake by one unit of maintenance intake caused an increase of MPS by 6 pecentage units while digestibility decreased by 4 percentage units and mean retention time of particles (MRTparticle) by 22 percentage units. Because comparable data for hindgut fermenters is absent, a trial was done with a small hindgut (caecum) fermenter (rabbit). Here no effect of doubling the intake level on faecal MPS could be noted while MRTparticle decreased by 39%. Using samples of different parts of the GIT (stomach, colon) the proportion of chewing on total food comminution in rabbits was estimated to be as high as ~98%.Link to publications or other datasets
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Giessen : VVB Laufersweiler