Faecal particle size distribution in captive wild ruminants: an approach to the browser/grazer dichotomy from the other end

We investigated the particle size distribution in 245 faecal samples of 8 1 species of captive ruminants by a wet-sieving procedure. As a comparative measure, the modulus of fineness (MOF; Poppi et al. 1980) was used. Species were classified as frugivores (n=5), browsers (BR, n=16), intermediate feeders (IM, n=35) and grazers (GR, n=25). BR generally had a higher proportion of large particles, i.e. higher MOF values, than IM or GR of comparable size. These findings are in accord with reported lower fibre digestibility and less selective particle retention in BR, and are indicative of a difference in reticulo-ruminal physiology between the main ruminant feeding types. Possible consequences of the escape of larger particles from a browser's reticulo-rumen for the feeding of captive BR are briefly discussed

Comparative use of four different marker systems for the estimation of digestibility and low food intake in a group of captive giraffes (giraffa camelopardalis)

In a feeding trial with four captive giraffes, nutrient digestibility was determined using four different marker systems. Although cobalt-ethylenediaminetetraacetic acid proved to have no utility as a digestibility marker in this study, reasonable values could be obtained using C36 n-alkane, acid detergent lignin, and acid insoluble ash as markers. A comparison of methods and literature data suggests that the values derived from the C36 n-alkane assay are the most reliable absolute values. Apparent digestibility ranges thus determined were 63.5-74.3% for dry matter, 73.4-82.4% for crude protein, 49.9-62.2% for neutral detergent fiber, and 49.7-63.7% for acid detergent fiber. However, digestibility data gained by the ADL method provided the most stringent inter-individual comparisons. It is concluded that both alkanes and lignin can be used for giraffe digestibility studies. These captive giraffes ingested a smaller quantity of food than has been reported for other giraffes from both the wild and other zoos. Energetic calculations showed that these animals might be on the brink of an energy deficit. A similar situation has been described at least once before in captive giraffes, and the results are of direct relevance to the peracute mortality syndrome, a condition of captive giraffes in which severe depletion of body fat stores occurs. Reasons for the seemingly low food intake could not be elucidated, but observations suggested that these giraffes were ready to ingest more if more palatable or suitable food was offered. Monitoring food intake in other giraffe groups and designing a diet that is both palatable and nutritious are important objectives of captive giraffe management

Particle retention in the forestomach of a browsing ruminant, the roe deer capreolus capreolus

A combination of a flotation/sedimentation experiment and sieve analysis for the reticulorumen (RR) contents of roe deer Capreolus capreolus Linnaeus, 1758, a browsing ruminant, showed that there was no correlation between particle size and particle density. Large particles were present in both the sedimented and the buoyant fraction, which is in accord with the reported absence of stratification of RR contents in browsing ruminants. Comparative sieve analysis of roe deer RR and caecal/rectal material demonstrated that there must be some selective particle retention in the browsing ruminant as well, as a certain fraction of large particles in RR contents does not occur in the caecal/rectal material. These results lead to the explanatory dilemma that, while selective particle retention is observed, it cannot be due to the mechanisms known to work in grazing ruminants

Ruminant diversification as an adaptation to the physicomechanical characteristics of forage. A reevaluation of an old debate and a new hypothesis

The validity of Hofmann's classification of ruminants into browsers/"concentrate selectors", intermediate feeders and grazers/"grass and roughage eaters" and of his consecutive physiological postulates has repeatedly been questioned. In contrast to former concepts, which all focused on the chemical characteristics of the respective forages, we propose a new hypothesis on the main driving force of ruminant diversification, namely the physicomechanical characteristics of the respective forages. In contrast to browse, grass tends to stratify and form a "fibrous raft" in the reticulorumen. The significantly more capacious forestomachs of grazers, and the significantly thicker rumen pillars (indicating the strength of reticulorumen muscle equipment) of their forestomachs, are interpreted as particular adaptations to this forage characteristic. With these parameters, we present, for the first time, two single morphological measurements that allow the statistical reconstruction of Hofmann's classification. A small forestomach capacity and the lack of strong reticulorumen muscles in browsers would explain the observed exclusiveness with which browsers avoid grass forage under natural conditions, which we confirmed using two datasets on the composition of the natural diet. Both rumen pillar thickness and relative forestomach capacity were significantly correlated to the grass content of the natural diet, respectively. Our functional interpretation was also supported by a stepwise regression analysis with the proportion of grass in the natural diet as dependent variable and the rumen pillar thickness, the relative forestomach capacity, and the body weight as independent variables, which revealed significant equations