Comparative investigations on digestion in grazing (Ceratotherium simum) and browsing (Diceros bicornis) rhinoceroses

Institute of Animal Science, University of Bonn, 53115 Bonn, Germany.
Comparative biochemistry and physiology. Part A, Molecular & integrative physiology (Impact Factor: 1.97). 03/2010; 156(4):380-8. DOI: 10.1016/j.cbpa.2010.03.006
Source: PubMed


Rhinoceroses represent the largest extant herbivores with extensive dietary specialization for plant groups like browse (black rhino Diceros bicornis) or grass (white rhino Ceratotherium simum). However, it is not clear to what extent such diet selection patterns are reflected in adaptations of digestive physiology of the respective feeding types. In this study, feeding trials with four black and five white rhinos were conducted in four zoos. The animals had ad libitum access to the same batch of grass hay (second cut; neutral detergent fiber (NDF) 63% dry matter (DM), crude protein 10.2% DM). Total intake, fecal N content, in vitro digestibility of NDF residues of feces, fecal particle size and mean retention time (MRT) of particles (Cr-mordanted fiber; 1-2mm) and fluid (Co-EDTA) were quantified. The average daily DM intake was 70+/-12 g/kg BW(0.75) for white and 73+/-10 g/kg BW(0.75) for black rhinos. In the in vitro fermentation test fecal NDF residues of black rhinos resulted in higher gas productions at fermentation times of 12 to 24h, indicating that white rhinos have a superior capacity to digest NDF. Average MRT for fluids and particles was 28+/-4h and 43+/-5h in white and 34+/-4h and 39+/-4h in black rhinos. The selectivity factor (SF=MRT(particle)/MRT(fluid)) was higher for white (1.5+/-0.2) than for black rhinos (1.2+/-0.1) (p=0.016). In a comparison of 12 ruminant and 3 rhino species, SF was correlated to percentage of grass in diet (R=0.75). Mean fecal particle size was higher in white (9.1+/-1.94 mm) than in black rhinos (6.1+/-0.79 mm) (p=0.016). The results demonstrate differences between white and black rhinos in terms of retention times and fiber digestibility. The more selective retention of particles by the white rhino corresponds with the higher digestion of fiber measured indirectly. Furthermore there is indication for a general pattern of high SF in grazing ruminants and rhinos. The difference in fecal particle size between both rhino species might be due to the considerable difference in body weight.

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    • "It has been suggested that a higher degree of digesta washing removes microbes faster from the fermentation chamber and hence selects for a microbial population that grows faster and is metabolically more active and efficient (reviewed in Clauss et al., 2010a; Müller et al., 2011). This matches the observation that high SF are linked to grass intake (Clauss et al., 2006, 2010b; Steuer et al., 2010), because grass contains comparatively high levels of digestible, yet slowly-digestible, fibre (Hummel et al., 2006). Yet, more experimental work on the relationships between various aspects of digestive physiology and digestibility proxies is required before such hypotheses can be accepted. "
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    ABSTRACT: In herbivore ecophysiology, comparative chewing efficiency has only recently received increased attention. This measure is best assessed on un-processed forage-only diets; corresponding comparative datasets are missing. We measured a faecal mean particle size (MPS [mm]) in 14 large herbivore species (body mass (M) range 60-4000kg; 8 ruminants and 6 hindgut fermenters) fed a consistent grass hay diet, in which intake, digesta mean retention times (MRT [h]) and digestive efficiency (as digestibility of faecal fibre measured by 96h cumulative in vitro gas production GP96h [ml per 200mg faecal fibre], and metabolic faecal nitrogen MFN [% organic faecal matter]) had been quantified simultaneously. MPS was generally lower in ruminants than in hindgut fermenters and increased with M in the total dataset, but was nearly constant among closely related taxa (e.g. within ruminants, within equids) irrespective of M. MPS (but not MRT) was significantly correlated to GP96h, whereas MRT (but not MPS) was significantly correlated to MFN, suggesting different effects of these factors on different aspects of digestibility. Combinations of measures including MPS mostly explained digestibility better than other combinations. The phylogenetic signal λ, which was mostly 1 when linking any single measure to digestibility, was estimated 0 in models that linked digestive efficiency to combinations of measures. These results support the intuitive concept that species diversification in large herbivores is tightly related to digestive physiology, and that chewing efficiency as measured by faecal particle size is an integral aspect of this scenario. Copyright © 2014 Elsevier Inc. All rights reserved.
    Comparative Biochemistry and Physiology - Part A Molecular & Integrative Physiology 10/2014; 179C:182-191. DOI:10.1016/j.cbpa.2014.10.006 · 1.97 Impact Factor
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    • "Actually, in experiments, domestic horses usually ingest lower amounts of forages higher in fibre, responding to forage fibre levels in a similar manner as domestic cattle (Meyer et al., 2010). The general assumption that foregut fermentation and a low-intake/high-efficiency strategy and hindgut fermentation and a high-intake/low-efficiency strategy are linked has recently been modified (Clauss et al., 2010a); in particular, if rumination is added to foregut fermentation, the intake constraints associated with foregut fermentation appear to be less severe, and some hindgut fermenters may also adopt a lowintake/high-efficiency strategy (Clauss et al., 2010b; Steuer et al., 2010), which may explain the lacking fit of experimental data with the traditional concept. "
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    ABSTRACT: Equid digestion is often conceptualized as a high-throughput/low-efficiency system, in particular compared with ruminants. It is commonly assumed that ruminants have an advantage when resources are limited; the effect of low food intake on digestive physiology of horses has, however, not been explored to our knowledge. We used four adult ponies [initial body mass (BM) 288 ± 65 kg] in two subsequent trials with grass hay-only diets [in dry matter (DM): hay1, mid-early cut, crude protein (CP) 10.5%, neutral detergent fibre (NDF) 67.6%; hay2, late cut, CP 5.8%, NDF 69.5%], each fed subsequently at four different dry matter intake (DMI) levels: ad libitum and at 75, 55 and 30 g/kg(0.75) /day. We particularly expected digesta mean retention times (MRT) to increase, and hence fibre digestibility to increase, with decreasing DMI. Ponies maintained BM on the first, but lost BM and body condition on DMI55 and DMI30. MRTs were negatively correlated to DMI and ranged (for particles <2 mm) from 23/31 h (hay1/2) on the ad libitum to 38/48 h on DMI30. Digestibilities of DM, nutrients and fibre components decreased from DMI75 to DMI30; apparent digestibilities of organic matter and NDF (hay1/2) dropped from 47/43% and 42/37%, respectively, on the ad libitum DMI to 35/35% and 30/28% on DMI30. Additional differences evident between the two hays included a higher estimated 'true' protein digestibility for hay1 and finer faecal particles on hay2; there were no differences in faecal particle size between intake levels. The results suggest that below a certain food intake threshold, the major digestive constraint is not fermentation time but nutrient supply to gut bacteria. The threshold for such an effect probably varies between feeds and might differ between ruminants and equids.
    J Anim Physiol a Anim Nutr 02/2013; 98(1). DOI:10.1111/jpn.12053 · 1.41 Impact Factor
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    • "Source of % browse in the diet 1 = Müller et al. (2011); 2 = Steuer et al. (2010) "
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    ABSTRACT: Food preferences of the sand gazelle (Gazella marica) from the Mahazat as-Sayd Protected Area in Saudi Arabia were evaluated using focal animal sampling in conjunction with an eco-morphological method examining two parameters of tooth wear, i.e., occlusal relief and cusp shape. Observations of live, free-ranging animals (n = 53) showed that sand gazelles generally consumed more grass (58.4%) than browse (41.6%). However, during the dry season, gazelles spent significantly more time browsing (51.0%) and less time grazing (49.0%) than under wet conditions (browsing: 17.6%; grazing: 82.4%). Thus, consistent with predictions, sand gazelles are intermediate feeders but shift towards browsing when grass is scarce. The mesowear signature of the sand gazelle is consistent with a grazing signal in other ruminants. In other words, the browse component of the diets of live animals was not reflected in the tooth wear. This could have occurred because browse is less abrasive than grass, but more likely because all food types are heavily abrasive in this dusty habitat. We conclude that the sand gazelle population in Mahazat as-Sayd encounters a highly abrasive diet, which has implications for their ability to meet nutritional demands.
    Mammalian Biology - Zeitschrift fur Saugetierkunde 01/2013; 78(1):55-62. DOI:10.1016/j.mambio.2012.04.006 · 1.48 Impact Factor
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