Originally published at: Steuer, P; Südekum, K H; Müller, D W H; Franz, R; Kaandorp, J; Hummel, J (2011). Is there an influence of body mass on digesta mean retention time in herbivores? A comparative study on ungulates. Comparative Biochemistry and Physiology -Part A: Molecular and Integrative Physiology, Is there an influence of body mass on digesta mean retention time in herbivores? A comparative study on ungulates AbstractThe relation between body mass (BM) and digesta mean retention time (MRT) in herbivores was the focus of several studies in recent years. It was assumed that MRT scaled with BM0.25 based on the isometric scaling of gut capacity (BM1.0) and allometric scaling of energy intake (BM0.75). Literature studies that tested this hypothesis produced conflicting results, arriving sometimes at higher or lower exponents than the postulated 0.25. This study was conducted with 8 ruminants (n=2-6 per species) and 6 hindgut fermenting species/breeds (n=2-6, warthog n=1) with a BM range of 60-4000 kg. All animals received a ration of 100% grass hay with ad libitum access. Dry matter intake was measured and the MRT was estimated by the use of a solute and a particle (1-2 mm) marker. No significant scaling of MRTparticle with BM was observed for all herbivores (32 BM0.04, p=0.518) and hindgut fermenters (32 BM0.00, p=1.00).The scaling exponent for ruminants only showed a tendency towards significance (29 BM0.12, p=0.071). Ruminants on average had an MRTparticle 1.61-fold longer than hindgut fermenters. Whereas an exponent of 0.25 is reasonable from theoretical considerations, much lower exponents were found in this and other studies. The energetic benefit of increasing MRT is by no means continuous, since the energy released from a given food unit via digestion decreases over time. The low and non-significant scaling factors for both digestion types suggest that in ungulates, MRT is less influenced by BM (maximal allometric exponent≤0.1) than often reported. 1Is there an influence of body mass on digesta mean retention time in ). Literature studies that tested this hypothesis produced conflicting results, arriving 17 sometimes at higher or lower exponents than the postulated 0.25. This study was conducted 18 with 8 ruminants (n = 2-6 per species) and 6 hindgut fermenting species/breeds (n = 2-6, 19 warthog n = 1) with a BM range of 60-4000 kg. All animals received a ration of 100% grass 20 hay with ad libitum access. Dry matter intake was measured and the MRT was estimated by 21 the use of a solute and a particle (1-2 mm) marker. No significant scaling of MRT particle with 22BM was observed for all herbivores (32 BM , p = 0.071). Ruminants on average had a MRT particle 1.61-fold longer 25 than hindgut fermenters. Whereas an exponent of 0.25 is reasonable from theoretical 26 considerations, much lower exponents were found in this and other studies. The energetic 27 benefit of increasing MRT is by no means continuous, since the energy released from a given 28 food unit via digestion decreases over time. The low ...

The ability to recognize individuals is an important aspect of social interactions, but it can also be useful to avoid repeated matings with the same individual. The Coolidge effect is the progressive decline in a male's propensity to mate with the same female combined with a heightened sexual interest in new females. Although males that recognize previous partners and show a preference for novel females should have a selective advantage as they can distribute sperm evenly among the females they encounter, there are few invertebrate examples of the Coolidge effect. Here we present evidence for this effect in the burying beetle Nicrophorus vespilloides and examine the mechanism underlying the discrimination between familiar and novel mates. Burying beetles feed and reproduce on vertebrate carcasses, where they regularly encounter conspecifics. Males showed greater sexual interest in novel females (virgin or mated) than in females they had inseminated before. The application of identical cuticular extracts allowed us to experimentally create females with similar odours, and male responses to such females demonstrated that they use female cuticular patterns for discrimination. The chemical analysis of the cuticular profile revealed greater interindividual variation in female than in male cuticular patterns, which might be due to greater selection on females to signal their individual identity.

Allometric equations are often used to extrapolate traits in animals for which only body mass estimates are known, such as dinosaurs. One important decision can be whether these equations should be based on mammal, bird or reptile data. To address whether this choice will have a relevant influence on reconstructions, we compared allometric equations for birds and mammals from the literature to those for reptiles derived from both published and hitherto unpublished data. Organs studied included the heart, kidneys, liver and gut, as well as gut contents. While the available data indicate that gut content mass does not differ between the clades, the organ masses for reptiles are generally lower than those for mammals and birds. In particular, gut tissue mass is significantly lower in reptiles. When applying the results in the reconstruction of a sauropod dinosaur, the estimated volume of the coelomic cavity greatly exceeds the estimated volume of the combined organ masses, irrespective of the allometric equation used. Therefore, substantial deviation of sauropod organ allometry from that of the extant vertebrates can be allowed conceptually. Extrapolations of retention times from estimated gut contents mass and food intake do not suggest digestive constraints on sauropod dinosaur body size.

, J; Clauss, M (2011). Methane output of rabbits (Oryctolagus cuniculus) and guinea pigs (Cavia porcellus) fed a hay-only diet: Implications for the scaling of methane production with body mass in non-ruminant mammalian herbivores. It is assumed that small herbivores produce negligible amounts of methane, but it is unclear whether this is a physiological peculiarity, or simply a scaling effect. A respiratory chamber experiment was conducted with six rabbits (Oryctolagus cuniculus, 1.57 ± 0.31 kg body mass) and six guinea pigs (Cavia porcellus, 0.79 ± 0.07 kg) offered grass hay ad libitum.Daily dry matter (DM) intake and DM digestibility were 50 ± 6 g kg ) and indicates linear scaling. Because feed intake typically scales to BM 0.75 , linear scaling of methane output translates into increasing energetic losses at increasing BM. Accordingly, the data collection indicates that an increasing proportion of ingested gross energy is lost because relative methane production increases with BM. Different from ruminants, such losses (1-2% of gross energy) appear too small in non-ruminant herbivores to represent a physiologic constraint on body size. Nevertheless, this relationship may represent a physiological disadvantage with increasing herbivore body size.--

Summary A colonic separation mechanism (CSM) is the prerequisite for the digestive strategy of coprophagy. Two different CSM are known in small herbivores, the ‘wash‐back’ CSM of lagomorphs and the ‘mucous‐trap’ CSM of rodents. Differences between these groups in their digestive pattern when fed exclusively hay were investigated in six rabbits (Oryctolagus cuniculus) and six guinea pigs (Cavia porcellus). Intake, digestibility (by total faecal collection), solute and particle mean retention times (MRT, using Co‐EDTA and Cr‐mordanted fibres) were measured. Rabbits selected less fibrous parts of the hay than guinea pigs, leaving orts with higher content of neutral detergent fibre [NDF; 721 ± 21 vs. 642 ± 31 g/kg dry matter (DM) in guinea pigs]. They also expressed a lower NDF digestibility (0.44 ± 0.10 vs. 0.55 ± 0.05 of total), a similar particle MRT (15 ± 3 vs. 18 ± 6 h), a longer solute MRT (51 ± 9 vs. 16 ± 4 h), and a lower calculated dry matter gut fill (19.6 ± 4.7 vs. 29.7 ± 4.1 g DM/kg body mass) than guinea pigs (p < 0.05 for each variable). These results support the assumption that the ‘wash‐back’ CSM, exhibited in the rabbits, is more efficient in extracting bacterial matter from the colonic digesta plug than the ‘mucous‐trap’ CSM found in the guinea pigs. Related to metabolic body mass, rabbits therefore need a less capacious colon for their CSM where a more efficient bacteria wash‐out is reflected in the lower fibre digestibility. A lighter digestive tract could contribute to a peculiarity of lagomorphs: their ability to run faster than other similar‐sized mammals.