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Figure 2 Comparison of the data on blackbuck (Antilope cervicapra) and nilgai (Boselaphus tragocamelus) from this study with literature data. a) The relationship of the mean retention time (MRT) of solute and particle (<2 mm) markers in the reticulorumen (RR) as compared to ‘moose-type’ and ‘cattle-type’ ruminants from Clauss et al. (2010b). Note that both species plo} within the ‘cattle-type’ ruminants. b) The relationship between the intraruminal papillation pattern, expressed as the surface enlargement factor (SEF) in the dorsal rumen as a percentage of the SEF in the ruminal atrium (a larger value represents a more homogenous intraruminal papillation) from Clauss et al. (2009c) and the average selectivity factor (SF, the ratic Of MRT particie tO MRT solute) in the RR (from Hebel et al., 2011). Note that while nilgai plot within the expected range, the SFgp of this study indicates that the papillation value reportec previously might be too high for blackbuck. Evaluation of the values for the blackbucks of this study arrives at an unequivocal result: a SFrr of 3.2 (Table 1), is at the higher end of values measured for grazing ruminants, and clearly above the level typical for browsing ruminants. It resembles, in its magnitude, values previously reported in cattle (Hummel et al., 2005). When comparing the measure- ments of this study to a data collection from typical ‘cattle-type’ and ‘moose-type’ ruminants (Fig. 2a), it is evident that blackbuck and nilgai fall within the range of ‘cattle-type’, but with blackbuck being much more extreme in this respect. Comparing the SFgr to the rumen papillae distribution (Clauss et al., 2009c), a similar pattern emerges, with blackbuck displaying even higher SFr than expected from ruminal papillae distribution, and nilgai close to the expected range (Fig. 2b). The comparison of the two species does not imply a major influence of BM on patterns of retention times of ruminants: A high SFr is a typical trait of cattle, the prime example of a grazing ruminant. The small grazer blackbuck matches the cattle pattern more than the larger in- termediate feeder nilgai (although both can be considered ‘cattle-type’ ruminants based on their retention time pattern). Dry matter intake was 0.47 kg/day for blackbuck and 1.6 kg/day for nilgai, resulting in body mass related intakes on a level of 40 g/kg BM°’°/day for blackbucks and 35 g/kg BM®°/day for nilgai dur- ing the trial (Table 1). Typical digesta marker excretion curves for black- buck and nilgai are given in Fig. 1. No differences were found between the species in MRT GIT and MRTparticeRR, but MRTso1ureRR and in conse- quence also SFrr differed significantly between the two species (Table 1). Hypotheses on consequences of SF rather focus on the rumen reticulum, since the difference in retention times of solutes and particles are largely due to processes in this part of the GIT. Se- lectivity factor values for the total GIT are always lower due to the
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