The digestive performance of mammalian herbivores: why big may not be that much better

1. A traditional approach to the nutritional ecology of herbivores is that larger animals can tolerate a diet of lesser quality due to a higher digestive efficiency bestowed on them by comparatively long ingesta retention times and lower relative energy requirements. 2. There are important physiological disadvantages that larger animals must compensate for, namely a lower gut surface : gut volume ratio, larger ingesta particle size and greater losses of faecal bacterial material due to more fermentation. Compensating adaptations could include an increased surface enlargement in larger animals, increased absorption rates per unit of gut surface, and increased gut motility to enhance mixing of ingesta. 3. A lower surface : volume ratio, particularly in sacciform forestomach structures, could be a reason for the fact that methane production is of significant scope mainly in large herbivores and not in small herbivores with comparably long retention times; in the latter, the substrate for methanogenesis – the volatile fatty acids – could be absorbed faster due to a more favourable gut surface : volume ratio. 4. Existing data suggest that in herbivores, an increase in fibre digestibility is not necessarily accompanied by an increase in overall apparent dry matter digestibility. This indicates a comparative decrease of the apparent digestibility of non-fibre material, either due to a lesser utilization of non-fibre substrate or an increased loss of endogenous/bacterial substance. Quantitative research on these mechanisms is warranted in order to evaluate whether an increase in body size represents a net increase of digestive efficiency or just a shift of digestive focus

The ethicality of using fear for social advertising

While a substantial body of literature has examined the effect of fear appeals in advertising, few, if any, studies have looked into the ethicality of using such threatening messages, particularly for socially desirable outcomes. In this paper, a review of the different theories of ethics leads to the development of an empirical study where the effects of using both physically and socially threatening messages to encourage juveniles to develop anti-smoking behavioural intentions were tested. Using the data collected from a convenience sample of about 250 undergraduates from the University of Adelaide, the results show that fear appeals may indeed be perceived as unethical, even when used for socially desirable purposes. Moreover, social threats were perceived as more unethical and generated less fear than physical threat, suggesting that their use may be counter productive with this type of population. Finally, ethicality did not appear to relate necessarily to change in behavioural intentions. Damien Arthur & Pascale Queste