Babe, the sheep-pig, the hero/heroine of the novel (and films) by Dick King-Smith is always a family favourite. Babe's sheep-herding abilities are based in part on the revelation that there is a secret code among sheep 'Bah Ram Ewe, sheep be true'. As a user of this code, Babe earns a perfect sheep-herding round at the sheepdog trials; to be congratulated by Farmer Hoggett "That'll do Pig. That'll do" and satirised by Peter Griffin, everyone's favourite Family Guy.
Why oh why is he talking about Babe and sheep I thought I heard you ask? The reason is a new piece of research which suggests that even lambs can be picky eaters, and when fed monotonous diets, lambs become more stressed than lambs fed a diverse diet which is also reflected in their physiology and open-field behaviour.
The paper is this one by Villalba and colleagues* published in the journal Physiology & Behaviour. I appreciate that this might be pushing the boundaries of what this blog was originally supposed to do but what this and other research suggests is that we might be able to learn something from our wool-bound friends. Stay with me on this.
I will at this point add that I am in no way suggesting any person, any group of people, or any condition is in anyway related to sheep or any other animal. Some people may have heard that 'All cats have Asperger Syndrome' but not from me.
Back to sheep. The Villalba study looked at 3 diets: (i) a monotonous yet suitably nutritious diet, (ii) a diverse diet changing at set periods with various combinations of foods, (iii) a diverse diet similar to group (ii) also including supplementary phytochemicals. The results. When shown a more diverse diet, the monotonous diet sheep group got more stressed than the other groups as demonstrated by increased plasma cortisol levels and changes to rectal temperature when exposed to the open field test. Stress can be a learned response.
Whilst making generalisations from sheep behaviour to human behaviour is fraught with difficulties, I do feel as though there could be something in such research as this. The implication is that early dietary restrictiveness as a 'norm' might invoke a heightened stress response when a greater number of foods is presented to a person. So when a toddler who eats only pizza and chips (link to BBC3 programme 'Fast food baby') is presented with vegetables or fruit not normally included in the diet, the refusal side of things might not just bring about a tantrum but also some learned physiological stress? The flipside to such observations is that reducing the physiological stress response might make for a more varied diet, as per the recent presentation at the BPS conference on carrot not stick to get children to eat new foods.
Studying mammals like sheep perhaps removes some of the various social and cultural 'baggage' which would accompany similar human research. That and the fact that most human volunteers probably would not like their rectal temperature taken for any kind of experimental study; at least not without some significant reward. I will perhaps return to our mammalian friends at later points in this blog and how, as models of humans, they may offer some special insights into our very human behaviours e.g. autistic mice**?
* Villalba JJ.et al. Relationships between early experience to dietary diversity, acceptance of novel flavors, and open field behavior in sheep. Physiology & Behaviour. August 2011.
** Penagarikano O. et al. Absence of CNTNAP2 leads to epilepsy, neuronal migration abnormalities, and core autism-related deficits. Cell. September 2011.