FOOD PREFERENCE AND ACCEPTANCE OF NOVEL FOODS BY LAMBS DEPEND ON THE COMPOSITION OF THE BASAL DIET

Ruminants eat a variety of foods, varying in toxins and nutrients, but no hypotheses adequately explain this behavior. We offer an explanati on, one which encompasses avoidance of toxins and acquisition of nutri ents. A key concept in this hypothesis is aversion, the decrease in pr eference for food just eaten as a result of sensory input (taste, odor , texture, i.e., a food's flavor) and postingestive effects (of toxins and nutrients on chemo-, osmo-, and mechano-receptors) unique to each food. On the basis of this hypothesis, we predicted lambs would prefe r familiar and novel foods that complemented the macro-nutrient compos ition of their basal diet. To assess the validity of this prediction, we fed 10 lambs in each of three treatments different levels of ground barley (high in energy) and alfalfa (high in protein) as a basal diet . We then offered them daily a meal of three ground foods differing in proportions of barley and alfalfa (familiar foods) or wheat and rabbi t pellets (novel foods). We found that lambs fed a basal diet high in energy (barley) preferred food lower in energy and higher in protein ( alfalfa); those fed a diet high in alfalfa preferred food high in barl ey (P < .01). In addition, the higher the barley or alfalfa content of the basal diet, the greater the acceptance of novel foods high in alf alfa (i.e., rabbit pellets) or grain (i.e., wheat), respectively (P < .01). All lambs preferred foods high in wheat to rabbit pellets or alf alfa (P < 0.01), evidently because wheat is high in energy and it diff ers in flavor from barley, which was eaten repeatedly as part of the b asal diet. On the basis of these results, we contend that lambs prefer red familiar and novel foods that complemented the flavors and macro-n utrient contents of their basal diet.