PREFERENCE FOR FLAVORED FOODS BY LAMBS CONDITIONED WITH INTRARUMINAL ADMINISTRATION OF NITROGEN

We suggested that food preference depends on the interplay between fla vour and post-ingestive effects, and we predicted that protein-restric ted lambs would acquire preferences for foods paired with supplemental sources of N, including urea (Expts 1 and 2), casein (Expt 3), and gl uten (Expt 4). In each experiment, twenty lambs, in two groups of ten, were conditioned as follows: on odd-numbered days, lambs in group 1 r eceived wheat straw (Expts 1, 3, and 4) or ground barley (Expt 2) flav oured with a distinctive flavour, and lambs in group 2 received the sa me food but with a different flavour. On even-numbered days, flavours were switched and lambs received capsules containing different amounts of urea (ranging from 0.12 to 0.92 g N/d), casein (ranging from 0.23 to 0.69 g N/d), or gluten (ranging from 0.23 to 0.69 g N/d). After con ditioning periods of 8 d, lambs were given a two choice test to determ ine preference for flavours paired with N. In Expts 1 and 2, lambs pre ferred the flavours conditioned with urea at Lower doses (0.12 g N/d i n Expt 1, 0.23 and 0.46 g N/d in Expt 2), but they avoided the flavour associated with urea at the highest dose (0.23 g N/d in Expt 1 and 0. 92 g N/d in Expt 2). In Expts 3 and 4, lambs avoided the flavours asso ciated with the lowest doses of casein or gluten (0.23 g N/d), but the y preferred the flavours paired with casein or gluten at higher doses (0.46 and 0.69 g N/d). After conditioning, N administrations were susp ended and lambs in Expts 3 and 4 were offered a choice of the two flav ours at weekly intervals for 2 weeks (extinction); preferences persist ed during extinction. Collectively, these results suggest that the pos tingestive effects of N in different forms and concentrations influenc ed the development of food preferences by lambs.