title: Preference for flavoured foods by lambs conditioned with intraruminal administration of nitrogen.
abstract: We suggested that food preference depends on the interplay between flavour and post-ingestive effects, and we predicted that protein-restricted lambs would acquire preferences for foods paired with supplemental sources of N, including urea (Expts 1 and 2), casein (Expt 3), and gluten (Expt 4). In each experiment, twenty lambs, in two groups of ten, were conditioned as follows: on odd-numbered days, lambs in group 1 received wheat straw (Expts 1, 3, and 4) or ground barley (Expt 2) flavoured with a distinctive flavour, and lambs in group 2 received the same 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 conditioning period of 8 d, lambs were given a two-choice test to determine preference for flavours paired with N. In Expts 1 and 2, lambs preferred the flavours conditioned with urea at lower doses (0.12 g N/d in 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 associated with the lowest doses of casein or gluten (0.23 g N/d), but they preferred the flavours paired with casein or gluten at higher doses (0.46 and 0.69 g N/d). After conditioning, N administrations were suspended and lambs in Expts 3 and 4 were offered a choice of the two flavours at weekly intervals for 2 weeks (extinction); preferences persisted during extinction. Collectively, these results suggest that the post-ingestive effects of N in different forms and concentrations influenced the development of food preferences by lambs.
authors.affiliation: Department of Rangeland Resources, Utah State University, Logan 84332-5230, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Villalba
authors.forename: F D
authors.initials: FD
authors.lastname: Provenza
mesh_terms: D000818:Animals; D002364:Caseins / Q000008:administration & dosage; D005260:Female; D005421:Flavoring Agents / Q000008:administration & dosage; D005518:Food Preferences / Q000502:physiology*; D005983:Glutens / Q000008:administration & dosage; D006863:Hydrogen-Ion Concentration; D008297:Male; D009584:Nitrogen / Q000008:administration & dosage* / Q000378:metabolism; D011488:Protein Deficiency / Q000378:metabolism*; D012417:Rumen / Q000378:metabolism*; D012756:Sheep / Q000378:metabolism*; D013649:Taste; D014508:Urea / Q000008:administration & dosage
chemical_list: D002364:Caseins; D005421:Flavoring Agents; D005983:Glutens; D014508:Urea; D009584:Nitrogen