Ž .
and pomace was preferred to pomace–starch during day 9 to 15 P - 0.05 . This pattern quickly reversed — pomace–starch became preferred to pomace — when the foods were offered for 8
Ž .
hrday for the next 6 days P - 0.001 . These findings suggest that energy deprivation and the amount of food ingested both affected how quickly lambs discriminated between foods that
differed in energy, and that lambs needed to eat a threshold amount of an energy-rich novel food before they acquired a preference for that food. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Preferences; Starch; Energy; Supplementation; Experience; Lambs
1. Introduction
Energy supplementation can increase or decrease forage intake, depending on the Ž
kind and amount of supplement consumed and the availability of nitrogen reviewed by .
Ž Caton and Dhuyvetter, 1997 . Low levels of grain supplementation Henning et al.,
. Ž
. 1980 , or low doses of starch infused into the rumen Villalba and Provenza, 1997a ,
increase roughage intake by sheep. Supplementation with energy increases byproducts of Ž
. fermentation like volatile fatty acids VFA , which at low doses condition preferences in
Ž .
sheep Villalba and Provenza, 1996, 1997b . Likewise, sheep prefer poor-quality foods, or non-nutritive flavors in solutions, associated with intraruminal infusions of glucose
Ž .
Ž Burritt and Provenza, 1992; Ralphs et al., 1995 or starch Villalba and Provenza,
. 1997a, 1999 .
Given that byproducts of energy fermentation condition preferences, it is conceivable that ruminants may acquire preferences for poor-quality foods like straw, if straw
ingestion coincides with increased VFA production due to eating an energy-rich supplement just prior to eating the straw. If the effects of VFA from grain supplementa-
tion condition preferences for poor-quality foods, strategic supplementation could en- hance preference for plant species of lesser nutritional quality. On the other hand,
ruminants may quickly discriminate the flavor-post-ingestive effects of the supplement from the poor-quality food, in which case they would not acquire a preference for the
poor-quality food.
Our objective was to better understand how lambs discriminate among novel foods based on flavor and post-ingestive effects, and to determine if energy supplementation
affected the preferences of lambs for a poorly nutritious food. We first determined how temporal order of food ingestion and post-ingestive feedback affected preference when
Ž .
lambs were fed a poorly nutritious food straw immediately after eating an energy-rich Ž
. food milo , and when lambs were fed straw after an infusion of milo into the rumen.
We then determined how lambs discriminated which of two novel foods was highest in energy.
2. Materials and methods
