Discriminating among Novel Foods: Effects of Energy Provision on Preferences of Lambs for Poor-Quality Foods
Applied Animal Behaviour Science
Villalba, J. and Provenza, F. (2000). Discriminating among novel foods: effects of energy provision on preferences of lambs for poor-quality foods. Applied Animal Behaviour Science, 66(1-2), 87-106. doi:10.1016/S0168-1591(99)00066-0
Our objective was to better understand how lambs discriminate among novel foods based on flavor and post-ingestive effects. We first determined how temporal sequence of food ingestion and post-ingestive feedback affected preference when lambs were fed flavored wheat straw (a poorly nutritious novel food) immediately after eating milo grain (an energy-rich novel food), or after milo was infused in the rumen. Lambs did not acquire a preference for flavored straw when they were fed straw immediately after eating milo (P>.10), evidently because they quickly discriminated the flavor-feedback effects of milo from straw. However, lambs infused with milo prior to eating straw in one flavor or another preferred the flavored straw eaten after the milo infusions (P<0.001), and they preferred milo>flavored straw eaten after milo infusions>flavored straw eaten without milo infusions (P<0.001). Thus, when the flavor cue (milo) was removed, lambs did not discriminate milo from straw to as great a degree as when they first ate milo and then ate straw. We next attempted to better understand how lambs quickly discriminated between novel foods — grape pomace–starch (70–30%) and grape pomace–cellulose (70–30%) — that differ in digestible energy content. Lambs preferred pomace–starch from first exposure (P<0.001), and we hypothesized that they generalized a preference from eating familiar foods like barley and milo that are about 80% starch to the novel grape pomace–starch mixture. To test this hypothesis, we gave lambs a toxin (LiCl) dose after they ate milo, and then measured their preference for pomace–starch. Intake of pomace–starch was lower in the Milo–LiCl group than in controls that received only LiCl (P<0.001), which is consistent with the hypothesis that lambs generalized a preference from familiar foods (barley and milo) to a novel food (pomace–starch). Finally, we determined how duration and amount of exposure to two novel foods — grape pomace–starch (70–30) and grape pomace (100) — influenced preference. When both foods were offered for only 20 min/day, intake of pomace and pomace–starch did not differ on day 1 to 8, 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 h/day 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.