ABILITY OF LAMBS TO LEARN WITH A DELAY BETWEEN FOOD INGESTION AND CONSEQUENCES GIVEN MEALS CONTAINING NOVEL AND FAMILIAR FOODS

We studied: (1) whether lambs could learn to avoid a novel food given delays of up to 8 h between food ingestion and gastrointestinal illness (long-delay study); (2) how gastrointestinal illness affected the selection of several foods differing in familiarity to lambs (mixed-meal study). Gastrointestinal illness was induced by administering encapsulated lithium chloride (LiCl; 160 mg kg-1 body weight) to lambs using a balling gun. In the long-delay study, lambs were offered a novel food for 5 min. If they consumed 10 g or more of the food, LiCl was administered 0,2,4,6, or 8 h later. Intake of the novel food was measured in 5 min trials for the next 3 days. When the delay between food ingestion and the administration of LiCl was 2 or 4 h, the lambs reduced their intake of the novel food after a single dose of LiCl. The lambs also reduced their intake of the novel food when the delay between food ingestion and the administration of LiCl was 6 or 8 h. However, LiCl was administered twice before the lambs reduced their intake of the novel food; they were also given a stronger dose (320 mg kg-1 body weight) of LiCl on Day 2 than on Day 1. Thus, repeated exposures, greater gastrointestinal distress, or both may be required before lambs reduce their intake of a novel food given delays of 6 h or more. For the mixed-meal study, we used five foods; lambs had eaten two of the foods since weaning, two of the foods for 25 days prior to the onset of the trials, and one food was novel. When lambs were offered the novel food for 5 min followed by the four familiar foods for 20 min, and then given LiCl, they refused to eat the novel food for the next 3 days. Some of the lambs also reduced their intake of the foods they had eaten for 25 days. The lambs did not decrease their intake of the foods they had eaten since weaning.