The role of food sensory characteristics in the feeding behaviour of domestic ruminants

Abstract

When domestic ruminants are faced with food diversity, they can use pre-ingestive information (food sensory characteristics perceived by the animal before swallowing the food) and post-ingestive information (digestive and metabolic consequences experienced by the animal after swallowing the food) to evaluate the food and select a suitable diet. Pre- and post-ingestive information are associated in food learning processes, allowing the animal to avoid food that induces negative consequences while selecting those inducing positive consequences. Post-ingestive information is considered as the main force that influences feeding behaviour whereas food sensory characteristics are only used to discriminate between different foods and to be associated with post-ingestive information in learning processes. Food sensory characteristics can however play other roles. First, some sensory characteristics also possess a hedonic value which influences ruminants' intake, preferences and food learning independently of any immediate post-ingestive consequences. Second, some of these food sensory characteristics become an indicator of post-ingestive consequences after their initial hedonic value has acquired a positive or a negative value via previous individual food learning or evolutionary processes. Thus they represent cues that could help ruminants to anticipate the post-ingestive consequences of a food and to improve their learning efficiency, especially in complex environments. This review then suggests that food sensory characteristics could be of importance to provide pleasure to animals, increase palatability of a food, and help them learn in complex feeding situations which could improve animal welfare and productivity.