INRA, UMR1213 Herbivores, Saint-Genès-Champanelle, France.
Animal. 2013 May;7(5):806-13. doi: 10.1017/S1751731112002145. Epub 2012 Dec 6.
When domestic ruminants are faced with food diversity, they can use pre-ingestive information (i.e. food sensory characteristics perceived by the animal before swallowing the food) and post-ingestive information (i.e. digestive and metabolic consequences, experienced by the animal after swallowing the food) to evaluate the food and make decisions to select a suitable diet. The concept of palatability is essential to understand how pre- and post-ingestive information are interrelated. It refers to the hedonic value of the food without any immediate effect of post-ingestive consequences and environmental factors, but with the influence of individual characteristics, such as animal's genetic background, internal state and previous experiences. In the literature, the post-ingestive consequences are commonly considered as the main force that influences feeding behaviour whereas food sensory characteristics are only used as discriminatory agents. This discriminatory role is indeed important for animals to be aware of their feeding environment, and ruminants are able to use their different senses either singly or in combination to discriminate between different foods. However, numerous studies on ruminants' feeding behaviour demonstrate that the role of food sensory characteristics has been underestimated or simplified; they could play at least two 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. Further, diversity of food sensory characteristics has a hedonic value, as animals prefer an absence of monotony in food sensory characteristics at similar 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. These food sensory characteristics thus 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, to increase palatability of a food and to help them learn in complex feeding situations which could improve animal welfare and productivity.
当家养反刍动物面临食物多样性时，它们可以利用摄食前信息（即动物在吞咽食物之前通过感官感知到的食物特征）和摄食后信息（即动物在吞咽食物后经历的消化和代谢后果）来评估食物并做出选择合适饮食的决策。适口性的概念对于理解摄食前和摄食后信息是如何相互关联的至关重要。它是指食物的享乐价值，不受摄食后后果和环境因素的直接影响，但受到个体特征的影响，如动物的遗传背景、内部状态和先前的经验。在文献中，通常认为摄食后后果是影响采食行为的主要因素，而食物感官特征仅用作鉴别剂。这种鉴别作用对于动物意识到其采食环境确实很重要，反刍动物能够单独或组合使用它们的不同感官来区分不同的食物。然而，大量关于反刍动物采食行为的研究表明，食物感官特征的作用被低估或简化了；它们至少可以发挥另外两个作用。首先，一些感官特征本身也具有享乐价值，这种价值可以独立于任何直接的摄食后后果影响反刍动物的采食量、偏好和食物学习。此外，食物感官特征的多样性具有享乐价值，因为动物在相似的摄食后后果下更喜欢食物感官特征的多样性而不是单调性。其次，一些食物感官特征在通过先前的个体食物学习或进化过程获得积极或消极的初始享乐价值后，成为摄食后后果的指示物。这些食物感官特征因此代表了可以帮助反刍动物预测食物摄食后后果并提高其学习效率的线索，尤其是在复杂环境中。因此，本综述认为，食物感官特征对于提供动物愉悦感、增加食物的适口性以及帮助它们在复杂的采食情况下学习很重要，这可以提高动物福利和生产力。
