Use of Unpalatable Forages by Ruminants: The Influence of Experience with the Biophysical and Social Environment

SIMPLE SUMMARY: Unpalatable forages, due to either low nutrient content or the presence of toxic compounds, are widespread and represent a challenge for ruminant nutrition, health, and welfare. If we find ways to encourage consumption of unpalatable forages, they could provide at least part of the nutrient requirements of ruminants. Our objective was to synthesize the role of diverse environmental experiences on the use of unpalatable forages by ruminants. Experimental evidence shows that experience can alter both morpho-physiological and psychological (learning) mechanisms to better cope with unpalatable forages, particularly early in life when body functions are more amenable to change. Furthermore, experiential learning provides flexibility in diet selection, which is critical in changing foraging environments. By understanding and applying behavioural principles, it is possible to better devise management plans that optimize the nutrition, health, and welfare of herbivores grazing unpalatable forages throughout their life. In addition, a more uniform use of resources can be achieved from the landscape level down to the individual plant, with consequent benefits to ecosystem integrity and stability. ABSTRACT: Unpalatable forage resources (low nutrient density, potentially toxic metabolites) are widespread and represent a challenge for ruminant nutrition, health, and welfare. Our objective was to synthesize the role of biophysical and social experience on the use of unpalatable forages by ruminants, and highlight derived behavioural solutions for the well-being of soils, plants, and animals. Environmental experiences early in life modulate gene expression and promote learning, which alters morpho-physiological and psychological mechanisms that modify behavioural responses and change food and habitat selection. In this process, ruminants can become better adapted to the habitat where they are reared. Moreover, experiential learning provides flexibility in diet selection, which is critical for changing foraging environments. Learned associations between unpalatable and palatable foods, if ingested in appropriate amounts, sequence, and close temporal association, induce the development of preference for the former type of food. In this way, a more uniform use of resources can be achieved from the landscape level down to the individual plant, with the associated benefits to ecosystem integrity and stability. Ruminants can also learn the medicinal benefits of ingesting foods with toxins (e.g., condensed tannins and saponins with antiparasitic properties). This knowledge on behavioural processes can be translated into behavioural applications that provide low-cost solutions to many challenges that producers face in managing sustainable livestock production systems.