Links between ruminants’ food preference and their welfare

Abstract

Nutrition is an important aspect of welfare, and in most recommendations for the welfare of animals adequate nutrition is a primary requirement. However, in intensive livestock production systems the decision for adequate nutrition is made based on traditional paradigms of feeding monotonous rations or plant monocultures, frequently with excesses or imbalances of nutrients relative to the individuals' physiology, which can compromise welfare. Individual ruminants can better meet their needs for nutrients and regulate their intake of secondary compounds when offered a variety of foods than when constrained to a single food, even if the food is nutritionally balanced. The concept of food variety is central because monotonous flavors and feeds and excess nutrients all cause animals to satiate, which in turn causes animals to eat a variety of foods. When offered a variety of foods, satiety for single foods stimulates the selection of a diverse diet and thus food intake, but when restricted to a monotonous diet satiety is aversive and limits food intake. Moreover, if a monotonous diet is aversive to animals then this could be stressful, even if monotony implies consuming a balanced diet. A diverse diet may also increase resistance to disease in ruminants, by allowing consumption of small amounts of compounds with antimicrobial/antiparasitic effects and immunity-enhancing properties. Herbivores also experience the benefits of ingesting compounds with medicinal (i.e. antiparasitic) benefits and they learn to prefer foods containing such compounds as their preferences are associatively conditioned by the food's homeostatic utility to the body. Such learned patterns of behavior begin in utero and feeding experiences early in life cause changes -neurological, morphological and physiological -in animals, which influence on their subsequent behavior and welfare. Such experiences with the environment enable animals to adapt to local diets and stressors and reduce the levels of fear. Finally, feeding behavior in farm animals could be an aid in the early detection and mitigation of pain or sickness, and as such become an important tool in the identification of welfare and health of animals before the appearance of clinical signs. Management strategies in ruminant production systems could benefit by allowing animals to manifest their feeding preferences, thereby acknowledging the animals' role as active players in feeding systems, instead of regarding them as passive entities that just respond to prescriptions and formulations.

Feeding behaviour of sheep fed lucerne v. grass hays with controlled post-ingestive consequences

“…Recently, introduction of straw in the rumen (Baumont et al, 2007) or distension with a balloon (Villalba et al, 2009a and2009b) were used to demonstrate that rumen fill is perceived as a negative post-ingestive signal, leading to a decreased preference for the associated forage. We could thus expect the choice of grass hay to be enhanced when it is associated with intraruminal administration of lucerne hay, and conversely the choice of lucerne hay to be decreased when associated with introduction of grass hay, due to differences in fill effect between these two hays.…”

“…This motivation for diversity may be explained by the 'satiety hypothesis' (Provenza et al, 2007;Villalba et al, 2009a and2009b), which suggests that animals acquired transient aversions for a food just eaten as a result of sensory input and post-ingestive feedbacks (nutrients and toxins) interacting along concentration gradients. This transient change in food palatability caused animal to search for a different food and then to eat a diverse diet.…”

Intake pattern and nutrient supply of lactating sheep selecting dried forage from woody plants and straw offered in binary or multiple choice

“…Ginane et al (2002) reported a higher daily DM intake when a choice among two hays of different or similar quality was offered than when one of these hay types was offered alone and explained this by an increased motivation to eat when a diverse offer is available. Even though high quality feeds are preferred by the animals in a choice situation, feeds with lower quality might help to motivate intake simply by increasing the diversity on offer (Ginane et al, 2002), because monotonous diets might lead earlier to a sensory-specific satiety (Rolls, 1986) thus decreasing the motivation to eat due to the lack of feed alternatives (Villalba et al, 2010). When testing different Mediterranean woody forages offered for 6 h/d by varying the number of feeds on offer between each 5-day period, intake increased or decreased along with the number of feeds (Rogosic et al, 2006(Rogosic et al, , 2007 which was explained by the changing biochemical diversity.…”

Why are dairy cows not able to cope with the subacute ruminal acidosis?

“…The feed, which provides chemicals required by an animal at a certain point in space and time, will be more preferred than other feeds. In contrast, if a feed contains compounds which cause negative effects to the organism or the ones which are not needed in that particular point (e.g., excess of nutrients), the preference for the feed will decrease (Villalba et al 2010b). On this basis, ruminants preferentially ingest feeds high in nutrients (Villalba and Provenza 1997) and low in toxins (Provenza et al 1990), but they avoid specific nutrients when needs are met (Villalba and Provenza 1999), and eat toxins when they provide desirable medicinal (e.g., antiparasitic) effects (Villalba et al 2010a).…”