Not all sheep prefer clover: diet selection revisited

2010

Animal

Understanding what determines feeding behaviour in herbivores is essential to optimise the use of forages in breeding systems. Herbivores can evaluate foods by associative learning of their pre-ingestive characteristics (taste, odour, etc.) and their postingestive consequences. Post-ingestive consequences are acknowledged as influencing intake and food choices, but the role of pre-ingestive characteristics is still being debated. Our experiment was designed to test their separate effects on daily dry matter intake (DMI), intake patterns and short-term choices in sheep by crossing the nature of the hay orally consumed (o) ad libitum, lucerne (L) or grass (G), with the nature of the hay introduced into the rumen (r), L or G, at a rate of half the total amount of hay received the day before. We applied four treatments, Go/Gr, Go/Lr, Lo/Gr and Lo/Lr, to test the effects of (i) post-ingestive consequences with similar pre-ingestive characteristics (Go/Gr v. Go/Lr; Lo/Gr v. Lo/Lr) and (ii) pre-ingestive characteristics with similar post-ingestive consequences at the end of the feeding period (Go/Lr v. Lo/Gr). Six rumen-fistulated sheep underwent all the treatments over 11-day periods in a latin square design. Eating time was restricted to 6 h/day, intraruminal introductions were performed just before food offer and choice tests were conducted after food removal. For similar pre-ingestive characteristics, DMI increased when L hay was introduced into the rumen rather than G ( P , 0.05), possibly owing to a lower fill effect of L due to its lower NDF content and higher rumen degradability. The increased DMI resulted from longer eating time when G was orally consumed (149 v. 192 min, P , 0.05), whereas it resulted from higher intake rate with L (4.8 v. 6.1 g/min, P , 0.05). For similar post-ingestive consequences at the end of the feeding period (Go/Lr and Lo/Gr), DMI were similar ( P . 0.05). Pre-ingestive characteristics or palatability per se did not therefore influence daily intake, although they influenced eating patterns. Pre-ingestive characteristics also greatly influenced short-term choices in favour of the hay that was not previously consumed, independently of any post-ingestive influence. This study confirms the effects of post-ingestive consequences on daily intake, but demonstrates that these variations are obtained by different behavioural adjustments under the influence of pre-ingestive characteristics. Preference for novelty, regardless of post-ingestive consequences, thus suggests that sheep may seek a diverse diet more for pleasure than for functional purposes, with implications for animal welfare.Keywords: feeding behaviour, intake, sensory characteristics, rumen, sheep ImplicationsBreeding systems tend to increase the proportion of forages in the total diet of ruminants, both for economic gain and in response to social demand for environmental protection and welfare. However, their use remains to be optimised. To do this we need a better understanding of how food characteristics influence feeding beh...

Section: Short-term Choices: Effect Of Recent Dietary Experiencesmentioning

confidence: 87%

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

Favreau

2010

Animal

“…This was true for sheep preferring the flavour presented first within a conditioning period over that presented second (Arsenos et al, 2000), for ewes preferring the opposite species (i.e. white clover or ryegrass) to the one they had previously grazed (Newman et al, 1992;Parsons et al, 1994), and for heifers temporarily increasing their preference for the hay that had not been offered during the previous period (Ginane et al, 2002). The authors suggested that the preference for the 'new' hay could be explained by (i) the animal's need to select a balanced diet that best meets its homeostatic requirements or (ii) the animals' search for rarity for functional purposes, such as maintaining gut flora diversity or (iii) an attractive effect of novelty, considered as a search for diversity.…”

Section: Sensory Characteristics: a Way To Get Pleasurementioning

confidence: 95%

Food sensory characteristics: their unconsidered roles in the feeding behaviour of domestic ruminants

Favreau-Peigné

2013

Animal

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.

“…In the literature, the studies on choices between forages of different quality are relative to only one difference in quality, that is in choice trials between rye-grass and clover [1,21,23] or between vegetative and reproductive swards [6], or when one of the two forages is pelleted [3,18].…”

Section: Introductionmentioning

confidence: 99%

Feeding behaviour and intake of heifers fed on hays of various quality, offered alone or in a choice situation

Lassalas³

et al. 2002

Anim. Res.

-We studied the feeding behaviour of cattle offered unconstrained choices between two hays of either different or similar nutritive values, and linked these choices to their behaviour when the same forages were offered alone. Over successive 10-day periods, six 15-month-old Aubrac heifers received three hays (a leafy one, G, and two late cut ones, C1 and C2, of very similar nutritive value), ad libitum, alternately alone and associated two by two. As expected, the heifers ate more G than C1 or C2 when the hay was offered alone, and preferred G in choice trials. They displayed a similar behaviour towards C1 and C2 when they were given alone, and also when they were independently associated with G (C1 and C2 making up 18% and 17% of the total intake and 21% and 17% of total feeding time, respectively) or when they were offered together (each accounting for nearly 50% of the total intake or feeding time). The choices could be related to the daily intakes of the forages given alone, which could thus be a good predictor of relative daily intakes under choice conditions. Heifers always showed partial choices, which could be seen as the research of the maintenance of optimal ruminal conditions, the result of sampling behaviour and/or the pleasure associated with the diversity of the diet. Their tendency to diversify the diet was also supported by the reaction to the recent diet by temporarily increasing their preference for the hay that had not been offered during the previous nochoice sub-period. Finally, all the choice situations raised the daily dry matter intake, which could be seen as the result of their motivation to eat due to the diversity of the offer. de regain G et deux foins tardifs C1 et C2 de valeurs alimentaires similaires) à volonté, alternativement distribués seuls ou associés deux par deux. Les génisses ont ingéré G en plus grande quantité que C1 ou C2 lorsque les foins étaient distribués seuls et l'ont préféré en situation de choix. Elles ont eu des comportements similaires vis-à-vis de C1 et de C2 distribués seuls, mais également lorsqu'ils étaient offerts avec G (C1 et C2 représentant respectivement 18 % et 17 % des quantités ingérées totales, et 21 % et 17 % du temps d'ingestion) ou lorsqu'ils étaient distribués ensemble (chaque foin représentant environ 50 % des quantités ingérées et du temps d'ingestion). Les choix étaient en accord avec l'ingestibilité des fourrages distribués seuls, qui pourrait donc être un bon critère de prévision des quantités ingérées relatives en situation de choix. Les génisses ont toujours montré des choix mixtes, ce qui peut être interprété comme la recherche d'un maintien de conditions ruminales optimales, le résultat d'un comportement d'échantillonnage et/ou du plaisir associé à un régime diversifié. Leur tendance à diversifier le régime s'est également exprimée lors du passage d'une situation de non choix à une situation de choix, par l'augmentation temporaire de leur préférence pour le foin qui n'avait pas été distribué précédemment. Enfin, la situation de...