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

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 post-ingestive 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.     

How does pattern of feeding and rate of nutrient delivery influence conditioned food preferences?

Ruminant herbivores have been shown to learn about food properties by associating food flavours with the food’s post-ingestive consequences. Previous experimentation supporting the conditioned food aversion/preference hypothesis has generally employed very simple diet learning tasks which do not effectively represent the wide range of foods selected within single bouts typical of wild, free-ranging ruminant herbivores. We tested the ability of a ruminant herbivore to associate a food with artificially administered nutrient rewards in a designed experiment where we altered the temporal pattern of encounter with the food as well as the nature (fast or slow reward) of the post-ingestive outcome. Twenty-four goats were offered branches of Sitka spruce (SS) and Norway spruce (NS) for 4 h per day on two days per week for five weeks. The pattern of feeding varied with treatment such that the species on offer changed every hour (short) or every 2 h (long). The energy treatment altered the reward delivered during Sitka consumption so that animals were dosed either with predominantly sugar (rapidly fermented), predominantly starch (slower fermentation rate), or with water (placebo). Preference was measured on the day following each learning day. We expected that goats would find it easier to associate SS with post-ingestive rewards when the duration of encounter was longest, and that associations would be stronger with the most rapidly digested post-ingestive reward. In the event, goats did not alter their consumption of SS in response to the treatments. Our results suggest that at the scale of temporal resolution of encounters with different plant species (1–2 h), and at the different rates of experiencing post-ingestive consequences tested in this experiment, ruminants do not appear to discriminate the nutritive properties of foods predominantly through a post-ingestive feedback mechanism. They must, instead, use a range of cues—including post-ingestive consequences—to assess food properties. An erratum to this article can be found at     

Diet learning through post-ingestive consequences in sheep: the case of starch and casein variously combined in the same foods

Ruminants generally succeed in selecting an appropriate diet relative to their nutrient requirements, and macronutrients such as energy and protein are considered as playing a primary role in their food preferences. Diet learning through post-ingestive consequences, evidenced by many studies that involved situations with simple discrimination tasks, may explain this ability to select a suitable diet. However, in more complex feeding environments where animals are faced with many plants varying both in their energy and protein contents, the extent to which such a mechanism operates is still uncertain. Our objective was to investigate a more complex feeding situation than previously tested and to determine whether lambs were able to associate three forages with both energy-based and protein-based post-ingestive consequences of various intensities. The doses of starch and casein used to elicit these post-ingestive consequences were chosen so that the apparent metabolisable energy and crude protein values of hays were within the range found in plants normally encountered under field conditions. We applied five treatments: EmPm, EhPm, EmPh, EhPh, where medium (m) or high (h) levels of nutrients (E = energy and P = protein) were associated with different hays, and E0N0 where no stimuli were associated. Each animal experienced only three treatments: E0N0-EmPm-EhPm or E0N0-EmPh-EhPh, each one being associated with one hay during conditioning, on the basis of one treatment per day over three consecutive days. Animals then had a choice between the hay associated with E0N0 and one of the two others, successively on the two following days. This procedure was repeated through five 1-week-long periods, and applied to two groups of lambs (n = 12) maintained at feeding levels sufficient for maintenance or for a 150 g/day growth rate. This experiment was complemented by a methodological trial that aimed to estimate the doses of starch and casein eliciting preferences and a post-trial that aimed to evaluate the effect of our treatments on sheep ruminal environment. The methodological trial showed that lambs perceived the stimuli and the doses, and the post-trial showed that treatments affected the ruminal environment. In the main experiment, the lambs preferred the rewarded hays but did not discriminate in their choices the variation of post-ingestive consequences due to energy and protein. This suggests that in situations closer to reality where animals experience many foods varying in nutrient contents, the learning process may be impaired. The lambs do not seem to have strictly relied on it for shaping their diet choices.     

Mechanisms of intake induction of a low-nutritious food in sheep (Ovis aries)

Intake induction refers to the phenomenon by which animals increase consumption of a less-valued meal when followed by a highly-preferred food relative to when followed by no food or by the same less-preferred food. In the Training phase of the present experiment, we assessed the induction effect in sheep using a within-subject design where learning could be tested while controlling for digestive state. Results showed that, once intake reached stability, subjects ate more low-nutritious food (oat hay) when followed than when preceded by a preferred food (soybean meal), supporting the learning hypothesis of induction. The objective of the second, Revaluation, phase of the experiment was to explore the associative mechanism of induction, for which we paired gastrointestinal malaise caused by lithium chloride intoxication with consumption of soybean meal or a control food (wheat bran). Despite subjects partially rejecting soybean meal relative to controls after the aversive conditioning protocol, oat hay consumption seemed unaffected by soybean meal devaluation. We conclude that intake induction in sheep may rely on changes in hedonic properties of the low-nutritious food based on its association with post-ingestive feedback from the preferred food (hedonic hypothesis), but not on an explicit anticipation of the latter (signalling hypothesis).     

Review: Optimizing ruminant conversion of feed protein to human food protein

Ruminant livestock have the ability to produce high-quality human food from feedstuffs of little or no value for humans. Balanced essential amino acid composition of meat and milk from ruminants makes those protein sources valuable adjuncts to human diets. It is anticipated that there will be increasing demand for ruminant proteins in the future. Increasing productivity per animal dilutes out the nutritional and environmental costs of maintenance and rearing dairy animals up to production. A number of nutritional strategies improve production per animal such as ration balancing in smallholder operations and small grain supplements to ruminants fed high-forage diets. Greenhouse gas emission intensity is reduced by increased productivity per animal; recent research has developed at least one effective inhibitor of methane production in the rumen. There is widespread over-feeding of protein to dairy cattle; milk and component yields can be maintained, and sometimes even increased, at lower protein intake. Group feeding dairy cows according to production and feeding diets higher in rumen-undegraded protein can improve milk and protein yield. Supplementing rumen-protected essential amino acids will also improve N efficiency in some cases. Better N utilization reduces urinary N, which is the most environmentally unstable form of excretory N. Employing nutritional models to more accurately meet animal requirements improves nutrient efficiency. Although smallholder enterprises, which are concentrated in tropical and semi-tropical regions of developing countries, are subject to different economic pressures, nutritional biology is similar at all production levels. Rather than milk volume, nutritional strategies should maximize milk component yield, which is proportional to market value as well as food value when milk nutrients are consumed directly by farmers and their families. Moving away from Holsteins toward smaller breeds such as Jerseys, Holstein-Jersey crosses or locally adapted breeds (e.g. Vechur) would also reduce lactose production and improve metabolic, environmental and economic efficiencies. Forages containing condensed tannins or polyphenol oxidase enzymes have reduced rumen protein degradation; ruminants capture this protein more efficiently for meat and milk. Although these forages generally have lower yields and persistence, genetic modification would allow insertion of these traits into more widely cultivated forages. Ruminants will retain their niches because of their ability to produce valuable human food from low value feedstuffs. Employing these emerging strategies will allow improved productive efficiency of ruminants in both developing and developed countries.     

Remembering nutrient quality of sugar in Drosophila

Taste is an early stage in food and drink selection for most animals [1, 2]. Detecting sweetness indicates the presence of sugar and possible caloric content. However, sweet taste can be an unreliable predictor of nutrient value because some sugars cannot be metabolized. In addition, discrete sugars are detected by the same sensory neurons in the mammalian [3] and insect [4, 5] gustatory systems, making it difficult for animals to readily distinguish the identity of different sugars using taste alone [6-8]. Here we used an appetitive memory assay in Drosophila [9-11] to investigate the contribution of palatability and relative nutritional value of sugars to memory formation. We show that palatability and nutrient value both contribute to reinforcement of appetitive memory. Nonnutritious sugars formed less robust memory that could be augmented by supplementing with a tasteless but nutritious substance. Nutrient information is conveyed to the brain within minutes of training, when it can be used to guide expression of a sugar-preference memory. Therefore, flies can rapidly learn to discriminate between sugars using a postingestive reward evaluation system, and they preferentially remember nutritious sugars.     

Learning to forage in a regenerating patchy environment: Can it fail to be optimal?

The behaviour of animals foraging along closed traplines of regenerating patches of food has been simulated using a learning rule that determines when an animal should leave the patch at which it is currently feeding to search for another one. The rule causes the animal to stay at the patch as long as it is feeding faster than it remembers doing. The foraging behaviour of one animal, and of two or more animals together, feeding in traplines containing patches of the same and of differing types has been simulated, and in all cases the foraging behaviour generated by the rule allowed the animals to exploit the food very efficiently. The learning model is also responsible for indirect social interactions among animals sharing the same trapline because the feeding of each animal reduces the availability of food for the others. This causes a population of animals to disperse themselves, on average, among patches of food according to the ideal free distribution. The relationship between the learning model and conventional optimal foraging models is examined and it is shown that it is pointless to try to account for learned behaviour in the context of optimal foraging theory.     

Review: Authentication of grass-fed meat and dairy products from cattle and sheep

Meat and dairy products derived from grassland carry premium values and sensory and nutritional qualities that aroused much interest for authentication methods to guarantee grassland origin claims. This article reviews the current state of knowledge on the authentication of meat and dairy of grassland origin from food analysis in both cattle and sheep. A range of methods alone or combined, involving analysis of elemental or molecular constituents of food product and fingerprinting profiling combined with chemometrics, have been developed and proved useful to differentiate contrasted feeding regimes and authenticate grass-fed meat and dairy. Their robustness and discriminatory reliability in more complex feeding conditions, such as in the case of dietary switches or when grass only makes up part of the animal’s diet, are under active investigation. Our review highlights the possibilities and limitations of these methods, the latter being chiefly posed by variations in the quantity, characteristics and composition of grassland feedstuffs consumed by animals, which are nevertheless inherent to grassland-based production systems, variations in animal responses within and across breeds, and difficulties in detecting the consumption of non-grass feedstuffs by the animal. It also highlights a number of issues for consideration, points of caution and caveats in applying these methods. Scientists agree that much of the research carried out so far has been a ‘proof of concept’ type and that efforts should be made in the future to develop more databases to help gain genericity and robustness.     

Preference of intake of different tree leaves preserved with drying and ensiling by nyala antelope (Tragelaphus angasii)

It is recommended that browse should be an important part of diets for browsing and intermediate feeding type ruminants. However, provision of browse in winter time is problematic for many zoos located in the temperate climate. Drying or freezing of branches are commonly practiced solutions to this problem, but ensiling of tree leaves could also be an attractive option. The aim of this study was to determine the effect of drying and ensiling of different tree leaves on preference of their intake by nyala antelope (Tragelaphus angasii), an intermediate feeding type ruminant. A study was conducted on five nyala fed a standard diet (meadow hay, dehydrated chopped lucerne and limited concentrates) before and during the study. Preference of intake of five feeds was tested: dried maple (A. platanoides), oak (Q. robur), willow (S. alba), and ensiled maple and lime (T. cordata) leaves. Each day two tested feeds were offered to each animal. After 4 h of presentation, feed refusals were weighed and preference ratio for each tested feed and animal was calculated. Then, preferences were ranked using a pairwise comparison chart. Dried maple and oak leaves were preferred more than other leaves whereas ensiled lime leaves were the least preferred. On the other hand, ensiled and dried maple leaves were equally preferred. Results of this study showed that palatability of ensiled tree leaves should not be a concern when feeding nyala, and likely also other browsing or intermediate feeding type ruminants, but palatability of silage may depend on the species of tree.     

Food intake is influenced by sensory sensitivity

Wide availability of highly palatable foods is often blamed for the rising incidence of obesity. As palatability is largely determined by the sensory properties of food, this study investigated how sensitivity to these properties affects how much we eat. Forty females were classified as either high or low in sensory sensitivity based on their scores on a self-report measure of sensory processing (the Adult Sensory Profile), and their intake of chocolate during the experiment was measured. Food intake was significantly higher for high-sensitivity compared to low-sensitivity individuals. Furthermore, individual scores of sensory sensitivity were positively correlated with self-reported emotional eating. These data could indicate that individuals who are more sensitive to the sensory properties of food have a heightened perception of palatability, which, in turn, leads to a greater food intake.     

MAPPING THE EFFECT OF INFORMATION ABOUT ANIMAL WELFARE ON CONSUMER LIKING AND WILLINGNESS TO PAY FOR YOGURT

Preference mapping identified different groups of consumers on the basis of their disconfirmations (occurring when the product is either better or worse than expected) and assimilations (occurring when actual liking [L] moves toward the expectations). The negative disconfirmation of a group of consumers (Group 1) was based on the information about animal welfare (the products were worse than expected because the information about animal welfare induced high expectations), whereas in Group 2 the sensory properties of the products prevailed in orienting consumer disconfirmation (products were worse than expected because the sensory properties of low-fat yogurt were disliked). The map of assimilation showed that consumers from Group 1 had higher assimilation for plain yogurt associated with high welfare standards as a consequence of the high discrepancy between blind and expected L for these products. A similar behavior was observed for Group 2 (higher discrepancy between blind and expected L corresponding to higher assimilation for low-fat yogurt paired with high welfare standards).

PRACTICAL APPLICATIONS

Consumers based their choices both on sensory properties (plain yogurts were preferred to low-fat yogurts) and on information about animal welfare (products associated with high welfare standards were preferred to the others). Preference mapping was able to identify groups of consumers behaving differently, as compared with the general trend, on the basis of their disconfirmations and assimilations.
Consumer willingness to pay reflected the hedonic behavior, thus validating the auction procedure for food liking evaluation purposes and providing a useful tool to obtain information about the real value (i.e., in monetary terms) consumers give to animal welfare.     

Social interaction with non-averse group-mates modifies a learned food aversion in single- and mixed-species groups of tamarins (Saguinus fuscicollis and S. labiatus)

For social species, being a member of a cohesive group and performing activities as a coordinated unit appear to provide a mechanism for the efficient transmission of information about food. Social learning about food palatability was investigated in two captive primates, Saguinus fuscicollis and S. labiatus, which form stable and cohesive mixed-species groups in the wild. We explored whether an induced food aversion toward a preferred food is modified during and after social interaction with non-averse conspecifics or congeners. Sets of intra- and interspecific pairs were presented with two foods, one of which was considered distasteful by one of the pairs (the other was palatable), and their behavior was compared pre-interaction, during interaction, and post-interaction. For the aversely-conditioned individuals of both species, the change in social context corresponded to a change in their preference for the food that they considered unpalatable, regardless of whether they had interacted with a conspecific or congeneric pair, and the change in food preference was maintained post-interaction. In a control condition, in which averse individuals did not have the opportunity to interact with non-averse animals, S. fuscicollis sampled the preferred food, but not as quickly as when given the opportunity to interact. We conclude that the social learning demonstrated here may allow individual tamarins to track environmental change, such as fruit ripening, more efficiently than asocial learning alone, because social learners can more quickly and safely focus on appropriate behavior by sharing up-to-date foraging information. Furthermore, since the behavior of congeners, as well as conspecifics, acts to influence food choice in a more adaptive direction, social learning about food palatability may be an advantage of mixed-species group formation to tamarins of both species.     

Evolutionary adaptations of ruminants and their potential relevance for modern production systems

Comparative physiology applies methods established in domestic animal science to a wider variety of species. This can lead to improved insight into evolutionary adaptations of domestic animals, by putting domestic species into a broader context. Examples include the variety of responses to seasonally fluctuating environments, different adaptations to heat and drought, and in particular adaptations to herbivory and various herbivore niches. Herbivores generally face the challenge that a high food intake compromises digestive efficiency (by reducing ingesta retention time and time available for selective feeding and for food comminution), and a variety of digestive strategies have evolved in response. Ruminants are very successful herbivores. They benefit from potential advantages of a forestomach without being constrained in their food intake as much as other foregut fermenters, because of their peculiar reticuloruminal sorting mechanism that retains food requiring further digestion but clears the forestomach of already digested material; the same mechanism also optimises food comminution. Wild ruminants vary widely in the degree to which their rumen contents 'stratify', with little stratification in 'moose-type' ruminants (which are mostly restricted to a browse niche) and a high degree of stratification into gas, particle and fluid layers in 'cattle-type' ruminants (which are more flexible as intermediate feeders and grazers). Yet all ruminants uniformly achieve efficient selective particle retention, suggesting that functions other than particle retention played an important role in the evolution of stratification-enhancing adaptations. One interesting emerging hypothesis is that the high fluid turnover observed in 'cattle-type' ruminants - which is a prerequisite for stratification - is an adaptation that not only leads to a shift of the sorting mechanism from the reticulum to the whole reticulo-rumen, but also optimises the harvest of microbial protein from the forestomach. Although potential benefits of this adaptation have not been quantified, the evidence for convergent evolution toward stratification suggests that they must be substantial. In modern production systems, the main way in which humans influence the efficiency of energy uptake is by manipulating diet quality. Selective breeding for conversion efficiency has resulted in notable differences between wild and domestic animals. With increased knowledge on the relevance of individual factors, that is fluid throughput through the reticulo-rumen, more specific selection parameters for breeding could be defined to increase productivity of domestic ruminants by continuing certain evolutionary trajectories.     

Exposures to conditioned flavours with different hedonic values induce contrasted behavioural and brain responses in pigs

This study investigated the behavioural and brain responses towards conditioned flavours with different hedonic values in juvenile pigs. Twelve 30-kg pigs were given four three-day conditioning sessions: they received three different flavoured meals paired with intraduodenal (i.d.) infusions of 15% glucose (F(Glu)), lithium chloride (F(LiCl)), or saline (control treatment, F(NaCl)). One and five weeks later, the animals were subjected to three two-choice feeding tests without reinforcement to check the acquisition of a conditioned flavour preference or aversion. In between, the anaesthetised pigs were subjected to three (18)FDG PET brain imaging coupled with an olfactogustatory stimulation with the conditioned flavours. During conditioning, the pigs spent more time lying inactive, and investigated their environment less after the F(LiCl) than the F(NaCl) or F(Glu) meals. During the two-choice tests performed one and five weeks later, the F(NaCl) and F(Glu) foods were significantly preferred over the F(LICl) food even in the absence of i.d. infusions. Surprisingly, the F(NaCl) food was also preferred over the F(Glu) food during the first test only, suggesting that, while LiCl i.d. infusions led to a strong flavour aversion, glucose infusions failed to induce flavour preference. As for brain imaging results, exposure to aversive or less preferred flavours triggered global deactivation of the prefrontal cortex, specific activation of the posterior cingulate cortex, as well as asymmetric brain responses in the basal nuclei and the temporal gyrus. In conclusion, postingestive visceral stimuli can modulate the flavour/food hedonism and further feeding choices. Exposure to flavours with different hedonic values induced metabolism differences in neural circuits known to be involved in humans in the characterization of food palatability, feeding motivation, reward expectation, and more generally in the regulation of food intake.     

The challenge of challenge: Can problem solving opportunities enhance animal welfare?

Cognitive mechanisms are an important part of the organization of the behavior systems of animals. In the wild, animals regularly face problems that they must overcome in order to survive and thrive. Solving such problems often requires animals to process, store, retrieve, and act upon information from the environment—in other words, to use their cognitive skills. For example, animals may have to use navigational, tool-making or cooperative social skills in order to procure their food. However, many enrichment programs for captive animals do not include the integration of these types of cognitive challenges. Thus, foraging enrichments typically are designed to facilitate the physical expression of feeding behaviors such as food-searching and food consumption, but not to facilitate complex problem solving behaviors related to food acquisition. Challenging animals by presenting them with problems is almost certainly a source of frustration and stress. However, we suggest here that this is an important, and even necessary, feature of an enrichment program, as long as animals also possess the skills and resources to effectively solve the problems with which they are presented. We discuss this with reference to theories about the emotional consequences of coping with challenge, the association between lack of challenge and the development of abnormal behavior, and the benefits of stress (arousal) in facilitating learning and memory of relevant skills. Much remains to be done to provide empirical support for these theories. However, they do point the way to a practical approach to improving animal welfare—to design enrichments to facilitate the cognitive mechanisms which underlie the performance of complex behaviors that cannot be performed due to the restrictions inherent to the captive environment.     

A lifetime perspective on foraging and mortality

Food intake carries many potential risks which may impair an animal's reproductive success not only in the current breeding cycle, but also for the rest of its lifetime. We examine the lifetime trade-off between the costs and benefits of food intake by presenting a simple animal foraging model, where each unit of food eaten carries with it a risk of mortality. We show that the optimal food intake rate over an animal's lifetime, for both semelparous and iteroparous animals, is not maximal. Instead, animals are required to strike a balance between the immediate reproductive benefits of gathering food and the future reproductive costs incurred by the food's mortality risk. This balance depends upon the lifespan of the animal as well as the nature of the risk. Different mortality risks are compared and it is shown that a mortality risk per unit time spent foraging is not, in general, equivalent to a mortality risk per unit of food consumed. The results suggest that a mortality risk per unit of food consumed, such as that presented by the presence of a toxin or of a parasite in the diet, has important consequences for feeding behaviour and is a possible factor involved in food intake regulation.     

Consequences of feeding for future feeding

The intake of food has physiological consequences via physical (e.g. distension) and chemical (e.g. glucose) stimulation of receptors in the viscera and, in the longer term, by changes in signals from adipose tissue (e.g. leptin), integrated by the CNS. These consequences are associated with the sensory properties of the food such that repeated exposure to a food generates a conditioned acceptance or rejection reflex with the physiological consequences of eating as the unconditioned stimulus (US) and the sensory characteristics of the food as the conditioned stimulus (CS). Such learnt preferences and aversions occur throughout the animal kingdom, from nematodes to human beings, with much of the research being carried out with insects, laboratory animals and farm animals. Preferences for and aversions to particular foods are manifested in non-random choices between two or more foods on offer but also influence the quantity eaten when only one food is available. These considerations have been developed into a theory of Minimal Total Discomfort which proposes that an animal experiments with the amount eaten per day, and its selection between different foods, until the total of the signals generated from excesses or deficiencies of food components is minimised. Changes in food composition and/or nutrient requirements can therefore be matched by appropriate changes in intake and selection.     

The use of the tongue and hyoid apparatus during feeding in lizards (Ctenosaura similis and Tupinambis nigropunctatus)

The use of the tongue and hyoid is examined in cineradiographic and electromyographic investigations of feeding in two species of lizards, Ctenosaura similis (Iguanidae) and Tupinambis nigropunctatus (Teiidae). In both animals food is transported through the oral cavity by regular cycles of the tongue. Tongue movements correlate with jaw and hyoid movement. Similarities between the two animals in the use of the tongue in food transport, lapping, pharyngeal packing, and pharyngeal emptying are detailed. Mechanisms of tongue protrusion are examined and it is shown that the tongue in Tupinambis is relatively more protrusible than in Ctenosaura. This difference is complementary with data on the greater reliance of Tupinambis on the tongue as a sensory organ. Tupinambis further differs from Ctenosaura in possessing a greater mobility of the hyoid. In many features of tongue use in food transport, lizards resemble mammals, supporting postulations of a basic pattern of intra-oral food transport. However, whether this pattern can be attributed to convergence or a common, primitive neural pattern of control cannot be distinguished. Lizards lack two major characteristics of mammalian food transport: regular masticatory cycles and an internal swallowing mechanism.     

Taste reactivity patterns in domestic cats (Felis silvestris catus)

The present study is aimed at finding taste reactivity patterns in domestic cats (Felis silvestris catus) which reflect 'liking' or perceived palatability. Three groups of nonstressed cats living in households were formed which a priori were expected to differ in motivational state for eating food items (more or less hungry), and which were offered two different food items differing in general taste properties (more or less flavourful food, MFF and LFF, respectively) around the time that they were fed their normal food. Analysis of the amount of food eaten showed that MFF was consumed regardless of hunger level and that LFF was consumed depending on the hunger level of cats: the more hungry cats ate more of LFF than the less hungry cats. Analysis of post-meal behavioural sequences showed that the 'MFF consumption sequence' differed from the 'LFF refusal sequence' and that the 'LFF consumption sequence' strongly resembled the 'MFF consumption sequence' but also contained elements of the 'LFF refusal sequence'. Subsequent analysis of the frequencies and total durations of behavioural patterns showed that two kinds of patterns existed, possibly reflecting two 'palatability dimensions': hedonic taste reactivity patterns (lick/sniff feeding bowl, lip lick and groom face) and aversive taste reactivity patterns (lick/sniff food and lick nose). These dimensions may be combined to obtain a single palatability score.