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La conduite de la plupart des troupeaux de vaches allaitantes, basée sur l’utilisation de l’herbe pâturée ou conservée, est déjà extensive. Modifier la date de vêlage permet d’adapter la conduite du troupeau aux ressources fourragères. Lorsque la production d’herbe est suffisante pour satisfaire les besoins alimentaires du couple vache-veau, faire vêler les vaches au début de la période de végétation accroît la part de l’herbe pâturée dans l’alimentation du troupeau et limite ainsi les besoins en fourrages récoltés. Inversement, si la production des prairies est insuffisante, les vaches peuvent vêler pendant l’hivernage et être taries au pâturage. Leurs performances de reproduction sont alors préservées. Dans ces conditions plus difficiles, la durée de lactation peut être raccourcie, ce qui dissocie les besoins de la mère et du jeune. Les troupeaux de bovins allaitants peuvent contribuer à l’entretien des espaces herbagers avec des ajustements de la conduite du pâturage, par exemple en allongeant la durée de pâturage au-delà de la période de végétation active. Une augmentation du chargement à certaines périodes clés limite l’extension de végétations indésirables. Les races adaptées aux conditions extensives se caractérisent par leurs bonnes aptitudes maternelles et leur aptitude à mobiliser puis reconstituer leurs réserves corporelles et à ingérer des fourrages grossiers., Suckler herd management, based on the maximal use of grazed or harvested grass, is already extensive in most situations. Appropriate change of calving date fits herd management to seasonal variations in food supply, When grass production is sufficient, spring calving increases the proportion of grazed grass in the annual feed and reduces the need for harvested forages. If good forages are available for only a short time, the lactation period can also be shortened, which splits up the requirements of the dam and the calf. On the other hand, when grass production is low and/for grassland of poor quality, cows can calve in early wintering and be dried off when turned out at pasture. Their reproductive performance is thus maintained at an acceptable level. Suckler herds can contribute to the control and the maintenance of vegetation, for example by lengthening the grazing season far beyond the period of active vegetation growth. An increase in stocking rate at certain key periods can be used to control undesirable species efficiently. The genotypes adapted to extensive management conditions are characterized by their good maternal abilities, their relatively high intake capacity on roughages and low quality grass, and their ability to mobilise then recover body reserves.

Data from in vivo digestibility trials with four to six horses fed twenty-seven forage-based diets are used to calculate prediction equations for the digestibility of dry and organic matter, based on the crude ash (CA), crude protein (CP) and crude fibre (CF) contents of diets and faeces. The most precise prediction of drymatter digestibility (r.s.d. 5 0·032, R 2 5 0·80) was derived from a multiple regression including faecal (CP, CF) and dietary parameters (CF). Among faecal parameters, CP was the best single predictor of both digestibility (r.s.d. 5 0·040, r 2 5 0·63) and dietary CP content (r.s.d. 5 0·028, r 2 5 0·59). For biological reasons we propose a non-linear model that allows prediction of dry- and organic-matter digestibility from faecal CP content with reasonable precision (r.s.d. 5 0·038, 0·036, r 2 5 0·65, 0·74, respectively). This will be adequate for many studies, especially for free-living animals in rangelands.

It is now well established that domestic animals construct responses to their environment that depend on experience and on integration of several features of the environment, including social partners. This ability to be aware of the environment is not fully developed at birth but improves and varies through the animal's life. This topic is discussed on the basis of social processes in sheep and cattle. Social relationships of an animal with its conspecifics develop with age; they do not merely depend on pre-programmed behaviours but rely at least in part on learning of characteristics of the partners. Soon after birth, a strong preferential bond establishes with the dam then to a lesser extent, the young associates to other members of the flock, especially other young. The attractiveness of the group varies later in life due to external events or to physiological state: the abrupt separation from the dam at artificial weaning strengthens bonds between peers, whereas around parturition, females are less disturbed by isolation from the group. More recently, the awareness of social partners has been described in non-social contexts: the animal modifies its responses to events according to the presence of partners, and also to their emotional state and behaviour. The effects of partners seem to depend on their relationship with the animal and also on the social motivation of that animal, which both vary during its life. We recommend study of the ontogeny of awareness using the model of social influences.

Thirty-two cows (16 Montbeliardes and 16 Tarentaises) in midlactation were used in an experiment utilizing a 2 × 2 factorial arrangement of treatments. Throughout the trial, cows received first-cutting cocksfoot hay for ad libitum intake supplemented with a fixed amount of concentrate that was individually adapted to the milk yield of each cow. During a 23-d experimental period, one group of cows walked 9.6 km/d; the other group of cows remained in the barn. Cows that walked daily ate less hay (–1.3 and –2.1 kg/d of dry matter for Tarentaise and Montbeliarde cows, respectively) and yielded less milk (–1.7 and –2.5 kg/d for Tarentaise and Montbeliarde cows, respectively) than did cows that did not walk daily. A residual effect of walking on milk yield was observed during the 10 d following the experimental period. For both breeds, fat content and, to a lesser extent, protein content were higher (+6.4 and +1.0 g/ kg, respectively) for cows that walked. Somatic cell count was also higher for cows that walked (+115,000 cells/ml). This difference was more marked in cows that were initially infected by a minor or major pathogen (+185,000 cells/ml) than in uninfected cows (+47,000 cells/ml) and on the 1st d of walking when walking was linked to increases in pH, bovine serum albumin, and immunoglobulin G 1 contents of milk (+0.08 unit, +0.16g/L, and +0.19g/L, respectively). Throughout the experimental period, walking induced a rise in body temperature (+1°C) and in plasma nonesterified fatty acids (+0.63m M /L). On the 1st d of walking, plasma glucose, lactic acid, and cortisol contents were significantly higher for cows that walked (+0.25g/L, +0.64g/L, and +28.8ng/ml, respectively).

National audience; A better understanding of the animal x plant interaction is needed to develop management practices which will maintain a sufficiently rich and abundant vegetation in the pastures. Such practices would permit the animals to meet their nutritional requirements, and to ensure a sufficient production, while contributing to the maintenance of the environment. This review, drawn on a large number of experimental studies, takes stock of the factors influencing the selection and use of feeding sites and stations by herbivores. First, we present the theorical framework in which the experimental observations are discussed. The general context of Optimal Foraging Theory (OFT) and its predictions are described and discussed. Second, we analyse how forage (quantity and quality, plant species, distribution), environment (topography, distance to water, predator risk) and some animal factors (cognitive abilities, social organization) affect the choice and use of feeding sites and stations. The OFT successfully explains the foraging behaviour of herbivores. However, animals' choices are rarely as absolute as predicted. Under natural conditions, animals not only respond to food resource, but they are also constrained by some non alimentary environmental factors and by the limits of their cognitive abilities (memory, discrimination). Other complementary approaches, such as hedonism,, and nutritional wisdom, can partly influence animals' choices and are also briefly discussed.; Mieux comprendre la relation animal-végétation est nécessaire pour développer des systèmes de gestion qui favorisent le maintien par le pâturage d’une ressource suffisamment riche et abondante. Dans ces conditions, l’animal peut couvrir ses besoins nutritionnels et assurer une productivité suffisante, tout en participant à l’entretien du milieu. L’article fait le point, à partir d’un grand nombre de travaux expérimentaux, sur les facteurs qui influencent la sélection et l’utilisation des sites et stations alimentaires par les herbivores. La première partie est consacrée au cadre théorique dans lequel sont discutées les observations expérimentales. Le contexte général de la Théorie de l’Alimentation Optimale (TAO) et ses prédictions, sont décrits. L’’applicabilité’, l’utilité et la validité des modèles d’optimisation dans l’étude du comportement alimentaire des herbivores sont tout particulièrement considérées. Ensuite, est étudiée l’influence des différents facteurs, trophiques (quantité et qualité des ressources fourragères, espèce végétale), environnementaux (topographie, distance aux points d’eau, présence d’abris et risques de prédation) et animaux (capacités cognitives et organisation sociale) sur la sélection et l’utilisation des sites et des stations alimentaires par les herbivores. La TAO permet d’expliquer les stratégies alimentaires des herbivores. Cependant, les choix des animaux ne sont en général pas aussi absolus que ceux prédits. En conditions naturelles, les animaux répondent non seulement à la ressource alimentaire, mais aussi à différentes contraintes externes (environnement non alimentaire) et internes (mémoire, discrimination). D’autres approches complémentaires, telles l’’hédonisme’ et la ’sagesse nutritionnelle’, susceptibles d’influencer les choix des animaux, sont brièvement analysées.

International audience

L'intensification de la production ovine française a été mise en difficulté par l'élargissement de l'Organisation commune de marché de l'Union européenne à la Grande-Bretagne et à l'Irlande, puis par la réforme de la PAC qui soutient les systèmes moins intensifs. L'étude montre la spécificité d'élevages extensifs au sein d'un groupe de grands élevages ovins viande du Montmorillonnais (zone défavorisée du sud de la Vienne) regroupés en types d'exploitations très caractérisés, relativement aux conditions du milieu. Les fonctionnements sont très différents, y compris au sein des élevages extensifs. De bons niveaux de revenu s'observent autant chez certains élevages intensifs que dans les élevages herbagers autonomes ou extensifs spécialisés, en fonction des niveaux des trois facteurs essentiels que sont la marge par brebis, la productivité du travail et les charges de structure. En élevage extensif, les meilleurs résultats reposent sur une productivité numérique modérée avec une utilisation maximale de l'herbe et très peu d'intrants. Il faut généralement pouvoir disposer de plus grandes surfaces qu'en intensif. Cependant, certains élevages extensifs obtiennent de bons résultats sur des surfaces moyennes, s'ils ont une excellente autonomie fourragère et des charges de structure très limitées., The expansion of the European Union Common Market Organization to include Great Britain and Ireland has made intensification of French sheep production difficult, This situation is aggravated by the PAC reform which supports systems that are less intensive, This study demonstrates the special character of extensive farms located in the midst of a group of large meat sheep farms in Montmorillonnais (an unfavourised zone south of Vienne, France), Characteristic production systems are found in this region, and the type of farming system ranges from extensive (With a stocking rate of less than 0.85 LU/ha PFS) to intensive (1.40 LU/ha PFS). There are large differences between the ways the systems function, even between the various extensive systems. Two subgroups can be distinguished among these latter, The first include extremely autonomous extensive specialists and the second are extremely extensive systems with crops, Some intensive farmers make a decent net income as do some graziers and specialized extensive farmers, The three essential factors ape the margin per ewe, the work productivity anti the infrastructure costs, On extensive farms, the best results are found for a moderate numerical productivity (1.15-1.30 lamb per ewe), which make maximal use of grazing, The extent to which grazing is used can be measured by the farm's degree of forage autonomy and the minimal amount of input required, On farms using this kind of system, lambing occurs preferentially at the end of Winter (December to April) so that the lambs can be sold early and the animals can spend more time in pasture, thereby reducing the amount of hay needing to be harvested, In general, the land area required is greater than that required in intensive farming, However, some extensive farms with small usable agricultural areas can obtain good results if they have a high degree of forage autonomy and if their infrastructure costs are Limited.

Charolais cows were individually given hayad libitumaround calving for two successive winters (no. = 40 and no. = 43). Profiles of hay intake are defined for each cow as the evolution of individual daily intake level around calving.The aim of this work was to build a typology of these profiles, using multivariate analysis. Four and three groups of cows were distinguished respectively for a 2-month and a 4-month period around calving (PI and PI). These groups corresponded to different kinetics of intake level around calving which were defined as follows: group 1 — plane profiles, with a low difference of intake level between pregnancy and lactation; group 2 — profiles characterized by a marked decrease in intake level just before calving followed by a long and regular increase after calving; group 3 — profiles with no decrease before calving but an early break in the increase in intake after calving; group 4 — intake profiles with a large difference in intake level between pregnancy and lactation. Groups 2 and 3 were pooled for P2.Cows from groups 2 and 4 increased intake after calving fast enough to prevent the use of their body reserves even with a high milk-production level. Their calculated energy balance became positive very quickly, only 1 week after calving. At the other extreme, a decrease in body reserves was observed for cows which needed at least 1 month after calving to reach their maximum intake capacity and then recover a positive energy balance.

Cent-quarante trois exploitations laitières dans 2 zones du Massif Central ont fait l’objet d’une enquête détaillée concernant à la fois la structure de l’exploitation et du troupeau, l’utilisation des surfaces, les pratiques alimentaires hivernales et estivales, les pratiques de traite et l’hygiène des animaux. Parallèlement des caractéristiques du lait (taux butyreux et protéique, numération cellulaire, flore totale et contamination butyrique) ont été relevées mensuellement pendant 14 mois. Ces données ont permis d’analyser la variabilité des caractéristiques du lait en fonction des caractéristiques des exploitations. En dehors de l’effet de la race des vaches laitières, ce sont des variables de maîtrise de l’alimentation qui permettent le mieux d’expliquer les variations de la composition chimique du lait (nature du fourrage et niveau des apports nutritifs). La qualité bactériologique du lait a pu être associée à la fois à la nature des fourrages hivernaux (contamination butyrique) et à l’hygiène de traite. Dans la plupart des exploitations, la numération cellulaire a été sensiblement plus élevée en été qu’en hiver. Peu d’exploitations présentent à la fois un taux protéique élevé et des caractéristiques hygiéniques du lait optimales. Dans les 2 zones, c’est au cours de l’hiver que l’on observe la plus grande variabilité de composition du lait, liée aux différences de conduite alimentaire hivernale. D’une manière générale, l’hygiène du lait reste peu maîtrisée dans un grand nombre de troupeaux, et, dans la majorité des exploitations de la zone Nord, l’alimentation hivernale semble insuffisante pour assurer l’expression d’un taux protéique élevé., One hundred and fourty three dairy farms located in Massif Central were included in a detailed survey involving the herd and the farm structure, winter and summer feeding practices, milking and hygiene practices, and cows characteristics and management (breed, calving distribution...). These data allowed analysis of the variations of milk characteristics (fat and protein content, somatic cell count, total bacterial count, butyric spore count). Milk chemical composition differences among farms were higher in winter than in summer, and resulted essentially from breed and feeding practices (nature of the forages and nutritive supplies). Milk bacterial quality resulted both from the nature of winter forages and milking hygiene. In most of the farms, somatic cell count was higher in summer than in winter. Few farms had both a high protein content and a high milk hygienic quality.

Persistence of individual differences in animal behavior in reactions to various environmental challenges could reflect basic divergences in temperament, which might be used to predict details of adaptive response. Although studies have been carried out on fear and anxiety in various species, including laboratory, domestic and wild animals, no consistent definition of fearfulness as a basic trait of temperament has emerged. After a classification of the events that may produce a state of fear, this article describes the great variability in behavior and in physiological patterns generally associated with emotional reactivity. The difficulties of proposing fearfulness--the general capacity to react to a variety of potentially threatening situations--as a valid basic internal variable are then discussed. Although there are many studies showing covariation among the psychobiological responses to different environmental challenges, other studies find no such correlations and raise doubts about the interpretation of fearfulness as a basic personality trait. After a critical assessment of methodologies used in fear and anxiety studies, it is suggested that discrepancies among results are mainly due to the modulation of emotional responses in animals, which depend on numerous genetic and epigenetic factors. It is difficult to compare results obtained by different methods from animals reared under various conditions and with different genetic origins. The concept of fearfulness as an inner trait is best supported by two kinds of investigations. First, an experimental approach combining ethology and experimental psychology produces undeniable indicators of emotional reactivity. Second, genetic lines selected for psychobiological traits prove useful in establishing relationships between behavioral and neuroendocrine aspects of emotional reactivity. It is suggested that fearfulness could be considered a basic feature of the temperament of each individual, one that predisposes it to respond similarly to a variety of potentially alarming challenges, but is nevertheless continually modulated during development by the interaction of genetic traits of reactivity with environmental factors, particularly in the juvenile period. Such interaction may explain much of the interindividual variability observed in adaptive responses.

Les bovins des races rustiques allaitantes ont des caractéristiques physiologiques qui leur permettent de s’adapter à des conditions difficiles et d’y maintenir assez bien leurs productions. Là où les ressources alimentaires sont limitées, ils maintiennent mieux leur développement squelettique au-delà du sevrage que ceux de race à viande à fort potentiel de croissance musculaire. De même, les femelles (au moins de certaines races rustiques) soutiennent mieux leur production laitière et leur reproduction lorsqu’elles font appel à leurs réserves corporelles dans les toutes premières années de vie productive. Cela pourrait être attribué à une maturité plus précoce, accompagnée d’une quantité plus importante de tissu adipeux aisément mobilisable et de besoins de croissance devenus moins élevés. L’aptitude à l’allaitement des vaches Aubrac et surtout des vaches Salers est élevée. Elles sont capables de vêler plus tôt au cours de l’hivernage que les vaches des races à viande, ont un intervalle entre le premier et second vêlage plus réduit (anoestrus plus court, durée de gestation plus faible). La capacité d’ingestion de fourrages grossiers est satisfaisante chez les bovins de races rustiques, mais inférieure à celle de types plus laitiers. Les races rustiques présentent aussi d’autre capacités d’adaptations physiologiques et comportementales à l’environnement (climat, pâturages), qu’il conviendrait de préciser., The cattle of hardy breeds have special physiological characteristics that enable them to adapt to difficult environments and to maintain their productivity to some extent. Some results obtained more particularly at the INRA experimental farms located in the highlands of Auvergne prove these abilities. In areas with restricted food resources, hardy breeds seem able to maintain during the rearing period better growth, espacially of their skeleton (height of the withers), than beef breeds with high muscular potential. This could result from smaller adult size and/or earlier maturity. Like other types of cows, those of hardy breeds mobilize their body reserves during food shortage and then recover them during grazing. Their special feature seems to lie in their ability to maintain their milk yield and reproduction better than beef breeeds do, when they use their reserves in the first years of productive life. This could also be attributed to earlier maturity, going with a greater quantity of adipose tissue, which is easy to mobilize, and with reduced growth requirements. Most females of hardy breeds are sexually earlier maturing than beef breeds. They are also able to calve earlier in season, even in difficult food conditions. They maintain better a short interval between first and second calving, mainly because of a shorter post-calving anoestrus and also a shorter gestation period. It is also in these extreme conditions (Ranch ITEB-INRA, 1972-76) that Aubrac and Salers cows gave better overall reproductive performances than Charolais and Limousin ones, espacially during their two first years of production. The suckling ability of the Aubrac and above all of the Salers cows rank them among the best French suckling cows, mainly due to their dairy origin. It is fully expressed among young cows, and milk production of young Salers cows is less reduced in difficult food conditions than the one of French specialized beef cows. This production ensures their calves satisfactory live weight gain with limited complementary concentrate expenditure, in particular since it maintains well at the end of suckling period. The intake capacity of roughages is satisfactory among cattle of hardy breeds but remains lower than in specialized dairy breeds. Hardy breeds seem to have other assets, espacially in their behavioural adaptations to difficult pastures (travels, eating rate), which should be studied. The extreme limits of use of hardy breeds should also be studied, especially females’capacity to mobilize their body reserves, with regard to reproduction.

International audience; Individual milk production curves of 542 cows with 722 cases of mastitis were compared with control curves drawn from healthy lactating cows. First, differences were classified into patterns of milk loss, and their distribution was analyzed among the patterns with regard to breed, season, lactation number, stage of lactation, and milk production. Then, individual milk losses were estimated and analyzed according to the same factors. In early lactation, almost 7% of mastitis cases necessitated culling or drying off. For 36% of the cases of mastitis occurring in early lactation, milk production was affected for an extended period, and the milk loss induced was 911 kg on average over the entire lactation. Fifty-two percent of the mastitis cases occurring after lactation peak was not accompanied by marked modifications of the lactation curves. For 38% of cases of mastitis occurring from mid to late lactation, milk production was affected for an extended period. When milk production was the most affected (26% of total cases), the average loss was 850 kg over the entire lactation. For cases in early or mid to late lactation, the production at mastitis onset was a determining factor of the amount and pattern of milk production loss induced. Results were applied in a simulation over two simulated groups of cows

26 ref.; National audience; In French Guiana, zootechnical research run by INRA, within the developpement program called “Plan-Vert” initiated in 1975, were specially focused on cattle rearing (zebu Brahman), in order to increase local beef meat production. Most of the technical datas concern reproductive performances under tropical climate and rearing of bulls on pasture between weaning (9 to 10 months of age) and slaughtering (24 to 30 months of age). In addition, the control of performances of private herds from 1985 to 1987, have contributed to analyse “on-farms” technical results.This has been the first step towards a typology based on management practices of the farmers. Investigations and studies about other species (pigs, poultry, rabbits) have led to conclude, regarding the number of farmers involved, that beef production is not prevailing in French Guiana. The main characteristic of breeding systems is the diversification of the productions (one farm : many species), in order to adapt to the local market, and to satisfy their necessity of cash-flow. In this situation, where diversification of rearing activities is valuable, local wild species could turn out to be an interesting way to valorize the natural biological resources of French Guiana. Up to now, two species have been studied in this respect, a local rodent : the c yabia (Hydrochoerus hydrochaeris), and a freshwater fish : the atipa (Hoplosternum littorale). In conclusion, considerations about necessary conditions to develop sustainable breeding systems in French Guiana are presented. They stress the idea that taking into account economical and sociological aspects is of a special importance in the guianese context.; Les travaux à caractère zootechnique réalisés par l’INRA sur sa station expérimentale dans le cadre du Plan Vert, ont surtout concerné l’élevage bovin à viande (zébu Brahman). Ils ont permis l’acquisition de résultats portant sur les performances de reproduction en milieu équatorial, et la conduite des taurillons à l’herbe entre le sevrage (âge de 9 à 10 mois) et l’abattage (âge de 24 à 30 mois). Parallèlement, entre 1985 et 1987, des suivis de troupeaux privés ont permis l’analyse des résultats techniques des élevages locaux, ainsi que l’ébauche d’une typologie des exploitations basée sur les pratiques des éleveurs. Plusieurs enquêtes, ainsi que des études par filières (porcine, avicole, cunicole) ont également montré que, relativement à l’ensemble de l’activité agricole, la production de viande bovine était loin d’être prédominante en Guyane. Une caractéristique importante des exploitations pratiquant l’élevage s’est avérée être la diversification de leurs spéculations, gage de souplesse, de capacité d’adaptation au marché et aux besoins de trésorerie, et donc de leur pérennité. D’autre part, l’élevage de certaines espèces sauvages autochtones pourraient, dans ce contexte de diversification des spéculations, constituer une alternative intéressante par la valorisation des ressources biologiques naturelles de la Guyane. Deux espèces ont déjà fait l’objet d’études : un mammifère rongeur, le cabiaï (Hydrochoerus hydrochaeris) et un poisson d’eau douce, l’atipa (Hoplosternum littorale). Illustrées par ces exemples, quelques pistes de réflexion sont présentées concernant les conditions d’émergence de systèmes d’élevages pérennes en Guyane. Elles soulignent notamment l’importance de la prise en compte des aspects autres que techniques (principalement économiques et sociologiques) pour l’appui au développement de l’élevage dans le contexte très particulier de la Guyane.

Cent trente sept vaches laitières de race Pie-Noir (41), Montbéliarde (42) ou Tarentaise (54), en première ou deuxième lactation, ont reçu au cours de l’hiver deux niveaux d’alimentation énergétique (haut: H et bas : B), et ont été ensuite alimentées de manière identique au pâturage. Des mesures individuelles de la composition chimique du lait et de son aptitude à la coagulation ont été réalisées 3 fois pendant l’hiver et 2 fois au pâturage. Chez les Pie-Noir, les taux de caséines et de calcium et l’aptitude à la coagulation (temps de raffermissement et fermeté du gel) ont été inférieurs (P, One hundred and thirty Holstein (41), Montb6liardes (42) and Tarentaises (54) dairy cows in first or second lactation received during winter one of two levels (high, H ; low, L) of energy intake, and were later fed identically at pasture. Three times in winter and twice at pasture, individual measurements of milk chemical composition and coagulation properties were performed. Milk from Holstein cows had lower casein and calcium contents, and poorer coagulation properties (curd firming time and curd firmness) than that from Montbéliardes and Tarentaises (P

International audience; Environmentally induced stereotypies, commonly observed in farm and zoo animals, are behaviors that are relatively invariant, that are regularly repeated, and that serve no obvious function. However, there is as yet no accepted means of discriminating between normal and abnormal behavior, and the assumption that stereotypies are abnormal may mask the fact that they arise in part through processes that "normally" control behavior. There is growing evidence that stereotypies in sows and broiler breeders are strongly related to feeding motivation. For example, sows only develop oral stereotypies if their feed intake is restricted, and operant conditioning experiments have shown commercial levels of feed restriction to give rise to high levels of feeding motivation. Stereotypies in animals whose feed intake is restricted largely occur in the postprandial period, and ingestion of food has specifically been shown to elicit stereotypies in sows. These observations suggest that positive feedback from feeding produces a short-term increase in feeding motivation that at the end of the meal is directed toward available, alternative stimuli such as chains, the choice of stimuli reflecting the sensory feedback from the activity. Drinking behavior may also become an expression of feeding behavior after metabolic water requirements are met. In addition to these processes specific to feeding motivation, it seems likely that nonspecific processes, which operate more generally across motivational systems, contribute to the persistence of the behavior. Behavioral arousal may facilitate performance of active behaviors, and sensitization of the underlying neural elements may lead to the behavior being more easily elicited and maintained. A crucial factor in the sensitization process would seem to be the channeling of complex behavior by the environment into a few and very often repeated sequences of behavior. This approach suggests that stereotypies can be prevented by either reducing the level of motivation underlying the stereotypy, or by allowing for the expression of more complex behavior and thereby preventing the processes of channeling and sensitization from occurring.

Four rumen-fistulated cows, fed maize silage (n = 2) or hay (n = 2), were administered glycerol (240 g and then 1200 g dry matter (DM)) daily through the cannula, after a control period. In vitro fermentations (five or six per cow, two of which were carried out during the control period) showed that the ability of rumen liquid to degrade glycerol increased with the amount of glycerol administered and was slightly higher when samples came from cows fed maize silage. Microbial adaptation seemed immediate, as the maximal rate of degradation was achieved on the first day. The relative proportions of propionic (C3) and butyric (C4) acids in the volatile fatty acid (VFA) mixture of the fermenter fluid increased at the expense of acetic acid (C2). In vivo, the 240 or 480 g glycerol administered in the rumen on the days of measurements had disappeared on all but one occasion 4 h afterwards. In the VFA, the proportion of C4, and, to a lesser extent, that of C3, increased. The proportions of the glycerol absorbed and that transformed into C3 amounted to 35–69% of the amount administered (240 g), according to the rate of glycerol disappearance used in the computations.

Soixante-seize exploitations laitières utilisant des vaches Montbéliardes à haut niveau de production (6200 à 8800 kg/vache/an) et alimentées l’hiver avec une ration à base de foin, ont fait l’objet d’une enquête détaillée concernant à la fois la structure de l’exploitation et du troupeau, la qualité des fourrages utilisés, les pratiques alimentaires hivernales et estivales et les caractéristiques génétiques des animaux (index et effet troupeau pour le lait, le taux butyreux et le taux protéique). Ces données ont permis d’analyser les variations de la composition chimique du lait d’une exploitation à l’autre. Les taux butyreux et protéique moyens annuels ont été très variables d’une exploitation à l’autre (respectivement 34,2 à 41,2 g/kg et 30,7 à 34,5 g/kg), malgré l’homogénéité des exploitations sur les critères niveau de production laitière, race et type de ration de base. Cette variabilité est due essentiellement à des facteurs du milieu. Lorsque l’on classe les exploitations par niveau d’effet troupeau (taux butyreux ou taux protéique), on observe 1) que les écarts de taux protéique sont les plus élevés au cours de la période hivernale et sont associés à des pratiques alimentaires différentes (qualité des foins, part du regain dans la ration, type de concentré utilisé), 2) que les écarts de taux butyreux d’un groupe d’exploitations à l’autre sont aussi importants, voire plus, l’été que l’hiver. Ces écarts ne sont qu’en partie associés à des pratiques alimentaires favorables ou défavorables au taux butyreux (présence de betteraves dans la ration, méthode de distribution du concentré). On n’a pas observé de liaison entre les effets troupeau taux butyreux et taux protéique. Il est donc possible de faire varier ces 2 taux de manière indépendante, par le biais de facteurs du milieu., Seventy-six dairy farms composed of high-producing (6200 to 8800 kg/yr) Montbéliarde cows that were fed hay-based rations were included in a detailed survey involving the herd and the farm structure, quality of forage, winter and summer feeding practices, and genetic characteristics (breeding value and herd effect for milk production, fat concentration, and protein concentration). These data permitted analysis of the variations of milk composition among farms. The mean annual fat and protein concentrations varied greatly among farms in spite of the homogeneity of the farm sample with regard to milk produced, breed, and type of winter roughage. Such variability results essentially from environmental factors. When farms were classified according to their level of herd effect (fat or protein concentrations), 1) protein concentration variations were greater in winter and linked to different feed characteristics (hay quality, type of concentrate), and 2) variations in fat concentration among farm groups were as marked, if not more so, in summer than in winter. These variations are only partly linked to feeding practices that are beneficial or detrimental to fat concentration (presence of sugar beet in the ration, concentrate distribution method). No correlation occurred between fat and protein herd effects. Therefore, these two variables may be controlled independently by manipulating environmental factors (especially feeding factors).

Four experiments were designed to find evidence of observational learning in cattle. The experiments were run on ten experimental heifers, each observing a demonstrator mate performing a task, and on ten control heifers, each observing a non-demonstrator mate. The mates and observers were separated by wire netting in Experiments 1–3, but were in the same room in Experiment 4. The task to be learned was to push a panel to get food into a box. All naive animals were able to observe while their mate performed the task. The observers in Experiments 1 and 4 were Salers heifers that had no prior experience of the testing room; those in Experiment 2 were Salers heifers that were accustomed to the room; those in Experiment 3 were Aubrac or Limousin heifers that had already eaten in the room. The behaviour of the observers was influenced by their mates: activity at or near the boxes was enhanced by the presence of demonstrators in Experiment 2 (box contacts: 38.0 ± 16.2 vs. 22.1 ± 11.9 for experimental and control heifers, respectively; P 0.05). The time spent eating was longer when the observer only had visual contact with a demonstrator (Experiment 1: 15.9 ± 1.6 vs. 11.6 ± 1.8 min), but was lower when physical contacts with the demonstrator were possible (Experiment 4: 4.6 ± 8.8 vs. 5.4 ± 2.2 min; P

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Résumé de communication; International audience

Beef and dairy products suffer from a negative health image, related to the nature of their lipid fraction. Rumen lipid metabolism involves the presence of saturated lipids in ruminant tissues. Lipolysis, fatty acid biohydrogenation and formation of microbial fatty acids in the rumen and their effects on rumen outflow of fatty acids are discussed. Special emphasis is given to the formation of trans-fatty acids and the possibilities of decreasing biohydrogenation. Small differences in intestinal digestibilities of fatty acids are mentioned, followed by a discussion on transfer of absorbed fatty acids into milk and adipose tissue lipids. The preferential retention of polyunsaturated fatty acids as well as the balance between synthesis and incorporation of fatty acids in tissues is described. Dietary means for the modification of milk fat are listed, with special emphasis on the possibilities for enrichment in polyunsaturated fatty acids and the presence of conjugated linoleic acids. A description of the nature and development of fat depots in beef cattle is followed by a discussion of breed, conformation and feed effects on adipose tissue distribution and fatty acid composition. Special emphasis is given to the very lean Belgian Blue double-muscled breed. The review ends with a consideration of the limits to the modification of ruminant fats, involving considerations of consumer acceptance as well as animal welfare and environmental effects.

Communication nø 14; International audience

Our objective was to test whether the effects of space allowance on social interactions, activity patterns and growth rates of hinds reared at pasture in single-species groups, were modified by mixing them with ewes. Thirty individuals of each species were assigned to two single-species groups of 10 animals (hinds: H1 and H2, ewes: E1 and E2) and to two mixed-species groups of 5 hinds and 5 ewes (M1 and M2). For 28 days, H1, E1 and M1 were kept at high space allowance (HSA: 267 m 2 /animal) and H2, E2 and M2 at low space allowance (LSA: 67 m 2 /animal) and for the following 28 days, the space allowance was reversed. Mean interindividual distances in single-species groups were lower at LSA than at HSA (hinds: 10.0±0.3 vs. 15.4±4.8 m, P P P P P

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Résumé de communication + poster, abstract 550; International audience

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International audience; Feeding jars were used to feed nymphs of Amblyomma variegatum on blood of goats or cattle. Sterile blood was collected daily or weekly (kept at 4 degrees C or frozen until use), with addition either of heparin alone or of heparin and antibiotics/fungicide or of heparin, adenosine triphosphate and glutathione. Membranes were made of a thin (0.12-0.32 mm) film of silicone mastic. Blood in the jars was replaced twice a day, and reached a temperature of 39 degrees C in a waterbath before it became available to the ticks. Attachment of nymphs was stimulated by dropping on the membrane fresh goat hair and squamae collected close to prefed males, skin washing and natural pheromone extracts. Using these devices, attachment of nymphs is rapid and intense (68%). Their body mass when engorged and the molting success, were lower than that of naturally fed ticks. Furthermore, the proportion of engorging ticks was usually much less and the length of the blood meal was much longer than of naturally fed ticks. The best results were obtained with fresh goat blood or cattle blood with antibiotics. Further developments are needed before this method can be used routinely.

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Several lines of evidence suggest that carotenoids may have a beneficial effect on health as a result of their antioxidant properties. In addition to beta-carotene, five other carotenoids are recovered in noticeable amounts from human plasma and tissues. Although the effect of beta-carotene on in vivo lipid peroxidation has been documented, few data are available on the effects of the other carotenoids. We evaluated the ability of the main human carotenoids to reduce lipid peroxidation by determining the correlations between plasma carotenoid concentration and plasma antioxidant capacity (in 79 healthy volunteers) and between carotenoid status and breath pentane excretion (in a subgroup of 24 subjects). Carotenoid intake was assessed by means of a 3-day food recall. Carotenoid status was evaluated by measurement of beta-carotene, lycopene, lutein/zeaxanthin, and alpha-carotene in plasma and buccal mucosal cells. Antioxidant status was evaluated by measurement of the total antioxidant capacity of the plasma. Oxidative stress status was evaluated by breath pentane measurements. Food recall data and the carotenoid concentrations in plasma and buccal mucosal cells showed that the subjects had normal carotenoid intake and normal carotenoid status. The total antioxidant capacity of the plasma was not related to the concentration of any specific carotenoid. The level of expired air pentane was not related to the carotenoid status of the subjects. These results show that normal concentrations of carotenoids in plasma and tissues are not correlated with these clinical markers of antioxidant and oxidative stress status.

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