Quels "besoins" du poulet de chair en acides aminés essentiels ? Une analyse critique de leur détermination et de quelques outils pratiques de modélisation

National audienceTo balance the feed levels in essential amino acids, nutritionists use tables containing average requirements stemming from bibliographical surveys. Result of experiments studying essential amino acid requirements, depend both on the criterion to be optimized (growth rate or feed efficiency) and on the methodology adopted for analysing the results. From an experiment to the other, environmental conditions and chicken genotype may also explain a part of the observed variability of the requirements. To cope with this variability, the results from numerous experiments obtained mainly in fast growing broilers raised under optimal conditions are pooled but the results of those grouped analyses are not precise, and this impairs the application of measured amino acid requirements to field conditions. Mechanistic models integrating basic knowledge of the energy and protein metabolism might constitute additional tools to quantify the effects of an essential amino acid level on broiler performances under different conditions. Models not only synthesise the knowledge acquired by various experiments but also take simultaneously into account the multiple interactions among factors of variation. There are some marketed models measuring the effects of the main feed characteristics (essential amino acids, energy etc.) and raising conditions on chicken growth. Their results seem precise enough for an application but they are presented as "black boxes" and the complexities of their functioning make them difficult to update. INAVI is a model fully open to the user that might be more adapted to the diversity of production systems. Prediction of the growth of the chicken by INAVI is based on the effects of environmental and nutritional factors on feed intake regulation.Pour équilibrer les acides aminés essentiels d’un régime, le nutritionniste dispose de tables de recommandations moyennes issues de méta-analyses bibliographiques. L’estimation du besoin en un acide aminé essentiel dépend du critère de production que l’on cherche à optimiser et de la méthodologie adoptée pour analyser les résultats expérimentaux. Les conditions d’élevage et les types d’animaux étudiés expliquent une autre part de la variabilité des recommandations. Les moyennes issues des méta-analyses de données bibliographiques sont finalement assez peu précises et d’autant plus difficiles à adapter aux conditions pratiques qu’elles concernent essentiellement les poulets de chair à croissance rapide dans des conditions optimales. L’intégration des bases du métabolisme énergétique et protéique à l’aide de modèles mécanistes peut constituer un moyen complémentaire de quantifier les effets d’une recommandation en acide aminé essentiel dans des conditions variables. La modélisation permet non seulement la synthèse des connaissances acquises par l’expérimentation, mais également la prise en compte des interactions multiples entre plusieurs facteurs de variation. Dans la pratique, les modèles commercialisés permettent de mesurer les effets des principales caractéristiques de l’aliment et des conditions d’élevage sur la croissance ou les besoins en acides aminés des poulets de chair. Leurs résultats semblent suffisamment précis pour une utilisation pratique, mais leur présentation de type « boîte noire » et la complexité de leur fonctionnement sont un frein à leur mise à jour ou à leur adaptation à de nouveaux modes de production. Le modèle INAVI, présente une structure plus ouverte à l’utilisateur qui permet une meilleure adaptation aux diverses situations d’élevage. INAVI prédit la croissance des animaux en se basant sur l’effet des conditions d’élevage et d’alimentation sur l’ajustement de l’ingestion

Digestibilities of broilers fed 18 different diets at 3 ages

International audienc

AVIBIO : une methode et un outil pour évaluer la durabilité des filières avicoles biologiques

The French organic poultry sector is facing new challenges relating to contexts at different geographical scales: global, European and national, including specificities of each production region. In order to evaluate what is required to meet the increasing demand for organic poultry, while moving towards sustainable production, a method and a tool to assess sustainability at the production chain scale was carried out within the framework AVIBIO project. Four regions were studied: Bretagne and Rhône-Alpes for eggs, Pays de la Loire and Aquitaine for chickens. A participative approach was undertaken in order to promote exchange between the various players who are involved directly or indirectly in the production chain (production organizations, farmers, professional unions, researchers, local authorities, consumers, etc.). For each sustainability component (economic, environmental and social), indicators were fixed based on criteria which refer to the principles corresponding to the stakeholders' representations of sustainable development. A scoring scale was attributed to each indicator: high scores corresponding to the objectives being met. Scores were added per criteria and principle for each component. For the four regions, the final evaluation highlighted five ways of improvement and serves as a decision-making tool for the different stakeholders. The evaluating tool connected with AVIBIO was implemented through both an Excel® file and a User's Guide, each indicator being documented. The tool and guide are downloadable from the web page of AVIBIO within the website of RMT DévAB (www.devab.org/AVIBI

Experience with a variety of feed colours reduces feed neophobia in the turkey

When exposed to a new feed, farm birds are commonly reluctant to eat this feed. This phenomenon, called feed neophobia, could be reduced by exposing young animals to a variety of novel feeds. We investigated whether previous experience with a variety of feed colours could reduce food neophobia in turkeys. We hypothesised that both greater variety in visual experience and frequency of changes would increase the acceptance of novel feeds. To test this hypothesis, hatchling turkeys were exposed to a 28-day feeding regime differing in feed colours and frequency of feeding transitions. There were 3 experimental groups: one group was exposed to only one colour of feed (C0 group); the second group was exposed to green and red feeds on alternate weeks (low change rate: LC group) and the third group was exposed to green and red feeds changed randomly each day (high change rate: HC). As the contrast between the novel colour and the familiar feed could also influence bird responses, two subgroups were constituted within each experimental group: one receiving green feed and the other red feed before the novel feed test (i.e. C0 red, C0 green; LC red, LC green; HC red, HC green). From D29 to D31, all birds were exposed to blue, light-green or white novel feeds for 5 min each. Short-term feed intake (5 min) was measured the day before change-over and at each change-over on the three subsequent test-days. All groups were found to eat less of the novel feed than the familiar feed but this difference varied according to the 28-day feeding regime and the feed received immediately prior to testing, suggesting a colour contrast effect. The effect of visual experience with a variety of feed colours on neophobia was observed only when there was a marked contrast of colour with the feed received prior to testing which could be explained by an effect of memory on discrimination. When birds had been exposed to LC schedules, this visual experience resulted in the most significant decrease in neophobia. We conclude that changes in diet colour induce various levels of neophobia in turkeys which depend on the visual contrast between the new diet and that of the previous day, and the alternation rate of the visual experience. These results suggest that in production systems, the use of early visual experience with a variety of feed colours could reduce neophobia problems during change-over

Responses of laying hens to diets unbalalnced in energy and protein offered in sequential feeding

International audienc

The influence of sequential feeding with wheat on laying hens' feeding and pecking behaviour

International audienc