Les conséquences de la dynamique de la digestion des aliments sur le métabolisme ruminal et les performances animales

National audienceResearch of the last decades have demonstrated that the kinetics of ruminal degradation of feeds vary largely in function of their nature and of the constituent. It can therefore be envisaged to take the opportunity of this variability to formulate compound feeds or mixed diets which are more and less rapidly degraded or more and less synchronized between the carbohydrates and proteins degradation rates in comparison with the microbe requirements. Experimental data related to the influence of the variations of these phenomena on ruminal digestion and zootechnical performances show that the effects are less important that could be a priori imagined. It is therefore necessary to explain that fact. It seems that numerous structures and phenomena of delay allow to smooth efficiently the dynamic variations of degradation processes between feeds or constituents. Several examples are evoked. For nitrogenous products smoothing phenomena particularly occur by a transient storage of peptides before microbial captation and nitrogenous recycling by protozoa and blood urea recycling. For energy nutrients, it seems that the most important transient storage of energy is in the form of polysaccharidic storage within the microbial cells. The dynamic approach of ruminal digestion also emphasizes that microbial growth rate is limited and less variable in short term, even if sufficient nutrients are available. Some comments and explanations are made on this aspect.Les travaux des dernières décennies ont montré que les cinétiques de dégradation ruminale des aliments variaient largement en fonction de leur nature et du constituant considéré. Il est donc envisageable de mettre à profit cette variabilité pour formuler des aliments composés, ou des régimes mixtes, plus ou moins rapidement dégradables ou plus ou moins bien équilibrés entre les flux des glucides et des protéines disponibles par rapport aux besoins des micro-organismes du rumen. Les résultats expérimentaux sur les effets des variations de ces phénomènes sur la digestion ruminale et sur les performances zootechniques indiquent que ces effets sont beaucoup moins importants que ce qui pouvait être envisagé a priori. Il est de ce fait nécessaire de rechercher des explications sur la capacité du rumen à « amortir » ces variations. Il semble que ce soit l’existence de nombreuses structures et phénomènes de délais qui permettent d’amortir efficacement les variations dynamiques des processus de dégradation entre aliments et constituants. Plusieurs exemples sont évoqués. Pour les constituants azotés, les phénomènes d’amortissement existent en particulier au niveau du stockage transitoire de molécules peptidiques avant captation par les cellules microbiennes et des recyclages d’azote par les protozoaires et le recyclage d’urée d’origine sanguine. Pour les constituants énergétiques, il semble que le stockage transitoire d’énergie le plus important soit le compartiment polysaccharidique des microbes. L’approche dynamique des phénomènes digestifs ruminaux indique en outre que la croissance microbienne est limitée et peu adaptable dans le court terme même si une quantité suffisante de nutriments est disponible. Quelques commentaires sont effectués sur cet aspect

Bases d'estimation des besoins énergétiques du porc en croissance

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Bases d'estimation des besoins énergétiques du porc en croissance

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Precision livestock feeding, principle and practice

Precision livestock farming (PLF) is proposed to the livestock industry as an essential tool to enhance sustainability and competitiveness.Precision livestock feeding is part of PLF and can have a great impact in livestock profitability due the ability of feeding pigs with diets tailored daily to their nutrient requirements.Precision livestock feeding can decrease livestock environmental impacts by optimising the use of dietary nutrients and animal nutrient utilisation efficiency which results in less nutrient excretion.Mathematical models developed for precision livestock feeding must be designed to operate in real-time using system measurements. These models are structurally different from traditional nutrition models.The success of PLF is dependent on the precision livestock feeding integration into the system, as well, the adaptability and training of the farmers to use PLF systems

Systèmes d'unité d'alimentation et lois de réponse du porc aux régimes alimentaires

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Etude et modélisation du phénomène de croissance compensatrice chez le porc

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Fasting heat production and metabolic body weight in growing animals

EAAP Scientific SeriesInternational audienceFasting heat production (FHP) of growing animals is indicative of their basal metabolic rate and it is proportional to the metabolic body weight (MBW), calculated as BW raised to a certain exponent. lt can be estimated from the analysis of the decreasing kinetic of total heat production during a rather short period of feed deprivation (about one day), as the horizontal asymptotic value corrected for zero physical activity. Specifie exponents should be used to calculate MBW in growing animals over the growing period; a compilation of our data suggest 0.60 in pigs, 0.70 in broilers, 0.75 in turkeys and 0.85 in calves. Therefore, they may differ from the classical 0.75 exponent more adapted to adults. From measurements conducted at different feeding levels, it appears that FHP varies by 0.13, 0.14 and 0.22 kJ per kJ variation in metabolisable energy intake prior to the fasting period, in turkeys, pigs and caIves, respectively. The size of the visceral organs and its evolution during growth would explain the difference between species and the effect offeeding level on basal metabolic rate. Within species, differences in FHP between breeds can be attributed to differences in visceral and protein mass, whereas differences between sexes were only significant when animals approach sexual maturity. Finally, high ambient temperature is associated with decreased FHP that can be mainly explained by the anorexie effect of heat stress. To conclude, variations in FHP arc indicative of variations in maintenance energy requiremcnts that should be taken into account in nutritional recommendations

Une inflammation modérée modifie la réponse de la croissance des porcelets à des apports croissants de tryptophane

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A Bayesian hierarchical model to integrate a mechanistic growth model in genomic prediction

International audienceGenomic prediction can improve the accuracy of estimated breeding values for traits driven by additive genetic effects within common settings but prediction of traits affected by non-additive genetic effects and GxE remains a challenge. Mechanistic growth models express growth performances in terms of nonlinear functional interactions between underlying latent traits and nutritional environmental effects. Assuming the latent traits are less affected by non-additive genetic effects and GxE, these models can capture certain non-additive genetic effects and GxE at the phenotype level and allow prediction at unobserved ages for longitudinal data, e.g. mature weight and mature feed intake. In this study, we developed a Bayesian hierarchical model to integrate a Gompertz model for body weight and feed intake into genomic prediction models for pigs. By predicting breeding values for biologically relevant underlying latent traits, these models have the potential to advance genetic improvement across populations and environments

Exploring the metabolic flexibility of the mammary gland of dairy cows through flux-balance analysis

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