Bertrand Meda

A physiologically based pharmacokinetic model for chickens exposed to feed supplemented with monensin during their lifetime

We developed a flow-limited physiologically based pharmacokinetic model for residues of monensin in chickens and evaluated its predictive ability by comparing it with an external data set describing concentration decays after the end of treatment. One advantage of this model is that the values for most parameters (34 of 38) were taken directly from the literature or from field data (for growth and feed intake). Our model included growth (changes in body weight) to describe exposure throughout the life of the chicken. We carried out a local sensitivity analysis to evaluate the relative importance of model parameters on model outputs and revealed the predominant influence of 19 parameters (including three estimated ones): seven pharmacokinetic parameters, five physiological parameters and seven animal performance parameters. Our model estimated the relative bioavailability of monensin as feed additive at 3.9%, which is even lower than the absolute bioavailability in solution (29.91%). Our model can be used for extrapolations of farming conditions, such as monensin supplementation or building lighting programme (which may have a significant impact for short half-life molecules such as monensin). This validated PBPK model may also be useful for interspecies extrapolations or withdrawal period calculations for modified dosage regimens.

Prediction of nutrient flows with potential impacts on the environment in a rabbit farm: a modelling approach

To face the increasing demand for animal products throughout the world, livestock-farming systems have been intensified. This intensification has proven to be economically effective but is noted for its negative impact on the environment through the production of ammonia (NH3) and the greenhouse gases nitrous oxide (N2O) and methane. In this context, dynamic models are useful tools to evaluate the effects of farming practice on nutrient flows and losses to the environment. This paper presents the development of a model simulating the flows of nitrogen (N) and phosphorus (P) in a rabbit production farm. The model is comprised of two submodels. The first submodel simulates the number of animals in the farm (births, deaths, culling of does/fatteners) and their respective performances (growth, feed intake, milk production). The second one simulates the excretion of N and P for each animal category using a mass-balance approach between intake (feed and/or milk intake) and exports (body deposition, milk production, gestation). Specific emission factors are then applied to the excreted N amounts to estimate total N, NH3 and N2O losses in the housing unit and during manure storage. Methane emissions from enteric fermentations and manure are also estimated. A simulation example based on French technico-economic data illustrates how the model could be used to study the dynamics of animal populations within the system and of nutrient flows. Finally, there is a need for new knowledge (experimental data) to improve the model and help design more sustainable rabbit production systems by identifying best practices that minimise environmental impacts.

Reducing the CP content in broiler feeds: impact on animal performance, meat quality and nitrogen utilization

Reducing the dietary CP content is an efficient way to limit nitrogen excretion in broilers but, as reported in the literature, it often reduces performance, probably because of an inadequate provision in amino acids (AA). The aim of this study was to investigate the effect of decreasing the CP content in the diet on animal performance, meat quality and nitrogen utilization in growing-finishing broilers using an optimized dietary AA profile based on the ideal protein concept. Two experiments (1 and 2) were performed using 1-day-old PM3 Ross male broilers (1520 and 912 for experiments 1 and 2, respectively) using the minimum AA:Lys ratios proposed by Mack et al. with modifications for Thr and Arg. The digestible Thr (dThr): dLys ratio was increased from 63% to 68% and the dArg:dLys ratio was decreased from 112% to 108%. In experiment 1, the reduction of dietary CP from 19% to 15% (five treatments) did not alter feed intake or BW, but the feed conversion ratio was increased for the 16% and 15% CP diets (+2.4% and +3.6%, respectively), while in experiment 2 (three treatments: 19%, 17.5% and 16% CP) there was no effect of dietary CP on performance. In both experiments, dietary CP content did not affect breast meat yield. However, abdominal fat content (expressed as a percentage of BW) was increased by the decrease in CP content (up to +0.5 and +0.2 percentage point, in experiments 1 and 2, respectively). In experiment 2, meat quality traits responded to dietary CP content with a higher ultimate pH and lower lightness and drip loss values for the low CP diets. Nitrogen retention efficiency increased when reducing CP content in both experiments (+3.5 points/CP percentage point). The main consequence of this higher efficiency was a decrease in nitrogen excretion (−2.5 g N/kg BW gain) and volatilization (expressed as a percentage of excretion: −5 points/CP percentage point). In conclusion, this study demonstrates that with an adapted AA profile, it is possible to reduce dietary CP content to at least 17% in growing-finishing male broilers, without altering animal performance and meat quality. Such a feeding strategy could therefore help improving the sustainability of broiler production as it is an efficient way to reduce environmental burden associated with nitrogen excretion.

Effect of low incubation temperature and low ambient temperature until 21 days of age on performance and body temperature in fast-growing chickens

&NA; Thermal manipulation during embryogenesis was previously reported to decrease the occurrence of ascites and to potentially improve cold tolerance of broilers. The objective of our study was to explore the effects of the interaction of cold incubation temperatures and cool ambient temperatures until 21 d of age on performance and body temperature. Ross 308 eggs were incubated either under control conditions I0 (37.6°C) or with cyclic cold stimulations I1 (6 h/d at 36.6°C from d 10 to 18 of incubation) or with 2 cold stimulations I2 (30 min at 15°C) at d 18 and 19 of incubation. These treatments were followed by individual rearing and postnatal exposure to either standard rearing temperature T0 (from 33°C at hatching to 21°C at d 21) or continuously lower temperature T2 (from 28°C at hatching to 21°C at d 21) or exposure to cyclically lower temperature T1 (with circadian temperature oscillations). Treatments I1 and I2 did not significantly alter hatchability compared to control incubation (with 94.8, 95.1, and 92.3%, respectively), or hatching BW and overall chick quality. Hatching body temperature (Tb) was 0.5 and 0.3°C higher in I1 than in I0 and I2 groups, respectively (P = 0.007). A doubled occurrence of health problems was observed with T2 condition, regardless of incubation or sex. At d 3, BW was 2% lower with treatment I1 than with I0 and I2 and was 3% higher in T1 and T2 groups than in T0, but these effects disappeared with age. Group T2 presented a 5% higher feed intake than the control group T0 between 3 and 21 d of age (P = 0.025). Feed conversion ratio (FCR) was affected by experimental conditions (P < 0.001), with low FCR values obtained with I2 incubation in control or cyclically cold postnatal conditions. Maximal FCR values were observed in the continuously cold postnatal conditions, in males submitted to control incubation and in females submitted to I1 incubation, revealing sex‐dependent effects of the treatments on performance.

Photoacoustic Spectroscopy in Livestock Buildings: Interference Effects on Ammonia, Nitrous Oxide and Methane Concentrations

Most countries where the livestock sector has an important social and economical place would like to reduce their emissions of ammonia and greenhouse gases. However emission estimates per building and per year are usually observed or measured with uncertainties higher than the reduction targets. Therefore mitigation strategies and public fund efficiency should benefit from progress in measurement and modeling of emissions from livestock houses. The quantification of livestock house emissions requires accurate measurements of gas concentration gradients. Infrared photoacoustic is used since decades because of selectivity, reduced drift in calibration, existence of industrialized analyzers. But even if the infrared bands selected by optical filters are narrow, unexpected interferences between gases and cascade effect can induce overestimation or underestimation of gas concentration. In livestock houses, molecules emitted by animals, the feed, the manure, the heating or motor-driven equipments can interfere with measurements of CH4, N2O, NH3 and CO2 as it is not possible to compensate all the interferences. The aim of this study is to show how unexpected interferences in livestock houses can lead to either over/underestimation of NH3, N2O or CH4 concentration (e.g. for NH3, 12 instead of 2 mg/m3, and N2O, 3 instead of 1 mg/m3) and to discuss how to detect unexpected interferences and cascade effects and to decrease the uncertainty on concentration measurements.