Nadège Edouard

Manure management for greenhouse gas mitigation

Ongoing intensification and specialisation of livestock production lead to increasing volumes of manure to be managed, which are a source of the greenhouse gases (GHGs) methane (CH4) and nitrous oxide (N2O). Net emissions of CH4 and N2O result from a multitude of microbial activities in the manure environment. Their relative importance depends not only on manure composition and local management practices with respect to treatment, storage and field application, but also on ambient climatic conditions. The diversity of livestock production systems, and their associated manure management, is discussed on the basis of four regional cases (Sub-Saharan Africa, Southeast Asia, China and Europe) with increasing levels of intensification and priorities with respect to nutrient management and environmental regulation. GHG mitigation options for production systems based on solid and liquid manure management are then presented, and potentials for positive and negative interactions between pollutants, and between management practices, are discussed. The diversity of manure properties and environmental conditions necessitate a modelling approach for improving estimates of GHG emissions, and for predicting effects of management changes for GHG mitigation, and requirements for such a model are discussed. Finally, we briefly discuss drivers for, and barriers against, introduction of GHG mitigation measures for livestock production. There is no conflict between efforts to improve food and feed production, and efforts to reduce GHG emissions from manure management. Growth in livestock populations are projected to occur mainly in intensive production systems where, for this and other reasons, the largest potentials for GHG mitigation may be found.

NDIR Gas Sensor for Spatial Monitoring of Carbon Dioxide Concentrations in Naturally Ventilated Livestock Buildings.

The tracer gas ratio method, using CO2 as natural tracer, has been suggested as a pragmatic option to measure emissions from naturally ventilated (NV) barns without the need to directly estimate the ventilation rate. The aim of this research was to assess the performance of a low-cost Non-Dispersive Infra-Red (NDIR) sensor for intensive spatial field monitoring of CO2 concentrations in a NV dairy cow house. This was achieved by comparing NDIR sensors with two commonly applied methods, a Photo-Acoustic Spectroscope (PAS) Gas Monitor and an Open-Path laser (OP-laser). First, calibrations for the NDIR sensors were obtained in the laboratory. Then, the NDIR sensors were placed in a dairy cow barn for comparison with the PAS and OP-laser methods. The main conclusions were: (a) in order to represent the overall barn CO2 concentration of the dairy cow barn, the number of NDIR sensors to be accounted for average concentration calculation was dependent on barn length and on barn area occupation; and (b) the NDIR CO2 sensors are suitable for multi-point monitoring of CO2 concentrations in NV livestock barns, being a feasible alternative for the PAS and the OP-laser methods to monitor single-point or averaged spatial CO2 concentrations in livestock barns.

A meta-analysis of nutrient intake, feed efficiency and performance in cattle grazing on tropical grasslands

It is essential to quantify the potential of tropical grasslands to allow significant feed efficiency for grazing livestock in controlled conditions such as at pasture. We conducted a quantitative analysis of published studies reporting the experimental results of average daily gains (ADG) and diet characteristics obtained specifically under grazing conditions (17 publications and 41 experiments), which have been less studied compared with controlled conditions in stalls. The database was analyzed to determine the average and range of values obtained for ADG (g/kg BW), dry matter digestibility, intake (DMI) and digestible DMI (DDMI, g/kg BW) and feed conversion efficiencies (FCE), as well as to predict the response of these parameters to the main strategies investigated in the literature - that is, mainly the stocking rate (SR) and the concentrate intake (CI). The ADG reached 1.2 kg BW per day and was directly linked to DDMI (ADG=-1.63+0.42 DDMI -0.0084 DDMI2, n=90, r.m.s.e=0.584, R 2=0.93). The DDMI, which was representative of the nutrient input, was driven mainly by DMI rather than dry matter digestibility, whereas these two parameters did not correlate (r=0.068, P=0.56). The average global FCE (0.11 g ADG/g DDMI) showed a greater association with the metabolic FCE (0.17 g ADG/g DMI) than the digestive FCE (0.62). The CI (g DM/kg BW) increased ADG (ADG=2376+CI 56.1, n=16, r.m.s.e.=441, R 2=0.95). The SR expressed as kg BW/ha decreased the individual ADG by 1.19 g/kg BW per additional ton of BW/ha, whereas the global ADG calculated per ha increased by 0.57 per additional ton BW/ha. When the SR was expressed as kg BW/ton DM and per ha rather than as kg BW/ha, the impact on the individual ADG decreased by 0.18 or 0.86 g per additional ton BW/ha, depending on the initial BW of the cattle. These results provide a better view of the potential performance and feeding of cattle in tropical grasslands. The results provide an improved quantification of the relationships between diet and performance, as well as the overall quantitative impact of SR and supplementation.

How do horses graze pastures and affect the diversity of grassland ecosystems

In an agricultural context promoting the development of sustainable grazing systems, horses – whose numbers are increasing in Europe – have a significant role to play. However, compared to ruminants, the lack of data on how horses exploit pastures makes it difficult to propose management recommendations, despite evidence that grass can cover their nutritional requirements and that pasture management can be used to manipulate vegetation dynamics. In this review, we report recent insights into factors that affect the voluntary intake and feeding choices of grazing horses, and we specify the consequences of their diet selection on biodiversity in grassland ecosystems. Horses have a greater intake capacity on roughages than ruminants, which enables them to effectively control competitive grasses and maintain open areas in pastures. When facing variations in resource availability and quality, horses are able to adjust their foraging behaviour (daily grazing time, instantaneous intake rate, feeding site selection) in order to meet their nutritional requirements. How horse characteristics can affect their voluntary intake and feeding choices needs to be specified. The specific mode of grazing employed by horses maintains short lawns within a matrix of tall grass areas, which is known to promote plant and animal diversity, at least in the short term. Horses make less use of forbs and legumes than ruminants, and further studies are needed to determine whether this behaviour could benefit flowering plants and pollinating insects.

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.

Review and meta-analysis of the determinants of ruminant production in the tropics

Livestock production systems currently face a challenge because of increasing food demands and environmental issues. In this context, the multi-function of grazing systems (production, environmental and social/cultural objectives) is a way to achieve sustainable production. Over the last few decades, many studies have analysed plant-animal interactions in a temperate context and have resulted in a better understanding of the processes involved in plant-animal interactions. Up to now, no quantitative synthesis has ever been conducted under tropical conditions to assess the influence of various plant, animal and environmental factors on ruminant production. This would however be essential to highlight the contribution of these studies in order to propose models for the management of animals and grasslands in tropical environments. The aim of our work is to perform a meta-analysis of data from a literature review, in order to quantify the animal, vegetation and environmental factors, and their mutual interactions, explaining production levels variations in diverse climatic conditions and their relation with nutrition.