Estimation of enteric methane emissions in Sudanese Fulani zebu according to feeding strategies in West Africa

Résumé

<div><p>Livestock in Sub-Saharan Africa (SSA) is attracting great attention not only because of its contribution to food security but also because of its emissions of greenhouse gases (GHG). The GHG most emitted by livestock in this region is enteric methane (eCH4). This thesis project aims to perform in vivo measurements of eCH4 emissions in Sudanese Fulani zebu based on current farmers' feeding practices. After a general introduction, which sets the context of the study and explains the research objectives, Chapter 1 reviews the different methods for measuring, predicting and mitigating eCH4 in tropical areas, and reports the GreenFeed® system, the respiratory chamber, the sulfur hexafluoride, and the methane laser detector, as the most commonly used ones.</p><p>Apart from the three Tiers of the IPCC (Intergovernemental Panel on Climate Change) and the Global Livestock Environmental Assessment Model (GLEAM), twenty-seven (27) empirical prediction models have been used in SSA to estimate eCH4. Furthermore, different strategies for eCH4 mitigation, including nutritional and genetic strategies, methanogenic immunization, and management of production systems are detailed in this chapter. While eCH4 emissions by ruminants are influenced by both the quantity and quality of feed intake, these two parameters are subject to seasonal variation along the rangelands, which are the main source of ruminant feed in the extensive pastoral and agropastoral systems of West Africa. Chapter 2 reports the results of an experiment conducted to to test whether or not this seasonality in fodder availability and supply has an impact on feed intake levels and consequently on eCH4 in ruminants under the current farmers' feeding practices. During the three main seasons of the year (wet, cold dry and hot dry seasons) animals were fed rangeland fodder, considering the variation in the quantity of the rangeland fodder available in each season. Significant seasonal variations in dry matter intake (DMI), apparent digestibility, and eCH4 emissions were observed. The and L. leucocephala respectively. The multiplication of fodder banks of these tree legumes is a crucial step to make these resources more available to livestock farmers in SSA. Furthermore, cultivated forages are now being popularized among ruminant farmers to improve animal feeding conditions.</p><p>But the impact of the consumption of these forages in terms of eCH4 emissions remains little known in SSA. The objective of the study conducted in Chapter 5 is to compare the eCH4 emissions induced by three main cultivated grasses, namely Andropogon gayanus, Brachiaria ruziziensis and Panicum maximum harvested at maturity stage, to those induced by rangeland fodder in the hot dry season. The type of forage influenced the chemical component, intake and digestibility of the forages. However, the eCH4 emissions induced by these mature forages were not different from those caused by rangeland fodder.</p><p>However, P. maximum may be preferred over other forages given its low eCH4 yield per unit of digestible matter intake. Measuring eCH4 emissions induced by these forages at different growth stages will make it possible to specify their optimum stage of use in the context of environmental sustainability.</p><p>It is concluded from this study that the eCH4 emissions from zebu cattle are influenced by seasonal variations in rangeland fodder quality, intake, digestibility, the supplementation with crop coproducts, and the type of forages. In the future, it would be interesting to carry out such work directly on rangeland in order to improve seasonal emissions, to test the other resources used by farmers, to broaden the spectrum of potential resources for mitigating eCH4, and to popularize these results in a real environment in order to facilitate joint efforts in the fight against climate change.</p></div>

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