Tropentag, September 10 - 12, 2025, Bonn "Reconciling land system changes with planetary health"

Effects of water regimes and defoliation on herbaceous forage yield and nutritional quality in the Sahel

¹Cheikh Anta Diop University of Dakar (UCAD), Senegal
²Senegalese Agricultural Research Inst., Centre de recherches Zootechniques de Dahra, Senegal
³Pastoralism and Drylands Pole (PPZS), Senegal
⁴Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), UMR SELMET, France

Abstract

In the Sahel, the main economic activity is livestock, which depends on grassland production and dynamics. However, the feed resources are predicted to be affected by increased extreme climatic events, human exploitation, and their impact needs to be evaluated. This study aimed to understand the effects of variable rainfall patterns and defoliation on herbaceous vegetation in the Sahel region. Digestible crude protein (DCP), feed unit for meat production (UFV) and in-feed unit for lactation (UFL) were measured in forage samples collected under a rainout shelter experiment conducted in the natural rangeland in Dahra, Senegal during the rainy season 2022. The experiment consisted of a factorial combination of four water regimes (WR) with or without defoliation and one control (C, natural rainfall, 306 mm), replicated twice. The WR refers to two wet treatments that received more than the natural rainfall (differing by water application interval, W1, W2, 562 mm) and two dry treatments that received less than the natural rainfall (differing by periods of break D1, D2, 200 mm). Linear mixed models were used to compare treatments. The results showed that the Dry Matter (DM) of wet treatments (W1=638±98 g/m², W2= 679 ±98 g/m²) were significantly higher than dry and control treatments (C=315±133 g/m², D1=334±98 g/m², D2=276±98 g/m²) and no difference between defoliation and no defoliation treatment(p=0.06). DCP, UFV, UFL were not influenced by either WR or defoliation (p > 0.05) indicating that forage quality was the same between treatments. However, forage quality was sufficient to meet livestock needs (47±4≤DCP≤58±9 g/kg of DM 0.4±0≤UFL≤0.5±0 by kg of DM, 0.4±0≤UFV≤0.5±0 by kg of DM). The primary effect observed was that the water regime influenced the quantity of forage, but not its quality, which is related to the phenological stage. These results might be helpful for the management of semi-arid and arid grassland livestock systems.

Keywords: Forage quality, forage quantity, grazing, livestock systems, pastoralism, rangeland aboveground biomass, sahel, Senegal

Contact Address: Adjoua Ange-Jokebed N'Goran, Cheikh Anta Diop University of Dakar (UCAD), Dakar, Senegal, e-mail: jokebedngorangmail.com