Grain legume fodders as ruminant feed in mixed crop-livestock systems in northern Ghana

Summary

Grain legumes are important crops in the mixed crop-livestock (MCL) systems in Africa because they provide food and cash for humans, fodder for animals and they improve soil fertility through biological nitrogen fixation. The residues of grain legumes, also known as grain legume fodders (GLFs), have better nutritional quality than cereal residues, such as maize and rice straw. Besides their function as livestock feed, GLFs supply fuel, construction material and mulch for soil improvement. However, knowledge about factors that drive the diversity of use of GLFs in different farming systems is limited. Therefore, the objective of this thesis was to understand the roles of grain legume fodders in mixed crop-livestock systems and identify options to improve their quality and utilisation by smallholders in northern Ghana. To achieve this objective, we conducted four multi-disciplinary studies. First, we assessed and described the variation in the use of GLFs to understand their impacts on MCL systems. Second, we evaluated and compared the effects of rhizobium inoculation and phosphorus fertilization on grain and fodder yield and fodder quality of the major grain legumes in two agro-ecological zones. Third, we evaluated the effects of storage conditions and duration on dry matter loss and nutritional quality of GLFs and to risk of aflatoxin formation in stored fodder. Lastly, we assessed the nutritional quality of stored GLFs using different quality assessment methods. Results show there is variation in the use of GLFs in the study regions in northern Ghana. For example, in Upper East region, most of the GLFs (87%) was stall-fed, whereas in Upper West region GLFs were for a considerable extent (61%), left on the field and used for mulching. In Northern region, both stall-feeding and grazing of GLFs was important. In our agronomic studies we found that rhizobium inoculation of cowpea seed, for example, increased grain yield by 44%, P-fertilization increased grain yield by 102% while the combination of P and inoculation increased grain yield by 123% compared to the control treatment where no input was applied. In the storage experiment, we found that dry matter loss during storage for 120 days was on average 24% across all storage conditions, 35% for the worst condition (tied in bundles and stored on roofs or tree-forks) and 14% for the best condition (sacks and in rooms). During storage, the CP content and OMD decreased, and the content of cell wall components increased. Aflatoxins were not detected in stored GLFs. Finally, in fodder quality assessment studies, all the four methods used (farmers’ perception, sheep preference, leaf-to-stem ratio and laboratory analyses) successfully discriminated GLF quality between crops. Only farmers and sheep could distinguish quality differences among storage conditions, whereas laboratory assessment methods could not. In general we concluded that with increasing importance of livestock in intensified MCL systems, GLFs become more important and more valuable for feeding, especially in the dry season. For this reason smallholder farmers can increased both grain and fodder yield of grain legumes concurrently through the use of rhizobium inoculation and P-fertilization. They can also reduce GLF nutritional quality and dry matter quantity loss by adopting appropriate fodder storage methods. The absence of aflatoxin in the groundnut fodder samples indicated that there is minimal risk of aflatoxin development when stored under dry conditions as in our study. Finally, farmers’ experience and local knowledge in feeding GLFs to livestock is valuable in determining the quality of GLFs and preference of their animals.