Methodological challenges in evaluating impact of crop-livestock interventions

Assessing the impact of interventions—technologies, strategies, techniques, policies— aimed at improving the overall productivity of crop–livestock systems is challenging. It is similar to the challenge faced by those attempting to measure the impact of integrated natural resource management (INRM) strategies. However, INRM strategies do not necessarily involve livestock, which further complicate such assessments. When higherquality, more-digestible feed is introduced into the system, or an animal health intervention is adopted that lowers mortality rates, it is not actually the increase in feed efficiency or a healthier animal that donors or research managers want to see—what interests them is the impact on people. Thus it is important to translate the findings of biophysical scientists—on, for example, the rates of feed utilisation or improved soil fertility—into measures that are more meaningful to a broader audience. This paper summarises approaches that have been used by the International Livestock Research Institute (ILRI) in recent years to do this, using the example of improved dual-purpose cowpea research. It discusses the strengths and weaknesses of the methods used, and presents some new approaches that have been initiated and will be pursued in the future to overcome some of the weaknesses of the analyses to date.