1. 1 Center for Applied Research on the Environment and Sustainability , The American University in Cairo , Cairo , Egypt
2. 2 Department of Animal Production, Faculty of Agriculture , Kafrelsheikh University , Kafrelsheikh , Egypt
3. 3 Department of Animal Production , Ghent University , Ghent , Belgium
4. 4 Department of Engineering Hydrology , The RWTH Aachen University , Aachen , Germany