Updated and revised by Richard Kersbergen, Extension Professor and Cooperating Professor in Animal and Veterinary Sciences. Originally Developed by Mahmoud El-Begearmi, Extension Professor. Reviewed by Beth Calder, Extension Professor and Assistant Professor of Food Science; and David Handley, Extension Professor and Cooperating Professor of Horticulture. For information about UMaine Extension programs and resources, visit extension.umaine.edu.