2009 Volume 25 Issue 2 Pages 93-102
Resource cycling in animal production systems is important for promoting home-grown feeds and utilization of animal excreta in the systems. The cycling in the systems is needed to be evaluated as the numerical indicator of the cycling. Recently, Finn's cycling index developed in ecology has been introduced to the animal production systems as the indicator of element cycling in the systems. The index is applicable in the animal production systems and useful tool as an evaluation index. Therefore, the properties of the cycling index were confirmed for interpretation of the index in this study. Cycling index was defined as the ratio of internal cycling flow to the total system flow. It varies from 0 to 1, 0 meaning that there is no cycling and 1 meaning that all flow is cycled. Element cycling in dairy and beef production systems were evaluated using cycling index on the previous reports. The effects of model assumption on the cycling index were discussed. The difference in the indices between two types of input (import and import plus natural supply) was confirmed. Comparison of the cycling index in the two types of input indicated that cycling index was higher in the former type than in the latter type. Furthermore, change in cycling indices was discussed on the different number of components constructing the same system. The cycling index on the 2-5 component systems indicated no difference among the 2-4 component systems including the same flow path. This study provides useful information on the properties for the cycling index and in comparison of the index among case studies.