0023-6152

AA00697606

24070

Unrefereed

0023-6152

AA00697606

The steady-state attainment of faecal excretion in ruminants given a new feed was predicted by the attainability coefficient calculated using the Blaxter’s compartmental model containing three parameters : length of preliminary period, outflow rate from rumen (k₁) and flow rate through hind-gut (k₂) of digesta. It was theoretically predicted that the faecal excretion approached a steady-state closer when the length of adaptation period was longer and/or the rate of digesta movement was higher. After the change of feed, the coefficient calculated for the faecal excretion derived from a previous feed showed a decrease to approach a zero-state closer when the longer period had passed and/or the digesta moved faster. Taking 28-day preliminary period led to the attainability coefficient higher than 0.99 irrespective of flow rate, meaning that a steady-state was attained for faecal excretion. Seven-day adaptation gave a value higher than 0.96 to the steady-state attainability provided both k₁ and k₂ were higher than 0.03. The application of the steady-state attainability to several published studies of various feeding conditions showed that the coefficient higher than 0.99 was given to almost all the cases in which 7-32 day adaptation was taken and flow rate was 0.014-0.085 for k₁ and 0.031-0.503 for k₂. The prediction was also applied to several other published studies with tropical forages where only kl was estimated to be 0.019-0.085 and 7-day adaptation gave a value higher than 0.94 to the steady-state attainability of most cases. It is suggested that the steady-state attainment of faecal excretion in ruminants may be predicted by the attainability coefficient calculated using the Blaxter’s model.