The Influence of the Length of Preliminary and Collection Periods on the Variation of Digestibilities in Goats

In order to get information on the appropriate length of preliminary and collection periods in a digestion trial, experiments with 4 Japanese Native Meat Type Goats were conducted for 90 days which consisted of three 30-day periods. The feces were collected at 24 hour interval for the last 63 days. The animals were fed ration 1 during the first and third periods and ration 2 during the second period. The levels of total digestible nutrients were 59% for ration 1 and 73% for ration 2, both calculated from the values in "Standard Tables of Feed Composition in Japan". The findings obtained were as follows: 1) The amounts of dry matter (DM) excreted and the contents of nitrogen (N), acid detergent fiber (ADF) and silica in the feces were affected by the change of the ration for 5-10 days. This suggested that a preliminary period of 5-10 days is necessary for a digestion trial. 2) Daily DM excretion in the feces varied much more than the contents of N, ADF and silica in DM, indicating that irregular daily fecal excretion influences to get accurate digestibility. 3) Digestibilities of DM calculated based on the composite feces of 3-, 5-, 7-day collection periods, respectively, indicated that the longer period tended to give smaller deviation. However, little improvement in accuracy of digestibility was obtained by the longer period. It was suggested, therefore, that 7 days are not always necessary for the collection period but the length depends on accuracy required in the experiment.