Relationships among food ingestion, food digestion and body weight gain in the silkworm larvae, Bombyx mori, under the restricted feeding by indexes

Abstract

The present study was undertaken to investigate the relationships among food ingestion, food digestion and body weight gain in the 5th-instar larvae of the three races under the restricted feeding by several indexes. An amount of mulberry leaves supplied was determined by multiplying body weight by indexes from 0.1 to 0.8, and this mulberry feeding was done twice a day. In each feed index of the three races, daily changes of amounts of food ingested and of food digested were closely correlated with those of body weight during feeding period of the 5th-instar. The approximate digestibility (A.D.) remained more or less constant levels from the first to middle day of the instar, declined gradually during the latter days, and then fell sharply at just before the spinning. The differences of the A.D. among the feed indexes were not statistically significant (P>.05). The efficiency with which digested food was converted to body substances (E.C.D.) was decreased with larval growth in the every feed indexes. The accelerations of decreased speed of the E. C. D. with larval growth were, however, not significant (P>.05) among the feed indexes. The smaller feed index increased the levels of E. C. D., There was a significant difference (P<.01) of the E. C. D. levels of the early stage of the 5th-instar among the feed indexes. It was, therefore, found that the restricted feeding by the indexes influenced on the E. C. D., but not on the A. D.. The feed efficiency calculated from A.D.×E.C.D. or gain/feed was alike to the E. C. D. in the daily changes and in the properties among the feed indexes.