Effects of Lumbricus sp. Extract Supplementation Methods and Levels in Fermented Feed on Digestibility, Growth, Gut Emptying, Blood Glucose and Phagocytic Parameters of Milkfish, Chanos chanos (Forsskal, 1775)

Abstract

This study evaluated the effects of different Lumbricus sp. extract supplementation methods and levels in fermented feed on the digestibility, growth, gut emptying, blood glucose dynamics and phagocytic parameters of milkfish juveniles. Lumbricus sp. extract was applied either by spraying onto dried pellets or by mixing into the feed before pelleting at 0, 100, 200 and 300 mL kg^-1 feed. Experimental feeds were given to milkfish juveniles (17.80 ± 0.20 g) for 50 days in 1 m³ hapa cages in a pond with a water depth of approximately 70 cm at a daily feeding rate of 5% body weight. The 300 mL kg^-1 treatment, in both supplementation methods, improved feed digestibility, specific growth rate and digestive enzyme activity (cellulase, α-amylase and protease) compared with lower levels. Phagocytic activity and leukocyte count also increased, while blood glucose peaked and declined more rapidly in fish receiving the highest extract level. The 300 mL kg^-1 extract mixed into the feed before pelleting produced the fastest gut emptying, with complete emptying at the 5th postprandial hour. These findings indicate that Lumbricus sp. extract can be used as a functional additive in fermented milkfish feed, with 300 mL kg-1 as the most effective level under the present experimental conditions.