Feed input and excreta collection time in metabolisable energy assays for ducks

Abstract

Three experiments were conducted to determine the optimal feed input and excreta collection time by a bioassay of dietary true metabolisable energy (<i>TME</i>) for ducks. In experiment 1 and experiment 2, the time for the unabsorbed feed passage through the alimentary canal was determined by measuring the DM and energy of excreta and feed residues in the alimentary canal at different periods. In experiment 3, the feed input of force-feeding was studied and a total of 70 mature Pekin drakes were allotted to 7 groups, each group containing 10 birds. After fasting for 36 h, one group served as a negative control to measure metabolic faecal energy plus endogenous urinary energy and the drakes of the other 6 groups were force-fed pelleted feed 30 g, 50 g, 70 g, 90 g, 110 g, and 150 g per bird, respectively. Energy excretion of the periods of 16–28 h after force-feeding was significantly higher than that of the periods after 32 h, and the total energy excretion of the periods after 32 h (<i>P</i> < 0.05). When the feed input increased from 30 g to 70 g, the value of <i>TME</i> was constant (<i>P</i> > 0.05). Metabolisable energy decreased significantly with an increase in feed input when the feed input was higher than 70 g (<i>P</i> < 0.05). It was concluded that the optimal time of feed withdrawal before tube-feeding and during excreta collection would be 32–36 h. The optimal feed input was 50 g to 70 g per drake.