Intermittent Feeding in a Migratory Omnivore: Digestion and Body Composition of American Black Duck during Autumn

Abstract

Birds fast intermittently during weather disturbances and migration. We tested responses of black duck to lost feeding days during autumn mass gain. Nine adult males were fed a pelleted diet (1.5% fat, 15.8% protein, and 18.3% neutral detergent fiber) and caged indoors during September and October (12 h light; 17 degrees -24 degrees C) to measure balances over 14 d when fed ad lib. each day and fasted intermittently for 2 d wk(-1) (short fast) or 4 d wk(-1) (long fast). Body mass (1,081 g), body water content, and metabolizable intakes of energy and protein were maintained as daily intakes of dry matter increased to 1.65 (short fast) and 2.35 (long fast) times the unfasted level. Intermittent feeding reduced metabolizability of dry matter, energy, protein, and acid detergent fiber. Concentrations of Mn provided similar estimates of metabolizability to direct measures in unfasted birds but underestimated measures of birds on long fasts. Fasting regimes continued outdoors for 9 wk when temperatures declined to -9 degrees C. Birds on short fasts were heavier (1,373 vs. 1,241 g) and fatter (159 vs. 58 g) than those on long fasts, while body water (894 g) and protein (316 g) were similar between groups after 5 wk. Birds on long fasts subsequently gained mass when fed daily, but those on short fasts lost mass when fed each day. Omnivorous waterfowl combine ingestive and digestive flexibility with plasticity of body lipid to contend with uncertain food availability.

Intake, apparent digestibility, and digesta passage in leopard tortoises (Geochelone pardalis) fed a complete, extruded feed

“…Animals exhibited decreased apparent metabolizability of DM, energy, ADF, and cellulose when fasted, but NDF and hemicellulose metabolizability was not different [Barboza and Jorde, 2001]. In this study, apparent digestibility of cellulose was increased when animals were exposed to shorts fasts (i.e., when fed only 3 days per week), with no other differences between treatments.…”

“…In a study of American black ducks, Anas rubripes, animals were fed 7 days a week, and subsequently fasted either 2 or 4 consecutive days per week [Barboza and Jorde, 2001]. Animals exhibited decreased apparent metabolizability of DM, energy, ADF, and cellulose when fasted, but NDF and hemicellulose metabolizability was not different [Barboza and Jorde, 2001].…”

“…These differences might be related to the omnivorous feeding pattern of A. rubripes compared to the herbivorous feeding pattern of G. pardalis that may allow this species to more efficiently digest structural carbohydrate fractions [Bjorndal and Bolten, 1993]. Another factor is the relatively short retention time in birds, with rapid flow through the digestive tract, compared to the long observed R GIT in G. pardalis of 381.1 h [Barboza and Jorde, 2001]. …”

Anseriforme Husbandry and Management

“…Intermittent fasting is described in wild waterfowl and is often needed during migration [66]. In common with some other migrating species, hepatic steatosis is a main mechanism of energy storage in waterfowl and easily occurs with excessive carbohydrate ingestion (hence the development of the foie gras industry) [27].…”

“…Black ducks (Anas rubripes) have been studied after 4-day fasts (no food) and have lost weight and shown delayed egg production but otherwise underwent no significant adverse health effects [66]. Even young (10 and 20-day-old) Pekin ducklings have been studied with 5 days of calorie restriction (just enough to maintain relatively stable body mass).…”