Development, energetics and nutrition of captive Pacific Brant (Branta bernicla orientalis, Tougarinov)

Abstract

The development of young Pacific Brant (B. b. orientalis), energy relationships of young and adults and nutrition of brant utilizing eelgrass was studied in Fairbanks, Alaska on birds obtained from the breeding grounds of the Yukon-Kuskokwim Delta. Gosling growth rates were rapid with weight gain temporarily slowed by remige development. Feather growth curves were regular with secondaries and rectrices following the primary growth pattern closely; growth rate of primary 8 exceeded that of primary 9 during development. Subadult maximum and minimum yearly weights occurred in November and April, respectively. Thermoneutral winter oxygen rates were similar for both sexes; rates of males exceeded those of females. Winter metabolic rates of both sexes exceeded summer rates and were above predicted rates; summer rates were comparable to those predicted. Below the lower critical temperature, metabolism in creased linearly with decreasing ambient temperature in both seasons; slopes were not different. Metabolism below the critical temperature was significantly higher in winter than in summer. Body temperature averaged 40.9°C and was not labile from -50 to +30°C. Heart rate in creased linearly with decreasing ambient temperature below the critical temperature. Summer existence energy expenditure per bird and per gram body weight of females was greater than that of males. Gross activity pattern was highly random during the summer. Digestive efficiency did not change significantly with ambient temperature. Diets containing three levels of eelgrass fed to goslings were in effective in producing consistent or significant weight in creases which was attributed to unacceptability. Only control ration and 50% eelgrass produced positive feed efficiencies; positive efficiencies of utilization were obtained with control, 50% and 75% eelgrass diets. Digestive efficiency decreased significantly as the eelgrass in the diets in creased. Eelgrass nutrient constituent levels changed little over the collection period of 15 April to 19 November while caloric values decreased. Protein levels were consistently under dietary recommendations for geese.