Indices of Fat and Protein for Ring-Necked Ducks

Abstract

Indices of ash-free lean dry body weight and body fat using easily obtained tissue weights and structural measurements were developed for ring-necked ducks (Aythya collaris) collected throughout the annual cycle. The linear regression model incorporating eviscerated carcass weight, wet leg and breast muscle weights, and bill length measurements explained 81% of the variation in ash-free lean dry weight. Wet weights of the abdominal (omental) fat and shared skin tissues accounted for 96% of the variation in body fat. Comparison of direct and indirect measures of nutrient composition confirmed that indices may be used to accurately estimate body protein and fat content of ring-necked ducks. J. WILDL. MANAGE. 50(2):209-211 The ability to assess nutrient reserve levels in waterfowl is important in understanding their strategies for survival and reproduction and in managing habitats to meet changing waterfowl needs. Laboratory assays commonly used to determine fat and protein content of animal tissues are expensive and time intensive. Indices of fat and protein using easily obtained tissue weights and morphological measures have been developed for several waterfowl species to circumvent costly laboratory analyses (Woodall 1978, Bailey 1979, Wishart 1979, Campbell and Leatherland 1980, Chappell and Titman 1983, Thomas et al. 1983). The objective of our study was to develop simple, accurate methods for estimating fat and protein content of ringnecked ducks. We are grateful to W. A. Chappell, M. W. Weller, and R. A. Wishart for their helpful comments on earlier drafts of the manuscript. Financial support was provided by the North Am. Wildl. Found. through the Delta Waterfowl and Wetland Res. Stn., the Univ. Minnesota (Dep. Fish. and Wildl., Comput. Cent., Agric. Exp. Stn., and Graduate School), Minn. Dep. Nat. Resour., and the Minn. Waterfowl