Avian diet quality is typically measured using true metabolizable energy (TME_N), which is a measure of assimilable energy of food items accounting for innate endogenous losses. Originally developed for use in the poultry industry, TME_N methods have been adapted to determine the value of natural foods consumed by waterfowl to parameterize bioenergetics models for conservation planning. Because there is little knowledge of the variation in TME_N estimates among food items and waterfowl species, we investigated TME_N of 6 common species of submersed aquatic vegetation for mallards (Anas platyrhynchos; i.e., a diet generalist) and gadwall (Mareca strepera; i.e., a diet specialist) in the midwestern United States during autumn 2015–2017. We precision fed and collected excreta from ducks using standard bioassays to estimate TME_N. Mallards had slightly greater TME_N than gadwall, but there was considerable variation in TME_N among vegetation species, duck species, and individuals within each species. True metabolizable energy (±SE; kcal/g[dry]) for mallards was greatest for Canadian waterweed (Elodea canadensis; 1.66 ± 0.26), followed by coontail (Ceratophyllum demersum; 1.51 ± 0.28), southern naiad (Najas guadalupensis; 1.37 ± 0.39), sago pondweed (Stuckenia pectinata; 0.50 ± 0.22), wild celery (Vallisneria americana; 0.05 ± 0.42), and Eurasian watermilfoil (Myriophyllum spicatum; –0.13 ± 0.42). Mean TME_N for gadwall was greatest for Eurasian watermilfoil (0.77 ± 0.32), followed by Canadian waterweed (0.70 ± 0.31), coontail (0.55 ± 0.28), southern naiad (–0.61 ± 0.34), wild celery (–0.98 ± 0.39), and sago pondweed (–1.07 ± 0.33). Generally, TME_N for most vegetation species was less than agricultural grains, but it was similar to ranges reported for seeds of naturally occurring hydrophytic vegetation and aquatic macroinvertebrates. We recommend that conservation planners incorporate species‐specific TME_N estimates in bioenergetics models and that future researchers improve TME_N assays for wild waterfowl following our recommendations. © 2020 The Wildlife Society.

中文翻译：

---

水生植被和鸭子之间真实可代谢能量的变化

禽类饮食质量通常使用真正的代谢能（TME _N）来衡量，这是衡量食品固有天生内源性损失的同化能的量度。TME _N方法最初是为家禽业而开发的，已被修改为确定水禽消耗的天然食品的价值，以参数化用于保护规划的生物能模型。因为在TME的变化了解甚少_ň估计食品和水禽物种中，我们调查TME _ň的沉水植被的6种常见的野鸭（绿头鸭，即饮食通才）和赤膀鸭（Mareca strepera; （例如，饮食专家）在2015年至2017年秋季的美国中西部。我们精度供给和使用标准生物测定法来估计TME鸭收集的排泄物_Ñ。绿头鸭的TME _N略高于野鸭，但是TME _N在植被物种，鸭物种和每个物种中的个体之间存在相当大的差异。绿头野鸭的真实代谢能（±SE; kcal / g [干]）以加拿大水草（Elodea canadensis ; 1.66±0.26）为最大，其次是鸡尾草（Ceratophyllum demersum ; 1.51±0.28），南部是naiad（Najas guadalupensis ; 1.37± 0.39），西米藜（Stuckenia pectinata ; 0.50±0.22），野生芹菜（美国苦草; 0.05±0.42）和欧亚水乳白（Myriophyllum spicatum； –0.13±0.42）。g壁的平均TME _N在欧亚水草（0.77±0.32）中最大，其次是加拿大水草（0.70±0.31），鸡尾草（0.55±0.28），南部奈德（–0.61±0.34），野生芹菜（–0.98±0.39）和西米草（–1.07±0.33）。通常，大多数植被物种的TME _N均小于农业谷物，但与报道的天然水生植物和水生无脊椎动物种子的范围相似。我们建议保护规划者将物种特定的TME _N估算值纳入生物能学模型，并建议未来的研究人员改进TME _N按照我们的建议进行野生水禽的检测。©2020野生动物协会。