The effects of dietary linoleic acid and hydrophilic antioxidants on basal, peak, and sustained metabolism in flight trained European Starlings

Dietary micronutrients have the ability to strongly influence animal physiology and ecology. For songbirds, dietary polyunsaturated fatty acids (PUFAs) and antioxidants are hypothesized to be particularly important micronutrients because of their influence on an individual's capacity for aerobic metabolism and recovery from extended bouts of exercise. However, the influence of specific fatty acids and hydrophilic antioxidants on whole-animal performance remain largely untested. We used diet manipulations to directly test the effects of dietary PUFA, specifically linoleic acid (18:2n6), and anthocyanins, a hydrophilic antioxidant, on basal metabolic rate (BMR), peak metabolic rate (PMR), and rates of fat catabolism, lean catabolism, and energy expenditure during sustained flight in a wind tunnel in European starlings (Sturnus vulgaris). BMR, PMR, energy expenditure, and fat metabolism decreased and lean catabolism increased over the course of the experiment in birds fed a high (32%) 18:2n6 diet, while birds fed a low (13%) 18:2n6 diet exhibited the reverse pattern. Additionally, energy expenditure, fat catabolism, and flight duration were all subject to diet-specific effects of whole-body fat content. Dietary antioxidants and diet-related differences in tissue fatty acid composition were not directly related to any measure of whole-animal performance. Together, these results suggest that the effect of dietary 18:2n6 on performance was most likely the result of the signaling properties of 18:2n6. This implies that dietary PUFA influence the energetic capabilities of songbirds, and could strongly influence songbird ecology, given their availability in terrestrial systems.

膳食微量营养素可对动物生理与生态产生显著调控作用。对于鸣禽而言，膳食多不饱和脂肪酸（polyunsaturated fatty acids, PUFAs）与抗氧化剂被认为是尤为关键的微量营养素，因其可影响个体的有氧代谢能力以及长时间运动后的恢复水平。然而，特定脂肪酸与亲水性抗氧化剂对整体动物机能的影响，在很大程度上仍未得到实验验证。我们通过膳食操控实验，直接检验了膳食多不饱和脂肪酸——即亚油酸（18:2n6）——以及亲水性抗氧化剂花色苷（anthocyanins），对欧椋鸟（Sturnus vulgaris）基础代谢率（basal metabolic rate, BMR）、峰值代谢率（peak metabolic rate, PMR），以及风洞持续飞行过程中的脂肪分解速率、瘦体重分解代谢率（lean catabolism）与能量消耗水平的影响。实验期间，饲喂高比例（32%）18:2n6膳食的欧椋鸟，其基础代谢率、峰值代谢率、能量消耗与脂肪代谢均出现下降，而瘦体重分解代谢率则有所上升；与之相对，饲喂低比例（13%）18:2n6膳食的个体则呈现出完全相反的变化趋势。此外，能量消耗、脂肪分解速率与飞行时长均受到机体整体脂肪含量的膳食特异性影响。膳食抗氧化剂水平与组织脂肪酸组成的膳食相关差异，与任何一项整体动物机能指标均无直接关联。综合上述结果，我们认为膳食18:2n6对动物机能的影响大概率源于其信号传导特性。这表明膳食多不饱和脂肪酸可影响鸣禽的能量代谢能力，鉴于其在陆地生态系统中的广泛存在，膳食多不饱和脂肪酸或可对鸣禽生态产生强烈调控作用。