Peak energy turnover in lactating European hares: the role of fat reserves.
Peak energy turnover in lactating European hares: the role of fat reserves.
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DOI：
10.1242/jeb.022640
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发表时间：
2009-01
期刊：
影响因子：
--
通讯作者：
Ruf T
中科院分区：
文献类型：
--
作者：
Valencak TG;Tataruch F;Ruf T
中欧的欧洲野兔（Lepus europaeus）繁殖的能量成本很高，主要是由于早熟，快速生长的年轻人主要依赖于富含能量的牛奶。因此，在这种气候下，野兔在冬季积累大量脂肪，然后在春季至秋季的繁殖季节逐渐耗尽。我们假设，在繁殖季节减少女性的脂肪储存可能会影响资源分配，峰值能量同化在哺乳期，或在后代的总投资。因此，我们测量的能量摄入量，牛奶质量和牛奶生产在整个哺乳期在春季，夏季和秋季，在女性饲养（大小操纵）窝与三个年轻的每个，在自然光周期，但在缓冲的环境温度在我们的设施。在整个繁殖季节的过程中，牛奶产量保持不变，但牛奶的脂肪含量下降。因此，总能量转移到年轻的显着下降。通过使用十一烷酸作为体内脂肪动员的示踪剂，我们能够表明乳脂部分来源于母体脂肪储存，特别是在春季。哺乳期女性的峰值持续能量同化率显着较高，在秋季，由于食物摄入量的增加。我们的结论是，脂肪商店允许女性野兔下调能量摄入量和支出早在繁殖季节，而晚繁殖迫使他们达到峰值能量摄入水平。因此，我们认为，在野兔，在哺乳期的能量周转高峰与脂肪储备的可用性。对持续代谢率的限制是对生殖投资的可变约束。可能有一个权衡精力成本的母亲养育早与晚窝在一年中。
European hares (Lepus europaeus) in central Europe have high energetic costs of reproduction, mainly due to precocial, rapidly growing young that rely largely on energy rich milk. Thus, hares in this climate build up large fat stores during winter which are then gradually depleted during the spring to autumn breeding season. We hypothesized that diminishing fat stores of females over the breeding season may affect resource allocation, peak energy assimilation during lactation, or the total investment in offspring. Therefore, we measured energy intake, milk quality and milk production throughout lactation in spring, summer and autumn, in females raising (size-manipulated) litters with three young each, under natural photoperiod but at buffered ambient temperatures inside our facility. Over the course of the breeding season the amount of milk production remained constant but fat content of the milk decreased. Hence, total energy transfer to young decreased significantly in autumn. By using undecanoic acid as a tracer of body fat mobilization we were able to show that milk fat partially originated from maternal fat stores particularly in spring. Peak sustained energy assimilation rates of lactating females were significantly higher in autumn, due to increased rates of food intake. We conclude that fat stores allow female hares to downregulate energy intake and expenditure early in the breeding season whereas late breeding forces them to reach peak energy intake levels. Accordingly, we suggest that in hares, peak energy turnover during lactation varies with the availability of fat reserves. Limits to sustained metabolic rate serve as variable constraints on reproductive investment. There may be a trade-off in energetic costs to mothers rearing early vs. late litters in the year.
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