Mothers of the Atlantic grey seal, Halichoerus grypus, lactate for about 20 days, during which they do not feed and may have no access to water. Following weaning, they depart to sea leaving their pups unattended and unfed for up to another 40 days. We are interested in how this lactation strategy supports the pups’ rapid growth and development while also preparing them for their long fast before independently going to sea. We report a broad spectrum metabolomic analysis of whole milks of these seals that reveals continuous changes in key metabolites from birth to weaning. Certain components exhibit abbreviated appearances at the onset of lactation, followed by continuous rises or falls in others until weaning. Riboflavin/Vitamin B2, hormone-related sterol sulfates, lactose, and complex oligosaccharides all appear in milk briefly after birth then disappear. Lipids associated with cellular signaling and brain development occur at highest levels shortly after birth, then diminish. In contrast, other lipids and Vitamin B6/pyridoxine steadily increase as weaning approaches. Overall, these findings may indicate an early transition from carbohydrate to fat-based energy metabolism and establishment of gut microbiomes in pups, followed by provisioning for post-weaning development and fasting.

中文翻译：

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大西洋灰海豹乳显示幼崽从出生到断奶的关键代谢物和代谢转变指标的持续变化

大西洋灰海豹的母亲 Halichoerus grypus 会分泌乳酸约 20 天，在此期间它们不进食，也可能无法获得水。断奶后，它们会出海，让幼崽无人看管和喂食长达 40 天。我们感兴趣的是这种哺乳策略如何支持幼崽的快速生长和发育，同时也为它们在独立出海之前的长期禁食做好准备。我们报告了对这些海豹全脂奶的广谱代谢组学分析，揭示了从出生到断奶的关键代谢物的持续变化。某些成分在泌乳开始时表现出短暂的外观，然后在其他成分中持续上升或下降，直到断奶。核黄素/维生素 B2、激素相关甾醇硫酸盐、乳糖、和复杂的低聚糖都在出生后短暂地出现在牛奶中然后消失。与细胞信号传导和大脑发育相关的脂质在出生后不久以最高水平出现，然后减少。相比之下，其他脂质和维生素 B6/吡哆醇随着断奶的临近而稳步增加。总体而言，这些发现可能表明幼崽早期从碳水化合物向以脂肪为基础的能量代谢转变并建立肠道微生物群，随后为断奶后发育和禁食做好准备。