Hayssen V
Department of Biological Sciences, Smith College, Northampton, MA 01063.
J Dairy Sci. 1993 Oct;76(10):3213-33. doi: 10.3168/jds.S0022-0302(93)77659-6.
For 829 mammalian species, data on age at weaning or age at first solid food were analyzed with respect to body mass, phylogeny, habitat, diet, length of gestation, basal metabolism, and neonatal development. The primary influence on lactation length is female mass, but phylogenetic constraints are important. Thus, lactation can be characterized as short (earless seals and baleen whales), long (marsupials, bats, and primates), or average (remaining eutherians). Among average mammals, lagomorphs have short lactations. Lactation may have different functions, evolutionary constraints, and physiological control depending on whether young first eat solid food near weaning or well before it. First solid food eaten near weaning occurs in polytocous species with altricial young; in this case, lactation has a clear energetic role. In contrast, first solid food well before weaning is common for mammals with single, precocial offspring. For these species, the energetic and nutritional constraints on lactation may be less important than the benefits of maintaining contact between mother and young, such as reduced juvenile mortality and increased opportunities for learning social or foraging patterns. Thus, the age at first solid food relative to the age at weaning may indicate the function of lactation within the reproductive biology of a given mammal. Delayed development and implantation alter the timing of energetic investment during gestation, so too, the age at first solid food may alter or reflect the rate of energetic investment during lactation. Thus, the age at first solid food relative to the age at weaning may indicate the function of lactation within the reproductive biology of a given mammal. Testing these hypotheses will require data from diverse species on the nutritional and energetic value of milk before and after first solid food as well as on the mechanics and consequences of nursing or suckling during the course of lactation.
对于829种哺乳动物，我们分析了其断奶年龄或首次食用固体食物的年龄与体重、系统发育、栖息地、饮食、妊娠期长度、基础代谢和新生儿发育之间的关系。对哺乳期长度的主要影响因素是雌性体重，但系统发育限制也很重要。因此，哺乳期可分为短（无耳海豹和须鲸）、长（有袋类动物、蝙蝠和灵长类动物）或中等（其余真兽类）。在中等哺乳期的哺乳动物中，兔形目动物的哺乳期较短。根据幼崽是在断奶前后还是断奶前很久就开始食用固体食物，哺乳期可能具有不同的功能、进化限制和生理控制。在断奶前后食用固体食物的情况出现在产多仔且幼崽发育不全的物种中；在这种情况下，哺乳具有明显的能量供应作用。相比之下，对于产单仔且早熟的哺乳动物来说，在断奶前很久就开始食用固体食物的情况很常见。对于这些物种，哺乳在能量和营养方面的限制可能不如维持母婴接触的益处重要，比如降低幼崽死亡率以及增加学习社交或觅食模式的机会。因此，首次食用固体食物的年龄相对于断奶年龄可能表明了特定哺乳动物生殖生物学中哺乳的功能。发育延迟和着床会改变妊娠期能量投入的时间，同样，首次食用固体食物的年龄也可能改变或反映哺乳期的能量投入速率。因此，首次食用固体食物的年龄相对于断奶年龄可能表明了特定哺乳动物生殖生物学中哺乳的功能。要验证这些假设，需要来自不同物种的数据，包括首次食用固体食物前后乳汁的营养和能量价值，以及哺乳期内哺乳或吮乳的机制和后果。
