Rauw W M, Knap P W, Gomez-Raya L, Varona L, Noguera J L
Area de Producció Animal, Centre UdL-IRTA, 177, 25198 Lleida, Spain.
J Anim Sci. 2003 Apr;81(4):939-44. doi: 10.2527/2003.814939x.
The present study investigated differences in the allocation patterns of body stores in lactating female mice from a line selected for high litter size at birth (S-line, average litter size of 20) and dams from a nonselected control line (C-line, average litter size of 10). Body weight, litter size, litter weight, and absolute and relative lipid and protein mass were measured at peak lactation (2 wk in lactation) and at weaning (3 wk in lactation). Body size in S-line females has been increased as a correlated effect of selection for high litter size at birth, allowing for larger litters and higher absolute milk production. However, these dams produce larger litters relative to their own body weight. At peak lactation, lipid and protein percentage did not differ between lines. At weaning, S-line females had a higher protein percentage (P < 0.001) and lower lipid percentage (P < 0.05) than C-line females. Apparently, S-line females produce more offspring but at a greater cost to their own metabolism. This process was insufficient to supply the offspring with adequate resources, resulting in reduced (P < 0.0001) pup development and increased (P < 0.0001) preweaning mortality rates.
本研究调查了出生时产仔数高的品系（S系，平均产仔数为20只）的泌乳雌性小鼠与非选择对照品系（C系，平均产仔数为10只）的母鼠在身体储存分配模式上的差异。在泌乳高峰期（泌乳2周）和断奶时（泌乳3周）测量体重、产仔数、窝重以及绝对和相对脂质和蛋白质质量。S系雌性小鼠的体型因出生时对高产仔数的选择而增大，这使得它们能够哺育更大的窝仔并产出更高的绝对奶量。然而，这些母鼠相对于自身体重哺育的窝仔更大。在泌乳高峰期，品系间的脂质和蛋白质百分比没有差异。断奶时，S系雌性小鼠的蛋白质百分比高于C系雌性小鼠（P < 0.001），脂质百分比低于C系雌性小鼠（P < 0.05）。显然，S系雌性小鼠产出的后代更多，但自身代谢付出的代价更大。这一过程不足以给后代提供充足的资源，导致幼崽发育减缓（P < 0.0001）和断奶前死亡率增加（P < 0.0001）。
