Kirkpatrick B W, Arias J A, Rutledge J J
University of Wisconsin, Madison 53706.
J Anim Sci. 1988 Jan;66(1):62-9. doi: 10.2527/jas1988.66162x.
Effects of prenatal and postnatal fraternity size (size of litter in which an animal develops prior to birth or is reared following birth) on long-term reproduction were studied by rearing 178 female ICR mice in standardized prenatal and postnatal fraternities. Three levels of prenatal and postnatal fraternity sizes were used in a 3 x 3 factorial experiment. Prenatal fraternity size was standardized by selectively terminating fetal development in pregnant females carrying at least 14 conceptuses. Prenatal fraternities were standardized to either 6, 10 or 14 fetuses, and postnatal fraternities were standardized by randomly assigning individuals to nurse litters of 5, 10 or 15 pups. Prenatal fraternity size negatively affected average pup weight at birth (P less than .05) but had little subsequent effect on growth or reproduction. Postnatal fraternity size negatively affected weight at weaning (P less than .01), with mice reared in smaller postnatal fraternities being heavier than those reared in larger fraternities. Following weaning, mice reared in smaller fraternities gained weight less rapidly (P less than .01) but still tended to be heavier at maturity (P = .11). Vaginal opening occurred at older ages in females reared in larger postnatal litters (P less than .01). An interval mating system was used to examine fraternity size effects on long-term reproduction. Females were exposed to males six times at 8-wk intervals with initial mating at 7 wk of age. Postnatal fraternity size and age at mating jointly affected litter size (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)
通过在标准化的产前和产后同胞规模中饲养178只雌性ICR小鼠，研究了产前和产后同胞规模（动物出生前发育或出生后饲养的窝仔大小）对长期繁殖的影响。在一个3×3析因实验中使用了三个水平的产前和产后同胞规模。产前同胞规模通过选择性终止至少怀有14个胚胎的怀孕雌性的胎儿发育来标准化。产前同胞规模被标准化为6、10或14个胎儿，产后同胞规模通过随机分配个体来哺育5、10或15只幼崽的窝仔来标准化。产前同胞规模对出生时的平均幼崽体重有负面影响（P小于0.05），但对随后的生长或繁殖影响很小。产后同胞规模对断奶时的体重有负面影响（P小于0.01），在较小产后同胞规模中饲养的小鼠比在较大同胞规模中饲养的小鼠更重。断奶后，在较小同胞规模中饲养的小鼠体重增加速度较慢（P小于0.01），但成熟时仍倾向于更重（P = 0.11）。在较大产后窝仔中饲养的雌性阴道开口年龄更大（P小于0.01）。采用间隔交配系统来检验同胞规模对长期繁殖的影响。雌性在7周龄时首次交配，此后每隔8周与雄性接触6次。产后同胞规模和交配年龄共同影响窝仔大小（P小于0.05）。（摘要截短至250字）
