Kirkpatrick B W, Rutledge J J
University of Wisconsin, Madison 53706.
J Anim Sci. 1988 Oct;66(10):2530-7. doi: 10.2527/jas1988.66102530x.
Hypotheses of a negative association between fraternity size (size of litter in which an individual develops prior to birth or is reared following birth) and ovulation rate or litter size were tested by examining reproduction of females born or reared in varying prenatal and postnatal fraternities. Gifts were randomly assigned to develop prenatally and be reared postnatal in small or large fraternities. Dams of experimental animals were randomly assigned to one of two prenatal fraternity size treatments, either unilateral oviductal ligation (to bear a small prenatal litter) or no ligation (to bear a normal prenatal litter). Whereas this did result in differences (P less than .01) in litter size at birth (small = 6.2 +/- .4 vs large = 9.6 +/- .9), there was considerable overlap in observed litter sizes between ligated and nonligated dams. Consequently, effects of prenatal fraternity size were examined by regression. Distinct differences in postnatal fraternity size were created by randomly assigning piglets to small (5 piglets) or large (10 piglets) postnatal fraternities within 24 h of birth. Differences in postnatal fraternity size were maintained through weaning at 3 wk (small = 4.9 +/- .1 vs large = 9.4 +/- .2). Weights at birth (regression of birth weight on prenatal fraternity size = -.07 +/- .02, P less than .01) and weaning (small = 6.09 +/- .15 vs large = 5.46 +/- .17 kg, P less than .01) were heavier for gilts from small prenatal and postnatal fraternities, respectively, compared with gilts from large fraternities. Effects of prenatal and postnatal size on BW did not persist following weaning (P greater than .20).
通过研究在不同产前和产后同胞群体中出生或饲养的雌性动物的繁殖情况，对同胞群体大小（个体出生前发育或出生后饲养的同窝仔畜数量）与排卵率或窝仔数之间呈负相关的假设进行了检验。将仔猪随机分配，使其在小或大的同胞群体中进行产前发育和产后饲养。实验动物的母畜被随机分配到两种产前同胞群体大小处理之一，即单侧输卵管结扎（产小的产前窝仔）或不结扎（产正常大小的产前窝仔）。虽然这确实导致了出生时窝仔数的差异（P小于0.01）（小窝 = 6.2±0.4 只，大窝 = 9.6±0.9 只），但结扎和未结扎母畜的观察窝仔数有相当大的重叠。因此，通过回归分析来研究产前同胞群体大小的影响。通过在出生后24小时内将仔猪随机分配到小（5头仔猪）或大（10头仔猪）的产后同胞群体中，创造出产后同胞群体大小的明显差异。产后同胞群体大小的差异一直保持到3周龄断奶时（小窝 = 4.9±0.1 头，大窝 = 9.4±0.2 头）。与来自大同胞群体的后备母猪相比，来自小产前和产后同胞群体的后备母猪出生时体重（出生体重对产前同胞群体大小的回归系数 = -0.07±0.02，P小于0.01）和断奶时体重（小窝 = 6.09±0.15 千克，大窝 = 5.46±0.17 千克，P小于0.01）分别更重。断奶后，产前和产后群体大小对体重的影响不再持续（P大于0.20）。
