CORRELATED RESPONSES TO SELECTION FOR POSTWEANING GAIN IN THE RAT

摘要: Evidence for correlated responses to selection was investigated in lines of rats selected 13 generations high (U line) and low (D 3–9-week gain comparison with random-bred control (R C lines). The increase the U shown be due largely an 9-week weight, although 3-week weight also increased these lines. In D lines, where a marked decrease observed, this found large no detectable change weight. average 2-week litter measure lactational performance dam, significantly greater than Selection led changes size at birth same direction as that selection. This resulted higher number alive 2 9 weeks age percentage mated females pupping were similar but lower random bred providing evidence reduction "fitness" Carcass composition studied all 11th generation composition, terms water, fat, ash protein, R had more water less fat or line. carcass It is suggested are potentially useful animals investigate further developmental physiological mechanisms which growth.