Cytoplasmic effects on selection response for increased growth rate in XXXX .

@entity19 @entity1017 @entity71050 @entity7840
To determine if cytoplasmic effects have contributed to long-term selection response for increased growth rate in @entity19 , reciprocal cross matings were made between an unselected control line (ICR) and a line (M16) derived from ICR by long-term selection for high postweaning @entity1017 from 3 to 6 wk of age. Embryos were recovered 2 to 4 d following mating and transferred to pseudopregnant F1 ( @entity7840 /2NCrlBR X C57BL/6NCrlBR) females. Thus, all embryos developed in similar uterine and postnatal maternal environments. A total of 122 @entity71050 ICR and 123 ICR X M16 @entity19 was produced, representing 19 litters from each cross. Litters were standardized at birth to five to seven pups. Litter weights at birth and 1 wk were recorded. Body weights at 2, 3, 4, 5 and 6 wk and @entity1017 from 3 to 6 wk were obtained. Weights of liver, kidneys, and sc and epididymal fat pads of males were obtained at 6 wk. Females were mated at 8 wk, and litter size at birth was recorded. Least-squares procedures were used to test for differences between reciprocal crosses for all traits. Body weight at 4 wk was higher (P less than .05) for @entity19 with ICR cytoplasm. No other significant differences were detected. There was no evidence that cytoplasmic effects influenced direct or correlated responses to long-term selection for increased postweaning @entity1017 .
