Maternal lactational effects on early weight gain. F1 and NON pups fostered on different lactational environments (obese F1 dam vs. lean NON dam) are significantly larger at postnatal day 18 if suckled on the obese F1 dam (P < 0.0001). Genotypic difference between F1 pups and NON pups is indicated by the fact that F1 pups will become significantly larger on the same lean NON lactational environment (P < 0.0001). Litter size was standardized to five to eight pups (mixed genders). Numbers of pups tested are shown in the bars. (BW) Body weight; (NON) nonobese nondiabetic.