A longitudinal study of the postnatal maternal effect on the craniofacial growth of mouse offspring by cross-nursing.

A cross-nursing experiment was conducted to examine the nursing dam strain effect on the postnatal growth of a newborn mouse offspring by simultaneously using larger DDD strain mice and smaller C57BL strain ones. A periodical cephalometric observation of the postnatal craniofacial growth of the offspring was longitudinally made from birth up to the 100th day of life in addition to measuring the offspring weight. According to multivariate statistical analyses, the following results were obtained: 1) The mean body weight of the DDD offspring cross-nursed by the C57BL dam was significantly lighter than that of the DDD offspring self-nursed by the DDD dam throughout the whole experimental period except at birth and on the 100th day. 2) The mean body weight of the C57BL offspring cross-nursed by the DDD dam was significantly heavier than that of the C57BL offspring self-nursed by the C57BL dam from the 10th day up to the 30th day. 3) There was a significant positive relationship between the offspring weight and the offspring craniofacial size throughout the entire experimental period in the C57BL offspring and from the 10th day up to the 40th day in the DDD offspring. 4) The nursing dam strain effect on the craniofacial size of the DDD offspring was also significant on the 30th, 60th, 80th, and 100th days. The adjusted craniofacial size of the DDD offspring cross-nursed by the C57BL dam was significantly smaller than that of the DDD offspring self-nursed by the DDD dam on the 30th, 60th, 80th, and 100th days. 5) The nursing dam strain effect on the craniofacial size of the C57BL offspring was not significant throughout the whole experimental period. The adjusted craniofacial size of the C57BL offspring cross-nursed by the DDD dam was almost the same as that of the C57BL offspring self-nursed by the C57BL dam throughout the whole experimental period. 6) The fat content of the DDD dam tended to be higher than that of the C57BL dam and the interstrain difference was closed to a significant level (P = 0.06) on the 20th day. The moisture content of the DDD dam tended to be lower than that of the C57BL dam and the interstrain difference was also significant on the 7th day (P < 0.001). Based on these findings, it can thus be concluded that the nursing dam strain effect played an important role in the postnatal somatic growth of the DDD and the C57BL offspring and the craniofacial growth and the DDD offspring.