Abstract
The contribution of diet and surgery to the brain weight deficits observed in artificially reared rats was investigated. Four day old Long Evans rat pups were assigned to an artificially reared (AR) or mother reared (MR) group. AR pups were encannulated and fed either rat milk (ARβMOM) or replacement formula (ARβMES). MR. pups received a sham encannulation (MRβSHAM) or no surgery (MRβCONT) before being returned to their dam for rearing. On day 7 all the animals were killed. Brain weights and visceral organ weights were obtained. There was no significant difference between the MR groups on any measure except stomach weights. ARβMOM pups had larger visceral organ weights than pups in the other groups. ARβMOM and ARβMES pups had similar whole brain weights, smaller than those of the MR pups. However, the cerebellar weights, and to a lesser extent, brainstem weights, showed improvements in the ARβMOM group, over the ARβMES group. Neither the effect of surgery nor of diet alone can account for the organ weight differences that have been described in AR rats. The possibility that normal growth may be primarily dependent on diet at one stage of development, with other factors gaining importance at later stages is discussed.