Milk-borne factors affect survival, intestinal growth and development in newborn rats

Early milk of rats contains high concentrations of many hormones and growth factors. Studies were undertaken to evaluate the physiological effects of early rat milk infranatant, insulin-like growth factors (IGFs) and epidermal growth factor (EGF) upon the growth and development of intestinal tissues in newborn rat pups. In one study, pups were artificially reared for 3 days (d2-d5) then fostered back to the dam. Treatment groups were mother fed controls (MF), artificially reared pups fed rat milk replacer (RMR) or RMR with infranatant from rat milk (r-Infra) or bovine milk (b-Infra). After 8 days, survival in the MF and RMR + r-Infra groups was 100% while survival in the RMR + b-Infra and RMR groups were 50 and 30% respectively. In additional experiments, pups were separated from the dam at birth (no suckling) and sacrificed after 2 days of artificial feeding. Treatments included RMR, RMR + r-Infra, and RMR + long Arg-IGF-I + EGF and were compared to MF control. Histological and autoradiographical evaluation of the intestines from MF controls showed advanced differentiation characterized by proliferative cell populations which were restrictively localized to the basal areas of the mucosa. In contrast, intestinal proliferation in the RMR group was diffusely distributed along both the lower regions of the villi and the crypts. Pups fed RMR + r-Infra exhibited intermediate morphology. Pups artificially fed RMR + long Arg-IGF-I + EGF produced a dramatic establishment of an active crypt-villus axis within two days of feeding.(ABSTRACT TRUNCATED AT 250 WORDS)