ONTOGENY OF INTESTINE MORPHOLOGY AND INTESTINAL DISACCHARIDASES IN CHICKENS (GALLUS-GALLUS) FED CONTRASTING PURIFIED DIETS

Two groups of growing posthatching Cornish x Rock cross chickens were fed with either a carbohydrate-containing (52.5%) or a carbohydrate-fr ee diet. At 36 days after hatching some of the chicks in each group we re shifted to the opposite diet. Chickens fed on a carbohydrate-contai ning diet grew faster and achieved higher asymptotic masses than chick ens fed on a carbohydrate-free diet. Chickens fed on a carbohydrate-fr ee diet had longer intestines and larger intestinal areas than chicken s of the same mass fed on a carbohydrate-containing diet. In both grou ps sucrase and maltase activity (standardized by either intestinal are a or mass) increased from day 1 to approximately day 17. After day 17, chickens fed on a carbohydrate-containing diet exhibited 1.8 and 1.9 times higher sucrase and maltase activities per unit intestinal area, respectively, than chickens fed on a carbohydrate-free diet. Analysis of covariance was used to estimate the contribution of sucrase and the sucrase-independent maltases to maltase activity, and to estimate the effect of diet on the sucrase-independent maltases. Sucrase contribut ed 80% and 75% of the maltase activity in carbohydrate and carbohydrat e-free fed chickens, respectively. Chickens shifted from a carbohydrat e-free to a carbohydrate diet converged in gross intestinal morphology and intestinal sucrase and maltase levels with carbohydrate-fed chick ens within 8 days. Chickens shifted from carbohydrate to carbohydrate- free diets, in contrast, did not show appreciable changes in intestina l length and after 8 days had not reduced levels of sucrase and maltas e to those of chickens fed on the carbohydrate-free diet. A comparison of integrated maltase intestinal activity with published data on gluc ose uptake showed that the ratio of maltose hydrolysis to glucose upta ke seemed to be about 7 and to remain relatively invariant during onto geny. Because so little is known about the interaction between hydroly sis and uptake in vivo, it is difficult to determine if this relativel y high ratio represents excess hydrolytic capacity or if it is needed to provide high lumenal glucose concentrations that maximize uptake.