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A balance method for the measurement of digestible and metabolizable energy in rats is described. Experimentally determined metabolizable energies of 2 diets for rats were closer to those values for metabolizable energy calculated from tabulated values for pigs rather than chickens. Some drawbacks in the use of tables of energy values to predict the energy of diets are discussed.

In 4-week-old chicks that had been maintained on 3 different diets, caecal weights were lower in germ-free than in conventional birds eating practical but not semipurified diets. There were no consistent differences in total sodium, potassium and chloride ions in the contents of the small intestine. In germ-free chicks the caecal wall muscle appeared lacking in tone and there was a lower concentration of chloride ions in the contents, but there was no caecal enlargement comparable to that in germ-free rodents.