There is a mathematical model supporting that when growth rate of the chickens is maximized and not constrained by the food-availability, the optimal relationship between body mass and alimentary tract mass should conform to a two-segmented straightened line with different slopes. In the present work we have studied the model using the mass of the intestines as an indicator of growth of the alimentary tract of the Gallus gallus domesticus L. We have observed the slope change of the two segments around a body weight of 90 g that corresponded to two-week-old animals and, at this age it was supposed that the differentiation of the intestine reach the maximum.