28 
~ N . C. Agricultural Experiment Station 
DISCUSSION 
The feed records show that the appetite kept up fairly well for birds not having 
exercise. This is of interest in view of the fact that it is a check on the hens which 
were used in the digestive coefficient work where with single feeds the birds soon went 
off feed. In these cases the fowls received a variety of feed. 
From these preliminary tests it is seen that a bird may go 365 days without being 
fed grit, and have plenty of grit remaining in its gizzard with which to grind its feed. 
The grit that had remained in the gizzard 365 days appeared just as sharp as that 
found in the gizzard at the commencement of the tests. In fact we do not believe 
that the grinding process in the gizzard of the fowl is one of sharp cutting processes, 
but rather the following process. The food soaks more or less in the crop depending 
on the length of time it remains there. The food passes from the crop through the 
second portion of the esophagus to the proventriculus where it soaks in a strong acid 
secretion. From the proventriculus the food passes into the gizzard where the muscles 
of the walls of the gizzard contract, squeezing the soaked grain among the grit and 
by a squeezing rotary motion the food is reduced to fineness and is more like the action 
of a ball mill. Birds hold their weight and remain perfectly healthy on either sharp 
or dull grit. 
There is a tendency for a fowl to eat more grit than is essential for grinding the food. 
In another series of experiments we have shown that the amount of mineral given 
off for the first twelve days was much more than that taken in. Further experiments 
showed that this was due to the grit passed off from the gizzard. While there is a 
tendency to pass off the excess grit and to keep a residual amount, yet the amount 
retained varies greatly with different individuals. 
One hen at the end of 365 days had 5.89 grams of grit, as much as one of the hens 
that was killed for examination on the thirty-sixth day. One hen that died on the 
one hundred and fifty-sixth day had 14.03 gms., or more than that contained by the 
gizzards of the hens killed on the fourteenth day and twenty-first day. As shown by 
the health of the birds, a fowl may go longer than a year without replenishing her grit. 
