The porosity of egg shells, and the influence of different levels of dietary calcium upon porosity

Abstract

1. An experiment was performed to consider the porosity of egg shells, and the influence of different levels of dietary calcium upon this factor.2. A method was devised for measuring porosity under standard conditions, and the values so obtained are referred to as porosity coefficients.3. The low calcium diet soon led to the cessation of egg production. The few eggs laid showed a tendency to increasing shell porosity as the end of laying approached. On the average these shells had much higher porosity coefficients than shells produced on a normal calcium diet.4. The high calcium diet had no apparent ill effects on two birds, but the other two laid many abnormal eggs. Porosity coefficients in this group were, on the average, lower than in the normal calcium group, but not significantly so. Egg production was as good as on a normal calcium diet.5. The porosity coefficients were significantly higher in period 2 than in period 1, when birds were fed the normal calcium diet throughout; egg production also fell in the second period.6. Eggs other than the first in a clutch do not differ in porosity, but the first egg has a significantly lower porosity coefficient than the remainder. A possible explanation of this is suggested.