Table 4.

Regression of apparent total tract digested Ca (g/d) against dietary Ca intake (g/d) of sows fed diets containing 4 levels of calcium carbonate¹

Item	Calcium carbonate
Regression equation	Y = −2.1230 + 0.3318X
SE of slope	0.0186 (P = 0.003)
SE of intercept	0.2705 (P = 0.016)
Coefficient of determination (r2)	0.994
Endogenous loss of Ca, g/d	2.12
Endogenous loss of Ca2, g/kg DM intake	0.79
True total tract Ca digestibility2, %	33.18

¹The number of observations (n) = 36.

²The SE of the endogenous loss was 0.10; the SE for the true total tract digestibility = 1.86 (the SE of the slope × 100).