Table 6.

Quadratic regression equations of dietary CP level (g/kg DM).

	Equation						Maximum 1	p-Value 2
Intake
DM, kg/day	=	−55.380	+	0.876 CP	−	0.00249CP 2	176	0.013
OM, kg/day	=	−50.385	+	0.800CP	−	0.00228CP 2	175	0.013
CP, kg/day	=	−12.008	+	0.160CP	−	0.00040CP 2	200	0.015
NDF, kg/day	=	−18.823	+	0.318CP	−	0.00092CP 2	173	0.015
ADF, kg/day	=	−8.400	+	0.149CP	−	0.00043CP 2	173	0.021
Milk yield
Milk, kg/day	=	−116.980	+	1.652CP	−	0.00470CP 2	176	0.044
4% FCM, kg/day	=	−133.510	+	1.860CP	−	0.00526CP 2	177	0.079
Milk components
Urea-N, mg/kg	=	−940.340	+	11.152	−	0.02711CP 2	206	0.003
Milk components yield
Casein yield, kg/day	=	−4.358	+	0.058CP	−	0.00016CP 2	182	0.070
Urea-N yield, g/day	=	−50.378	+	0.596CP	−	0.00159CP 2	187	0.007
N excretion
Urine output, kg/day	=	−97.997	+	1.315CP	−	0.00352CP 2	187	0.054
Fecal N, g/day	=	−1290.370	+	17.312CP	−	0.04927CP 2	176	0.023
Milk N, g/day	=	−475.590	+	6.927CP	−	0.01893CP 2	183	0.048

¹ Determined by taking the first derivative of the quadratic equation; ² probability value of the quadratic effect of dietary CP level.