Table 3
Regression equations to estimate intake, digestibility, faecal N, and liveweight

	Regression equation 1,2	r2	Sig. of regression
Intake
Concentrate intake (kg DM/d)	Y = −2.39 + 0.0117(I) + 2.68(C) - 0.348(C2)	0.97	<0.0001
Guinea grass intake (kg DM/d)	Y = 0.701 + 0.00782(I) - 0.321(C)	0.69	0.0002
Rice straw intake (kg DM/d)	Y = 0.747 + 0.00539(I) - 0.00808(C) - 0.209(C2)	0.93	<0.0001
Substitution rate (kg DM/kg DM)	Y = 1.16 - 0.00589(I) + 0.215(C)	0.85	<0.0001
3OM intake (kg/day)	Y = −0.996 + 0.0227(I) + 2.30(C) - 0.535(C2)	0.95	<0.0001
4GE intake (MJ/d)	Y = −18.9 + 0.438(I) + 43.8(C) - 10.1(C2)	0.94	<0.0001
5CP intake (kg/d)	Y = −0.278 + 0.00307(I) + 0.407(C) - 0.0693(C2)	0.97	<0.0001
6EE intake (kg/d)	Y = −0.114 + 0.000818(I) + 0.144(C) - 0.0221(C2)	0.97	<0.0001
7NDF intake (kg/d)	Y = 1.27 + 0.00886(I) - 0.240(C)	0.48	0.0036
Digestibility period
OM digestibility (%)	Y = 54.4 + 8.00(C)	0.84	<0.0001
Digestible OM intake (kg/d)	Y = −0.149 + 0.0106(I) 0.971(C)	0.88	<0.0001
Gross energy digestibility (%)	Y = 75.0 + 13.6(C) - 4.36(C2)	0.43	0.0086
Digestible energy intake (MJ/d)	Y = −7.39 + 0.311(I) + 38.5(C) - 8.75(C2)	0.89	<0.0001
CP digestibility (%)	Y = 56.9 + 6.09(C)	0.63	<0.0001
EE digestibility (%)	Y = 9.28 + 0.0884(I) + 38.8(C) - 7.62(C2)	0.93	<0.0001
NDF digestibility (%)	Y = 59.8 - 8.06(C)	0.63	<0.0001
Faecal N (kg/d)	Y = −0.00168 + 0.000129(I) + 0.0203(C) - 0.00589(C2)	0.89	<0.0001
Liveweight
Initial liveweight (kg)	n.a.	n.a.	0.9905
Final liveweight (kg)	Y = −13.7 + 1.12(I) + 64.9(C) - 15.6(C2)	0.97	<0.0001
Liveweight gain (kg/d)	Y = −163 + 1.43(I) + 773(C) - 185(C2)	0.90	<0.0001