# 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
1. 1I: Initial body weight (kg)
2. 2C: Amount of concentrate offered (% of liveweight)
3. 3OM: Organic matter
4. 4GE: Gross energy
5. 5CP: Crude protein
6. 6EE: Ether extract
7. 7NDF: Neutral detergent fibre