Table 3.

Summary of the equations used to estimate energy requirements for lactating beef cows in Table 4

Item	BR-CORTE (2016)	NASEM (2016)
SBW, kg	0.88 × BW1.0175	0.96 × BW
EBW, kg	0.8507 × SBW1.0002	0.891 × SBW
NEm, Mcal/d	0.0978 × EBW0.75	0.077 × SBW0.75 × L
MEm, Mcal/d	0.135 × EBW0.75	NEm/Km
Km	NEm/MEm	NEma/ME
NEp, Mcal/d	[CBW × (0.000000793 × DP3.017)]/1,000	$\left[\text{CBW}\times (0.05855-0.0000996\times \text{PD)}\times {\text{e}}^{(0.0323\times \text{PD}-0.0000275\times {\text{PD}}^2)}\text{)}\right]/1,000$
Kp	0.12	0.13
EMp, Mcal/d	NEp/Kp	NEp/Kp
NEl, Mcal/kg milk	0.75	0.72
NEl, Mcal/d	NEmilk × milk yield	NEmilk × milk yield
Kl	Kl = Km	Kl = Km
MEl, Mcal/kg milk	NEmilk/Kl	NEmilk/Kl
MEl, Mcal/d	ELl/Kl	ELl/Kl
NEt, Mcal/d	NEm + NEp + NEl	NEm + NEp + NEl
MEt, Mcal/d	MEm + MEp + MEl	MEm + MEp + MEl

L = lactating factor (1.2 for Nellore cows); Km = efficiency of use of MEm to NEm; NEma = net energy for maintenance available in the diet, calculated as NEma = 1.37 ×ME – 0.138 × ME² + 0.0105 × ME³, where ME is dietary metabolizable energy; NEp = net energy requirement for pregnancy; CBW = calf birth weight (kg); DP = days pregnant; Kp = efficiency of use of MEp to NEp; MEp = metabolizable energy requirement for pregnancy; NE_l = net energy requirement for lactation; K_l = efficiency of use of ME_l to NE_l; ME_l = metabolizable energy requirement for lactation; NEt = total net energy requirement; MEt = total metabolizable energy requirement.