Table VII.- Prediction of the composition of empty body weight gain (g/kg EBWG) of Ca, P, Na, K and Mg at different BW of Dorper x Hu ewe lambs.
By deriving the logarithm regression equations of the body content for Ca, P, K, Na, and Mg according to the logarithm of the EBW, the equations to predict these nutrients per kilogram of EBWG were obtained in Table VII.
The macromineral element deposition of ewes in EBWG (Table VII) followed the same concentration pattern as in EBW (Table VI), with increases of approximately 2.29% for Ca, 1.96% for P, 4.82% for K, 5.44% for Mg and decreases of 3.42% for Na, respectively, as BW increased from 35 to 50 kg.
The net protein requirement for weight gain was calculated as the multiple linear regression of retained protein (RP, g [day.sup.-1]) in EBWG (kg [day.sup.-1]) and of RE (Mcal [day.sup.-1]), by equation:
RP = [[beta].sub01] + [[beta].sub.1] X EBWG + [[beta].sub.2] X RE
The conversion of empty body gain (EBWG) into body weight gain (BWG) was obtained by the following equation: EBWG = 0.880 x BWG and the coefficient found was lower than 0.951 suggested by NRC (2000).
Regression equation which described the relation between the retained energy (RE, Mcal [day.sup.-1]) and daily empty body gain (EBWG) in a specific EBW was: RE = 0.044 X [EBW.sup.0.75] X [EBWG.sup.1.1302] ([R.sup.2] = 0.81).
A multiple regression of the retained protein (RP, kg [day.sup.-1]) as a function of RE (Mcal [day.sup.-1]) and of EBWG (kg [day.sup.-1]) was due to the interaction of protein and fat deposition to estimate net protein requirements (Table 5): RP (g [day.sup.-1]) = - 31.45 + 229.69 x EBWG - 8.75 X RE ([R.sup.2] = 0.96).
By deriving regression equations of the body content logarithm for microminerals as a function of the EBW logarithm, we obtained the prediction equations of these nutrients per kg of empty body weight gain (EBWG) and the amount of nutrients stored in g [kg.sup.-1] EBWE, in the different weight ranges (Table 4).
Micromineral deposition in weight gain (g [kg.sup.-1] EBWG; Table 4) followed the same concentration trend in the empty body (g [kg.sup.-1] EBW; Table 3), showing slight increases of 6.82% for Zn, 1.69% for Fe, 0.15% for Mn and 25.82% for Cu when body weight increased from 15 to 25 kg.
Micromineral contents from EBWG meet the net requirements for a 1-kg EBWG.