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Table 8 True energy efficiency and heat production associated with milk production of sows fed Control (CON; 187.4 g/kg crude protein), Optimal (OPT; 137.8 g/kg crude protein) or Optimal + Leucine (OPTLEU; 142.5 g/kg) diets in early (day 4 to day 8), peak (day 14 to day 18) and overall (day 1 to day 21) lactation period1

From: Reduced protein diet with near ideal amino acid profile improves energy efficiency and mitigate heat production associated with lactation in sows

Early lactation (day 4 to 8)
 Number of sows3121111    
MEmilk, MJ/d446.8944.6540.353.560.8640.3060.595
Milk energy output from diet, MJ/d537.4035.9141.064.540.9700.8350.705
 Milk energy output41.3545.3844.743.710.7180.7910.992
 Milk energy output from body0.468.
True energy efficiency, %679.978.894.07.00.9930.3330.293
 Milk energy from diet789.877.
 Milk energy from body10.
Heat production associated with lactation8, kJ/(d·BW0.75)16013230640.9440.3190.504
Peak lactation (day 14 to 18)
 Number of sows3111111    
MEmilk, MJ/d474.13*72.51*65.06*3.560.9280.1140.222
Milk energy output from diet, MJ/d547.98*61.44*52.34*4.540.1120.7800.347
 Milk energy output51.76*70.21*58.09*3.730.0050.4610.072
 Milk energy output from body0.478.25*
True energy efficiency, %665.
 Milk energy from diet790.686.8*
 Milk energy from body9.413.2*
Heat production associated with lactation, kJ/(d·BW0.75)8414*165211*640.0280.0820.870
Over a 21-day lactation
 Number of sows31199    
MEmilk, MJ/d460.7959.1552.253.680.9240.2290.349
Milk energy output from diet, MJ/d543.1148.4344.385.500.7360.9820.843
 Milk energy output46.9359.3449.564.910.1530.8730.272
 Milk energy output from body−0.629.401.673.820.2410.9000.410
True energy efficiency, %670.582.
 Milk energy from diet791.681.688.35.30.4250.8980.668
 Milk energy from body8.518.411.75.30.4250.8980.668
Heat production associated with lactation, kJ/(d·BW0.75)8289154134600.3210.2480.970
  1. 1Data are least squares means
  2. 2Maximum value of the standard error of the means
  3. 3Sows with an actual feed intake as percentage of predicted > 75% during days 4–8 and days 14–18; for over 21-day lactation, sows have energy balance for both early and peak lactation were used
  4. 4Metabolizable energy (ME) : MEmilk(MJ/d) = MEintake(MJ/d) − MEmaintenance(MJ/d)
  5. 5Milk energy output from diet(MJ/d) = Milk energy output(MJ/d) − Milk energy output from body(MJ/d)
  6. 6\( \mathrm{True}\ \mathrm{energy}\ \mathrm{efficiency}\left(\%\right)=\frac{\mathrm{Milk}\ \mathrm{energy}\ \mathrm{output}\ \mathrm{from}\ \mathrm{diet}\left(\mathrm{MJ}/\mathrm{d}\right)}{{\mathrm{ME}}_{\mathrm{milk}}\left(\mathrm{MJ}/\mathrm{d}\right)}\times 100\% \)
  7. 7\( \mathrm{Milk}\ \mathrm{energy}\ \mathrm{from}\ \mathrm{diet}\left(\%\right)=\frac{\mathrm{Milk}\ \mathrm{energy}\ \mathrm{output}\ \mathrm{from}\ \mathrm{diet}\left(\mathrm{MJ}/\mathrm{d}\right)}{\mathrm{Milk}\ \mathrm{energy}\left(\mathrm{MJ}/\mathrm{d}\right)} \)
  8. 8\( \mathrm{Heat}\kern0.34em \mathrm{production}\kern0.34em \mathrm{associated}\kern0.34em \mathrm{with}\kern0.34em \mathrm{lactation}\left[\mathrm{MJ}/\left(\mathrm{d}\bullet {\mathrm{BW}}^{0.75}\right)\right]=\frac{{\mathrm{ME}}_{\mathrm{milk}}\left(\mathrm{MJ}/\mathrm{d}\right)-\mathrm{milk}\ \mathrm{energy}\ \mathrm{output}\ \mathrm{from}\ \mathrm{diet}\left(\mathrm{MJ}/\mathrm{d}\right)}{{\mathrm{BW}}^{0.75}} \)
  9. *Main effect of period (early and late) was significant (P < 0.05).
  10. Main effect of period (early and late) tended to be significant for true energy efficiency (CON P = 0.086; OPTLEU P = 0.100).