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

Item	Diet			SEM2	P-value
	CON	OPT	OPTLEU		OPT vs. CON	OPT LEU vs. CON	OPTLEU vs. OPT
Early lactation (day 4 to 8)
Number of sows3	12	11	11
MEmilk, MJ/d4	46.89	44.65	40.35	3.56	0.864	0.306	0.595
MEintake	72.77	71.29	66.52	3.45	0.944	0.375	0.564
MEmaintenance	25.94	26.76	26.02	0.58	0.442	0.992	0.502
Milk energy output from diet, MJ/d5	37.40	35.91	41.06	4.54	0.970	0.835	0.705
Milk energy output	41.35	45.38	44.74	3.71	0.718	0.791	0.992
Milk energy output from body	0.46	8.3	2.01	3.04	0.992	1.000	0.995
True energy efficiency, %6	79.9	78.8	94.0	7.0	0.993	0.333	0.293
Milk energy from diet7	89.8	77.2	90.6	4.7	0.167	0.992	0.132
Milk energy from body	10.2	22.8	9.4	4.7	0.167	0.992	0.132
Heat production associated with lactation8, kJ/(d·BW0.75)	160	132	30	64	0.944	0.319	0.504
Peak lactation (day 14 to 18)
Number of sows3	11	11	11
MEmilk, MJ/d4	74.13*	72.51*	65.06*	3.56	0.928	0.114	0.222
MEintake	100.30*	98.96*	91.31*	3.45	0.955	0.144	0.238
MEmaintenance	26.26	26.26	26.31	0.58	0.999	0.997	0.996
Milk energy output from diet, MJ/d5	47.98*	61.44*	52.34*	4.54	0.112	0.780	0.347
Milk energy output	51.76*	70.21*	58.09*	3.73	0.005	0.461	0.072
Milk energy output from body	0.47	8.25*	2.00	3.04	0.992	1.000	0.995
True energy efficiency, %6	65.2†	86.1	79.5†	7.0	0.106	0.329	0.786
Milk energy from diet7	90.6	86.8*	90.1	4.7	0.837	0.997	0.869
Milk energy from body	9.4	13.2*	9.9	4.7	0.837	0.997	0.869
Heat production associated with lactation, kJ/(d·BW0.75)8	414*	165	211*	64	0.028	0.082	0.870
Over a 21-day lactation
Number of sows3	11	9	9
MEmilk, MJ/d4	60.79	59.15	52.25	3.68	0.924	0.229	0.349
MEintake	86.81	85.89	78.39	3.62	0.978	0.264	0.335
MEmaintenance	26.07	26.74	25.95	0.64	0.670	0.987	0.617
Milk energy output from diet, MJ/d5	43.11	48.43	44.38	5.50	0.736	0.982	0.843
Milk energy output	46.93	59.34	49.56	4.91	0.153	0.873	0.272
Milk energy output from body	−0.62	9.40	1.67	3.82	0.241	0.900	0.410
True energy efficiency, %6	70.5	82.2	83.2	6.3	0.439	0.390	0.993
Milk energy from diet7	91.6	81.6	88.3	5.3	0.425	0.898	0.668
Milk energy from body	8.5	18.4	11.7	5.3	0.425	0.898	0.668
Heat production associated with lactation, kJ/(d·BW0.75)8	289	154	134	60	0.321	0.248	0.970

¹Data are least squares means

²Maximum value of the standard error of the means

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

⁴Metabolizable energy (ME) : ME_milk(MJ/d) = ME_intake(MJ/d) − ME_maintenance(MJ/d)

⁵Milk energy output from diet(MJ/d) = Milk energy output(MJ/d) − Milk energy output from body(MJ/d)

⁶$\text{True energy efficiency}\left(\%\right)=\frac{\text{Milk energy output from diet}\left(\mathrm{MJ}/\mathrm{d}\right)}{{\mathrm{ME}}_{\text{milk}}\left(\mathrm{MJ}/\mathrm{d}\right)}\times 100\%$

⁷$\text{Milk energy from diet}\left(\%\right)=\frac{\text{Milk energy output from diet}\left(\mathrm{MJ}/\mathrm{d}\right)}{\text{Milk energy}\left(\mathrm{MJ}/\mathrm{d}\right)}$

⁸$\mathrm{H}\mathrm{e}\mathrm{a}\mathrm{t}\mathrm{p}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{a}\mathrm{s}\mathrm{s}\mathrm{o}\mathrm{c}\mathrm{i}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{d}\mathrm{w}\mathrm{i}\mathrm{t}\mathrm{h}\mathrm{l}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}[\mathrm{M}\mathrm{J}/\left(\mathrm{d}\bullet {\mathrm{B}\mathrm{W}}^{0.75}\right)]=\frac{{\mathrm{M}\mathrm{E}}_{\mathrm{m}\mathrm{i}\mathrm{l}\mathrm{k}}\left(\mathrm{M}\mathrm{J}/\mathrm{d}\right)-\mathrm{m}\mathrm{i}\mathrm{l}\mathrm{k}\mathrm{e}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y}\mathrm{o}\mathrm{u}\mathrm{t}\mathrm{p}\mathrm{u}\mathrm{t}\mathrm{f}\mathrm{r}\mathrm{o}\mathrm{m}\mathrm{d}\mathrm{i}\mathrm{e}\mathrm{t}\left(\mathrm{M}\mathrm{J}/\mathrm{d}\right)}{{\mathrm{B}\mathrm{W}}^{0.75}}$

^*Main effect of period (early and late) was significant (P < 0.05).

^†Main effect of period (early and late) tended to be significant for true energy efficiency (CON P = 0.086; OPTLEU P = 0.100).