Estimation of the metabolisable energy requirements of feedlot light lambs and comparison with the U. S. National Research Council predictions

Figures & data

Table 1. Chemical and biological characteristics of the concentrates (dry matter basis).

	Concentrate
	CON	CAM	FIB
Organic matter, %	92.6	91.2	89.8
Crude protein, %	17.6	17.5	17.8
Crude fat, %	4.8	4.6	4.4
In vitro organic matter digestibility, %	83.2	82.9	74.1
Metabolisable energy (ME), MJ/kg	11.7	11.5	10.1
Diet ME^1, MJ/kg	11.5	11.3	9.9
Efficiency of ME use for gain	0.43	0.43	0.38

¹Assuming that the diet was comprised of 95% concentrate and 5% barley straw on a dry matter basis. See the text for details.

Table 2. Least squares means of growth performance, feed intake and metabolisable energy intake (MEI) of Manchega male lambs from the first week of fattening until slaughter and metabolisable energy requirements (MER) predicted by the U. S. National Research Council (NRC).

Measured parameters	Weeks on fattening
	1	2	3	4	5	6	SEM	P
Body weight, kg	14.4^f	16.0^e	18.2^d	20.5^c	22.5^b	24.5^a	0.39	<0.001
Daily weight gain, g/d	136^b	337^a	346^a	304^a	285^a	356^a	10.93	<0.001
Dry matter intake, g/d	530^d	860^c	864^c	985^bc	1020^ab	1129^a	23.8	<0.001
MEI, MJ/d	5.36^d	8.73^c	8.76^c	9.97^b	10.33^b	11.45^a	0.224	<0.001
NRC predictions^1
MER Model 1, MJ/d	5.18^c	8.17^b	9.15^b	9.45^b	9.59^b	11.98^a	0.259	<0.001
MER Model 2, MJ/d	4.75^a	7.50^b	8.39^b	8.67^b	8.80^b	10.99^a	0.238	<0.001

¹Model 1 includes an adjustment of the metabolisable energy required for maintenance for the effect of the level of metabolisable energy intake on visceral organ tissue energy use, while such adjustment is not included in Model 2. Within a row, least squares means without a common superscript are different by Tukey test at p < 0.05. SEM: standard error of the mean.

Table 3. Performance of the U. S. National Research Council method for predicting the metabolisable energy requirements of fattening light lambs.

Statistics	Models^a
	Model 1	Model 2
R^2	0.66	0.66
RMSEP, MJ/d	1.45	1.63
RMSEP, % mean	15.96	17.93
RSR, % standard deviation	32.52	36.55
CCC	0.80	0.74
Central tendency error, % total error	1.57	31.66
Linear error, % total error	22.52	10.62
Random error, % total error	72.91	57.72

^aModel 1 includes an adjustment of the metabolisable energy required for maintenance for the effect of the level of metabolisable energy intake on visceral organ tissue energy use, while such adjustment is not included in Model 2. R²: coefficient of determination. RMSEP: root mean square error of prediction. RSR: standardised RMSEP. CCC: concordance correlation coefficient.

Data availability statement

The data that support the findings of this study are available from the corresponding author, [A. L. M. M.], upon reasonable request.