Residual feed intake in beef cattle and its association with carcass traits, ruminal solid-fraction bacteria, and epithelium gene expression

Table 2 Growth and carcass traits of the most- (n = 6) and the least- (n = 6) efficient beef cattle on RFI testing for 70 d during the finishing period

Items	RFI¹		SE²	Sex		SE³	P-value
Items	Most-efficient animals	Least-efficient animals	SE²	Steers	Heifers	SE³	RFI	Sex	RFI × sex
Growth performance
Initial BW, kg	814.25	836.06	45.95	847.31	803.00	53.05	0.75	0.52	0.87
Final BW, kg	1124.25	1173.63	64.77	1189.88	1108.00	74.79	0.61	0.40	0.59
MMW⁴, kg^0.75	173.06	166.39	5.93	179.50	159.95	6.85	0.45	0.05	0.43
ADG, kg/d	1.83	1.77	0.13	2.02^a	1.57^b	0.15	0.75	0.04	0.91
DMI, kg/d	18.36^b	23.39^a	1.13	22.62	19.13	1.24	0.01	0.06	0.77
RFI coefficient, kg/d	-2.69^b	3.08^a	0.58	0.35	0.043	0.63	< 0.01	0.71	0.52
Carcass traits
HCW⁵, kg	357.56^a	323.53^b	9.61	367.26^a	313.83^b	10.52	0.04	< 0.01	0.66
KPH⁶, %	2.69^a	2.25^b	0.14	2.06^b	2.88^a	0.14	0.05	< 0.01	0.33
REA⁷, cm²	89.40^a	78.52^b	3.20	85.17	82.74	3.51	0.04	0.58	0.62
BFT⁸, mm	12.19	11.81	1.58	11.81	12.19	1.82	0.87	0.87	0.48
Marbling score⁹	457.5	442.5	20.63	407.5^b	492.5^a	23.82	0.62	0.02	0.21
YG¹⁰	2.45	2.97	0.34	2.87	2.56	0.39	0.32	0.54	0.73

Means with different superscripts (^{a, b}) within row represent differences among overall RFI or sex effects (P ≤ 0.05)
¹RFI residual feed intake
²SE standard error of the mean for RFI effect
³SE standard error of the mean for sex effect
⁴MMW midpoint metabolic weight
⁵HCW hot carcass weight
⁶KPH kidney, pelvic, and heart
⁷REA ribeye area
⁸BFT backfat thickness
⁹For marbling score 100 = practically devoid, 200 = traces, 300 = slight, 400 = small, 500 = modest, 600 = moderate, 700 = slightly abundant, 800 = moderately abundant
¹⁰YG yield grade = 2.5 + 0.984 × BFT (cm) + 0.20 × KPH (%) + 0.0084 × HCW (kg) − 0.0497 × LM area (cm²) [67]

ISSN: 2049-1891