Genetic and phenotypic relationships of feed intake and different measures of feed efficiency with growth and carcass merit of beef cattle

¹ Igenity Livestock Production Business Unit, Merial Ltd.; Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5, Canada
² Alberta Agriculture, Food and Rural Development, Lacombe Research Centre, 6000 C&E Trail, Lacombe, AB, Canada, T4L 1W1
³ Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5, Canada
⁴ Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5, Canada; Agriculture and Agri-Food Canada Research Centre, Lethbridge, Alberta, T1J 4B1 Canada
⁵ Agriculture and Agri-Food Canada Research Centre, Lethbridge, Alberta, T1J 4B1 Canada

^* To whom correspondence should be addressed. E-mail: stephen.moore{at}ualberta.ca.

	Abstract

Feed intake and feed efficiency are economically important traits of beef cattle. This study determined the relationships of daily DMI, feed-to-gain ratio (F:G), residual feed intake (RFI), and partial efficiency of growth (efficiency of ADG, PEG) with growth and carcass merit of beef cattle. Residual feed intake was calculated from phenotypic regression (RFIp) or genetic regression (RFIg) of ADG and metabolic BW on DMI. An F1 half-sib pedigree file containing 28 sires, 321 dams, and 464 progeny produced from crosses between Alberta Hybrid cows and Angus, Charolais, or Alberta Hybrid bulls was used. Families averaged 20 progeny per sire (range = 3 to 56). Performance, ultrasound, and DMI data was available on all progeny, of which 381 had carcass data. Phenotypic and genetic parameters were obtained using SAS and ASREML, respectively. Differences in RFIp and RFIg, respectively, between the most and least efficient steers were 5.59 kg DM/d and 6.84 kg DM/d. Heritabilities for DMI, F:G, PEG, RFIp, and RFIg were 0.54 ± 0.15, 0.41 ± 0.15, 0.56 ± 0.16, 0.21 ± 0.12, and 0.42 ± 0.15, respectively. The genetic (r = 0.92) and phenotypic (r = 0.97) correlations between RFIp and RFIg indicated that the 2 indices are very similar. Both indices of RFI were favorably correlated phenotypically (P < 0.001) and genetically with DMI, F:G, and PEG. Residual feed intake was tendentiously genetically correlated with ADG (r = 0.46 ± 0.45) and metabolic BW (r = 0.27 ± 0.33), albeit with high SE. Genetically, RFIg was independent of ADG and BW but showed a phenotypic correlation with ADG (r = -0.21; P < 0.05). Daily DMI was correlated genetically (r = 0.28) and phenotypically (r = 0.30) with F:G. Both DMI and F:G were strongly correlated with ADG (r > 0.50), but only DMI had strong genetic (r = 0.87 ± 0.10) and phenotypic (r = 0.65) correlations with metabolic BW. Generally, the phenotypic and genetic correlations of RFI with carcass merit were not different from zero, except genetic correlations of RFI with ultrasound and carcass LM area and carcass lean yield and phenotypic correlations of RFI with backfat thickness (P < 0.01). Daily DMI had moderate to high phenotypic (P < 0.01) and genetic correlations with all the ultrasound and carcass traits. Depending on how RFI technology is applied, adjustment for body composition in addition to growth may be required to minimize the potential for correlated responses to selection in cattle.

Key Words: beef cattle, carcass merit, feed efficiency, genetic parameters, performance