Phenotypic and genetic relationships of feed efficiency with growth performance, ultrasound, and carcass merit traits in Angus and Charolais steers1

Abstract

Feed efficiency is of particular importance to the beef industry, as feed costs represent the single largest variable cost in beef production systems. Selection for more efficient cattle will lead to reduction of feed related costs, but should not have adverse impacts on quality of the carcass. In this study, we evaluated phenotypic and genetic correlations of residual feed intake (RFI), RFI adjusted for end-of-test ultrasound backfat thickness (RFIf), and RFI adjusted for ultrasound backfat thickness and LM area (RFIfr) with growth, ultrasound, and carcass merit traits in an Angus population of 551 steers and in a Charolais population of 417 steers. In the Angus steer population, the phenotypic and genetic correlation of RFI with carcass merit traits including HCW, carcass backfat, carcass LM area, lean meat yield, and carcass marbling were not significant or weak with correlations coefficients ranging from -0.0007 ± 0.05 to 0.18 ± 0.21. In the Charolais steer population, the phenotypic and genetic correlations of RFI with the carcass merit traits were also weak, with correlation coefficients ranging from -0.07 ± 0.06 to 0.19 ± 0.18, except for the genetic correlation with carcass average backfat, which was moderate with a magnitude of 0.42 ± 0.29. Inclusion of ultrasound backfat thickness in the model to predict the expected daily DMI for maintenance explained on average an additional 0.5% variation of DMI in the Angus steers and 2.3% variation of DMI in the Charolais steer population. Inclusion of both the ultrasound backfat and LM area in the model explained only 0.7% additional variance in DMI in the Angus steer population and only 0.6% in the Charolais steer population on top of the RFIf model. We concluded that RFIf adjusted for ultrasound backfat at the end of the test will lead to decreases of both the phenotypic and genetic correlations with carcass backfat and marbling score to a greater extent for late-maturing beef breeds such as Charolais than for early-maturing beef breeds such as Angus. However, further inclusion of ultrasound LM area on top of the final ultrasound backfat in the model of calculating RFI had little effect in reducing the correlations of RFI with the carcass merit traits.

Visceral organ weights, digestion and carcass characteristics of beef bulls differing in residual feed intake offered a high concentrate diet

“…Similarly, McDonagh et al (2001), using steers, Lancaster et al (2009), using bulls, andCruz et al (2010), using steers, Visceral organ and carcass traits in bulls differing in RFI found that RFI had no effect on M. longissimus dorsi area (LMA) in beef cattle consuming a high concentrate diet. Mao et al (2013) also found that RFI had weak or close to zero phenotypic correlations with LMA in Angus and Charolais steers however, genetic correlations between RFI and LMA in both breeds were positive and weak to moderate. The absence of an effect of RFI on LD depth and area in the current and other studies suggests that size of lean muscle tissue may not be the sole contributor to variation in RFI and that biological processes within muscle tissue such as protein turnover and tissue metabolism may have pivotal roles in improved feed efficiency (Herd and Arthur, 2009).…”

“…However Crowley et al (2011), found that the genetic correlation between RFI and carcass fat score was positive (r = 0.33) and Mao et al (2013), found that the genetic correlation between RFI and carcass grade fat was positive (r = 0.42) in Charolais steers but was close to zero (r = 0.02) in Angus steers. Differences in the propensity for fat accreation between different beef breeds, coupled with variation in carcass fat determination, may be contributing to the contrasting genetic correlations between RFI and carcass fatness observed between studies.…”

Accuracy of predicting genomic breeding values for carcass merit traits in Angus and Charolais beef cattle

“…The animal populations, the management of the herds and the descriptive statistics of the five carcass merit traits were reported previously (Mao et al . ).…”

Estimation of genomic breeding values for residual feed intake in a multibreed cattle population1

“…The RFI records for dairy cattle were of 842 Australian Holstein heifers measured at about 6 mo of age (Pryce et al, 2012). The Canadian beef cattle RFI phenotypes consisted of 534 Angus, 384 Charolais (Mao et al, 2013;Chen et al, 2013), and 1,845 mixed synthetic breed (that consisted of the following average breed composi- Abo-Ismail, 2011;Lu et al, 2012). The Holstein heifers and 820 Angus cattle from the New South Wales Department of Primary Industry's Research Centre at Trangie, NSW, Australia, were fed an alfalfa pelleted diet and measured at about 9 mo of age, while the other cattle were fed a finishing feedlot diet and measured at older ages (between 10 and 18 mo of age).…”