Phenotypic and genetic relationships of residual feed intake with performance and ultrasound carcass traits in Brangus heifers1

Abstract

The objective of this study was to characterize residual feed intake (RFI) and to estimate phenotypic and genetic correlations with performance and ultrasound carcass traits in growing heifers. Four postweaning feed efficiency trials were conducted using 468 Brangus heifers. The complete Brangus pedigree file from Camp Cooley Ranch (Franklin, TX), which included 31,215 animals, was used to generate genetic parameter estimates. The heifer progeny from 223 dams were sired by 36 bulls, whereas the complete pedigree file contained 1,710 sires and 8,191 dams. Heifers were individually fed a roughage-based diet (ME = 1.98 Mcal/kg of DM) using Calan gate feeders for 70 d. Heifer BW was recorded weekly and ultrasound measures of 12th- to 13th-rib fat thickness (BF) and LM area (LMA) obtained at d 0 and 70. Residual feed intake (RFIp) was computed as actual minus predicted DMI, with predicted DMI determined by linear regression of DMI on mid-test BW(0.75) (MBW) and ADG with trial, trial x MBW, and trial x ADG as random effects. Overall means for ADG, DMI, and RFI were 1.01 (SD = 0.15), 9.51 (SD = 1.02), and 0.00 (SD = 0.71) kg/d, respectively. Stepwise regression analysis revealed that inclusion of gain in BF and final LMA into the base model increased the R(2) (0.578 vs. 0.534) and accounted for 9% of the variation in DMI not explained by MBW and ADG (RFIp). Residual feed intake and carcass-adjusted RFI (RFIc) were strongly correlated phenotypically and genetically with DMI and FCR, but not with ADG or MBW. Gain in BF was phenotypically correlated (P < 0.05) with RFIp (0.22), but not with FCR or RFIc; however, final BF was genetically correlated (P < 0.05) with RFIp (0.36) and RFIc (0.39). Gain in LMA was weakly phenotypically correlated with FCR, but not with RFIp or RFIc; however, gain in LMA was strongly genetically correlated with RFIp (0.55) and RFIc (0.77). The Spearman rank correlation between RFIp and RFIc was high (0.96). These results suggest that adjusting RFI for ultrasound carcass composition traits will facilitate selection phenotypically independent of growth, body size, and carcass composition; however, genetic relationships may still exist between RFI and carcass composition.

Grazed grass herbage intake and performance of beef heifers with predetermined phenotypic residual feed intake classification

“…The base RFI regression model (DMI explained by MLW and ADG) in this study accounted for 0.66 of the variation in DMI, which is comparable to other studies (Lancaster et al, 2008 and2009a;Shaffer et al, 2011) where high forage diets were fed (R 2 range from 0.53 to 0.64). These values are lower than those (0.71 to 0.77) obtained when RFI is determined on cattle fed high-energy diets (Basarab et al, 2003;Lancaster et al, 2009b;Kelly et al, 2010a).…”

Relationship between residual feed intake and enteric methane emission in Nellore cattle

“…A lower coefficient of determination (R 2 = 0.54) was obtained for the estimation of RFI met when the same diet was offered, explaining 54% of the variation in DMI. This value was higher than the 43% observed by Lancaster et al (2009) for heifers fed alfalfabased diet and concentrate, and the 38% observed by Freetly and Brown-Brandl (2013) for heifers fed a high-roughage diet. The short duration (32 d) of ADG measurement may have compromised the calculation of RFI met .…”

Consumo alimentar residual e sua relação com medidas de desempenho e eficiência e características in vivo da carcaça de cordeiros

“…O coeficiente de correlação entre CAR e CA foi significativo (r = 0,63, P<0,01) e maior que os descritos por Arthur et al (2001a), Lancaster et al (2009) e Kelly et al (2010 para bovinos em crescimento de 0,53, 0,59 e 0,46, respectivamente, porém inferior ao estimado para cordeiros (r CAR = 0,73) por Knott et al (2010). Seria importante verificar a existência de correlação genética de mesmo sentido entre tais parâmetros para ovinos, assim como encontrado em bovinos (Lancaster et al, 2009), pois, dessa forma, uma seleção para CAR melhoraria também a conversão alimentar dos animais.…”

“…Seria importante verificar a existência de correlação genética de mesmo sentido entre tais parâmetros para ovinos, assim como encontrado em bovinos (Lancaster et al, 2009), pois, dessa forma, uma seleção para CAR melhoraria também a conversão alimentar dos animais. Apesar da correlação moderada entre CAR e CA no presente estudo, não houve diferença entre as classes de eficiência para este último componente.…”