The R-squared value of M2 (0.79) was higher than that of M1 (0.75) and as a result, body weight at the start of the trial explained a larger proportion of the variation in feed intake than metabolic mid-weight.
Similar to RFI, residual body weight gain (RG) is defined as the difference between actual and predicted body weight gain based on the regression of body weight gain on metabolic mid-weight (MMW) and feed intake [ 9].
Adding any of the linearly regressed traits to a multiple trait selection index may prove useful but similar results may be achieved by applying the appropriate weights to their component traits (feed intake, body weight gain, metabolic mid-weight) [ 6].
Feed intake (FI), metabolic mid-weight (MMW), body weight gain (WG), feed conversion ratio (FCR), residual feed intake (RFI), residual body weight gain (RG), residual intake and body weight gain (RIG, RIG2 and RIG3); due to confounding factors from linear combinations of RFI and RG into RIG traits, correlations were not calculated in some instances.
To identify large-effect QTL, we performed a series of genome-wide association studies and functional analyses using 50 K and 770 K SNP genotypes scored in 5,133 animals from 4 independent beef cattle populations (Cycle VII, Angus, Hereford and Simmental × Angus) with phenotypes for average daily gain, dry matter intake, metabolic mid-test body weight and residual feed intake.
A total of 5, 6, 11 and 10 significant QTL (defined as 1-Mb genome windows with Bonferroni-corrected P-value <0.05) were identified for average daily gain, dry matter intake, metabolic mid-test body weight and residual feed intake, respectively.
Average daily gain (ADG) was calculated as: A D G = weight at end of trial (kg) - weight at start of trial (kg) days on trial and metabolic mid-weight (MMW) was calculated as: M M W = weight at end of trial (kg) + weight at start of trial (kg) 2 0. 75.
Feed intake (FI), metabolic mid-weight (MMW), 16-week body weight (BW16), 20-week body weight (BW20), body weight gain (WG), feed conversion ratio (FCR), residual body weight gain (RG), residual feed intake (RFI), residual intake and body weight gain (RIG, RIG2 and RIG3).
Model 1: FI = μ + b 1 MMW + b 2 WG + hatch + e Model 2: WG = μ + b3 MMW + b4 FI + hatch + e In Models 1 and 2, FI is feed intake over the test period, MMW is the metabolic mid-weight, WG is body weight gain over the test period, μ is the intercept, b 1, b 2, b 3, and b 4 are partial regression coefficients, and e is the residual.
Our findings are consistent with the hypothesis that the residual metabolic burden mid-treatment may correlate with tumour radiosensitivity.
Additionally, the adjusted model of individual metabolic factors (BMI, mid blood pressure, glucose, cholesterol and triglycerides) included all metabolic factors at the same time.
