On the Associations Between Linear Body Measurements, Feeding Behavior Traits and Feed Efficiency Measures in Finishing Steers

Animal size and feeding behavior patterns may be associated with feed efficiency considering the energy metabolism linkage between these factors. However, these associations may differ partially according to the efficiency measure used. Thus, objectives were to evaluate the associations between linear body measurements, feeding behavior and different measures of efficiency in finishing steers. A group of 61 steers (initial BW=401±54.20 kg) was tested over a 142-d period. Steers were fed a corn-based diet (with two different levels of vitamin A supplementation) allowing for ad libitum consumption. Feed intake was individually measured using the Insentec feeding system. Six productive performance traits were calculated: daily dry matter intake (DMI), daily DMI relative to BW (DMIp), average daily gain (ADG), residual feed intake (RFI), residual gain (RG), and gain to feed ratio (G:F). Body measurements of body length (BL), hip height (HH), hip width (HW), heart girth (HG), mid-girth (MG), and flank girth (FG) were performed on days 1 and 142. Feeding behavior traits consisted of events per day (meals/day; visits/day), eating time (min/visit; min/meal; min/day), and eating rate (g of DM/visit; g of DM/meal; g of DM/day). The associations between body measurements, feeding behavior and efficiency measures were measured through partial correlations, adjusted for dietary treatment, using the MANOVA/PRINTE statement within the GLM procedure of SAS. Among animal size traits, BL, HH, HG, MG and FG were all negatively correlated with G:F (range: -0.25 to -0.55, P≤0.05), while no correlations were found when looking at RG and RFI. The HG was positively associated with ADG (r=0.36, P=0.004) and DMI (r=0.71, P=0.0001), and negatively associated with DMIp (r=-0.23, P=0.05) and G:F (r=-0.55, P=0.0001). Among feeding behavior traits, meals/day (r=0.34), visits/day (r=0.35), g of DM/day (r=0.52) and g of DM/visit (r=0.33) were all correlated with RFI (P≤0.05). Interestingly, the eating time (min/day) was negatively associated with G:F (r=-0.25, P=0.05) and positively associated with RFI (r=0.52, P=0.0001). In general, our results reinforce that G:F ratio is highly dependent on animal linear body measurements (i.e. size), in contrast to the measures of RG and RFI. Additionally, feeding behavior traits and therefore animal activity may be important factors regulating efficiency of feed utilization. Thus, the selection criteria based on efficiency measures should take into account animals’ stage of production and outputs of interest of the overall production system.