This study was conducted to determine the relative contribution of feeding behavior, DMI, apparent DM digestibility (DMD), and passage rate on variation in BW gain. One hundred forty-three crossbred steers were used in this study to determine the factors that contribute to variation in BW gain. Steers were 304 ± 1 d of age and had an initial BW of 338 ± 3 kg. Steers had ad libitum access to feed, and fresh feed was offered twice daily at 0800 and 1500 h. Individual feed intake and BW gains were determined for 106 d. Titanium dioxide was used as an external marker to estimate apparent DMD and passage rate. A multiple-regression analysis was used to determine the relative contribution of initial BW, feed intake, feeding behaviors, digestibility, and passage rate to variance in BW gain, and a path analysis was conducted to determine direct and indirect relationships of the variables. In the regression analysis, initial BW and DMI accounted for 33% of the variation in BW gain. Substituting meal events and meal size for DMI did not increase the amount of variance in BW gain (27%) accounted for by the regression model. There was a slight increase in the variance in BW gain (35%) when apparent DMD was added to initial BW and DMI. When meal events and meal size were substituted for DMI, there was a decrease (30%) in variance accounted for in BW gain. The regression coefficient for the passage rate did not differ from zero (P = 0.63) when the passage rate was substituted for apparent DMD in the regression model that also included initial BW and DMI, nor did it differ from zero (P = 0.39) in the model that substitutes meal events and meal size for DMI. Three models were used in the path analysis. For all 3 models there was a positive correlation (P < 0.001) between DMI and BW gain but not between apparent DMD and BW gain. In all 3 models there was a significant correlation between meal size, meal events, and initial BW on DMI (P < 0.001). Results of both the regression and path analyses suggest that both apparent DMD and passage rate accounted for small proportions of the variance, suggesting that they are minor contributors toward variance in BW gain among cattle fed the same concentrate diet.
Keywords: ADG; DMI; digestibility; feeding behavior; water intake.