| dc.description.abstract | Intensification of cow-calf production by limit-feeding high-energy diets could increase beef production per acre and returns to cow-calf enterprises while reversing the decline in beef cow numbers. To determine the impact of level of intake and dietary energy concentration on digestion, 16 steers (kg BW) fitted with ruminal cannulae were used in a 2×2 factorial experiment. The first factor consisted of ration energy density: high-energy (H; 2.45 Mcal ME/kg) and low-energy (L; 1.94 Mcal ME/kg). The second factor was level of intake 80% (80) or 120% of predicted NRC requirements (120). Intake was assigned individually based on mean treatment intake (g/kg BW.75) of gestating cows from a previous completed project. The experiment consisted of 14-d for adaptation to treatments, 4-d for measurement of intake and digestion, 1-d for determination of ruminal fermentation, and 1-d to determine ruminal fill. There was an energy density by intake level interaction (P = 0.05) for OM intake resulting from a smaller increase in intake for L steers moving from 80 to 120, than the H steers. Organic matter intake was 11.96 and 14.93 g/kg BW for L 80 and L 120, respectively. Steers fed H had OM intakes of 9.06 and 13.71 g/kg BW for 80 and 120, respectively. An energy density by level interaction was observed for digestibility of OM (P < 0.01) and GE (P = 0.02). These interactions result from consistent digestion of L across the two intakes (59 and 61% for 80 and 120, respectively) and a sizeable reduction in H as intake increased (69 and 61% for 80 and 120, respectively). Intake of DE was different between intake level (P < 0.01) and energy density (P < 0.01) with steers offered L consuming 0.138 and 0.178 Mcal/kg BW.75 in 80 and 120, respectively. Steers fed H consumed 0.120 and 0.161 Mcal/kg BW.75 for 80 and 120, respectively. Ruminal fill was greater (P < 0.01) in steers fed L vs. H diets (4.75) versus 3.90 kg DM and for steers consuming 80 versus 120 (P < 0.01, 3.98 versus 4.67 kg DM, respectively). Solid rate of passage was greater (P < 0.01) in steers offered L (2.65) than H (2.20 %/h) and was not significantly different between levels of intake (P = 0.11). Steers responded to dietary energy density and level of intake as expected with the exception of digestion being greater with the low-energy diet than anticipated. | en |
