Four experiments were conducted to evaluate intake and measures of feed efficiency in beef cattle. In Exp. 1 and 2, measures of feed efficiency were calculated on Angus and SimAngus heifers (Exp.1; n = 623, and Exp. 2; 404); and heifers were classified as either high, medium, or low residual feed intake (RFI), residual BW gain (RG), residual intake and BW gain (RIG), and DMI. The objective of these experiments was to determine the relationship between post-weaning feed efficiency and intake in heifers, and subsequent cow performance, reproduction, and longevity as 2-and 5-yr-old cows. As heifer RFI improved, cow forage DMI was reduced in both 2-and 5-yr old cows (P < 0.01) and resulted in more desirable 2-yr old cow efficiency (P < 0.01). Heifer RFI classification did not affect (P ≥ 0.07) reproductive traits, cow production traits, or herd longevity up to 5 yr of age. Heifer RG classification did not affect (P ≥ 0.08) reproductive traits; cow production traits, cow efficiency, or DMI in 2-yr-old cows. As heifer RIG improved, 2-yr-old cow forage DMI was reduced (P < 0.01) during lactation, resulting in more desirable cow efficiency (P=0.02). Heifer RIG classification did not affect (P ≥ 0.12) reproductive traits; calf birth or weaning BW; cow BW, milk production, 12th rib fat thickness, or BCS in 2-yr old cows. Heifer DMI was highly correlated (P < 0.05) to cow forage intake as both 2- and 5-yr-old cows. Heifers classified as low DMI were least frequently (P < 0.01) kept as replacements and were youngest (P = 0.04) at first calving. Calves from 2-yr-old cows, classified as high DMI heifers, had the greatest (P < 0.01) birth BW; yet, there were no differences (P=0.60) in weaning BW. Intake classification had no effect (P ≥ 0.07) on cow BCS, 12th rib fat thickness, or milk production in either 2- or 5-yr-old cows. Cows, classified as low DMI heifers, weighed the least (P = 0.02) and had reduced (P < 0.01) hip heights as both 2- and 5-yr old cows. Cows, classified as low DMI heifers, had reduced (P ≤ 0.01) DMI, improved (P = 0.01) cow efficiency, and a greater percentage of females remaining in the herd at 5 yr of age. These data indicate that females classified as more efficient have reduced cow DMI without compromising production traits and longevity. Heifer DMI is an accurate predictor of cow forage intake at different biological time points in life. In Exp. 3, measures of feed efficiency were determined in Angus and Simmental X Angus heifers (n=263), and heifers were classified within feed intake and efficiency groups as described in Exp. 1 and 2. The objective of this experiment was to determine the relationship between measures of heifer feed efficiency and mature cow intake of forage of divergent quality. At 5 or 6-yr of age, cows were evaluated for voluntary forage intake of high-quality forage (HQDMI) and poor-quality forage (PQDMI). Heifer RFI classification had no effect on cow production traits; yet, cows classified with the least desirable heifer RFI had the greatest (P ≤ 0.05) HQDMI and PQDMI. Heifer RG classification had no effect on cow production traits or DMI. Heifer RIG classification had no effect on cow traits. Cows classified as low RIG heifers had the greatest (P = 0.02) HQDMI; yet, only tended to have the greatest PQDMI (P = 0.09). Cows classified as high DMI heifers were heavier (P = 0.05) and had greater (P < 0.01) DMI than cows classified as low or medium DMI heifers. This study suggests that feed costs can be reduced by selection for heifer RFI, RIG, and DMI. In Exp. 4, Charolais crossbred heifers and steers (n=628) endured two performance and intake tests during the growing and finishing phases of the feedlot phase. Objectives were to determine the effects of test period duration, timing, and diet type on measures of feed efficiency in feedlot calves. Dry matter intake and RFI were repeatable (r=0.56; P<0.01, and 0.63; P<0.01, respectively) for both periods of grain-fed steers. Average daily gain was not repeatable (r=0.11; P=0.06) across both test periods for steers. However, growing and finishing ADG were correlated (r=0.58; P<0.01, and r=0.69; P<0.01, respectively) to total feeding period ADG. Regardless of test length, from 7 to 70d, DMI was correlated (r≥0.87; P<0.01) to total DMI during the growing period. Heifer forage DMI was correlated (r=0.58; P<0.01) to grain DMI. Forage and grain RFI were moderately correlated (r=0.40; P<0.01) for heifers. These data indicate that DMI is repeatable across varying stages of maturity in cattle, and accurate feed efficiency measures can be obtained in either the growing or finishing period. The relationship of forage and grain DMI and efficiency in heifers suggests that measures of DMI and feed efficiency are relevant, regardless of diet fed. Intake evaluation periods can be shortened without losing accuracy in predicting individual animal DMI; and measures of feed efficiency can be calculated by decoupling performance and intake information. Collectively, these experiments provide insight into the effects of DMI and feed efficiency on many production traits; and the potential methods in which both feedlot and cow-calf producers can improve profitability within their operations
