Keith Long, manager of the Bell Ranch, New Mexico, using the Cornell Univ. model for cow efficiency, presented some interesting data at the recent Beef Improvement Federation (BIF) Conference in Lexington, KY. He compared the annual forage requirements of cows differing in size (frame 3, 1027 lb vs. frame 7, 1320 lb) but equivalent in body condition score (5) and in milk production (18 lb/day at peak lactation). The frame 3 cow would have a predicted annual forage requirement of 5.47 T. of DM and would be predicted to wean a steer calf weighing 511 lb. The frame 7 cow’s predicted annual forage requirement would be 6.89 T. of DM and she would be predicted to wean a 573-lb steer calf. Based on these predictions, a herd of 126 frame 3 cows could be run on the same amount of forage as a herd of 100 frame 7 cows. The 126 frame 3 cows would wean 64,386 lb of calf and the 100 frame 7 cows would wean 57,300 lb of calf. Using mid-May, 2003 Amarillo, TX auction prices, 511-lb steers were worth $98.20/cwt while 573-lb steers were worth $92.00/cwt. The difference in gross income would be $10,500 greater for the frame 3 cow herd. Keith indicated that the herd of smaller cows would likely be better matched to the limited forage environment of the very arid Southwest. He went on to suggest that the abundant forage resources of the middle and eastern U.S. could accommodate the larger cows. Keith concluded by saying that one size does not necessarily fit all and that questions still need to be answered regarding cows efficiency: 1) Is a biologically efficient cow necessarily a more profitable cow, and are efficiency and profitability correlated at all levels, or is it a threshold?; 2) What will selection for cow efficiency do to other traits of economic importance? An example of the latter could be the market acceptability of frame 3 calves which would be projected to reach Choice grade at about 1025 lb and their heifer mates at approximately 825 lb. Based on current carcass weight specifications, frame 3 cattle would appear to be an extreme lower limit. At a dressing percentage of 63%, frame 3 steers would be expected to produce 645-lb carcasses, while frame 3 heifer carcasses would weigh only 520 lb. (Long, K. 2003. 35th Annual Beef Improvement Federation Conference and Research Meeting, May 28-31, Lexington, KY).