IMF stands for intramuscular fat percent in the longissimus dorsi muscle (rib eye muscle). IMF determination uses real-time ultrasound technology similar to what is used in the medical field to turn ultrasound images into useful selection information. IMF percentage is highly correlated (about 0.70) to the amount of marbling that an animal has in its rib eye, and, of course, this is one of the important considerations that a USDA federal grader uses in determining final quality grade of an animal when it is harvested. IMF is important, but the degree of its importance greatly depends on what you are doing with the progeny of the bull you are selecting. Just about every producer wants the end product of his operation to be a pleasurable eating experience, but unless the operation is maintaining ownership of the calf crop all the way to harvest, the likelihood of seeing added economic returns is slight. However, if you do retain ownership to harvest, the economic incentive of IMF can be quite substantial. In today’s marketplace, it is not unusual for the Choice-Select discount to be over $10/cwt in the carcass, and premium Choice and Prime carcasses can have added premiums anywhere from $6 to $25/cwt in the carcass. Certainly if you are selling your cattle on value-based grid type markets, the ability to have higher percentages in the premium quality grade areas can make large differences in economic returns. When considering this trait in bull selection, it is best to utilize the calculated EPD for IMF because it takes into account how the animal did in comparison to his herd mates, plus how his parents and grandparents stack up to the competition. Do not try to compare actual or adjusted IMF from herd to herd because there is simply too much influence due to herd, nutrition, and testing environment.

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