The use of ultrasonic fat measurements of 8mm and 10mm as a marketing guide for feeder heifers

One hundred eighty feeder heifers (150 Herford, 29 Angus, and one crossbred) of Choice, Good, and Medium feeder grades were fed to a final back fat thickness of 8mm or 10mm using ultrasonics as the marketing guide. Heifers were purchased at graded feeder calf sales in East Tennessee. After an adjustment period of three weeks, the heifers were fed corn silage ad libitum, treated at the time of ensiling with 10 pounds each of urea and ground limestone plus six pounds of concentrate per head per day, for 110 days, and then full fed a concentrate ration of eight parts ground shelled corn to one part 41 percent cottonseed meal, to finish the heifers at an ultrasonically estimated back fat thickness of 8mm or 10mm. Heifers that were slaughtered when the ultrasonically estimated fat thickness reached 8mm produced carcasses comparable to those of heifers slaughtered at 10mm fat thickness. No significant (P < .05) differences were found between the two fat levels in carcass grade, yield grade, and percent retail yield. The heifers fed to 5mm subcutaneous fat finished 10 days earlier than the 10mm level heifers, and cost per hundred weight gain overall was in favor of the 5mm level heifers by $0.88. Average return over initial investment and feed cost was in favor of the 5mm heifers by $0.75. Results of this experiment indicate that the use of ultrasonics does not penalize either feedlot performance or carcass characteristics, and that using ultrasonics reduces significantly the time the feeder cattle were in the feedlot. Also, that marketing at 8mm fat thickness is just as profitable as marketing at 10mm and shortened the feedlot period by 10 days.