The objective of this work was to verify the usefullness of ultrasound to estimate the carcass backfat thickness (EGSC) at slaughter. Twenty four Brangus and 24 Nelore, intact males, were fed with diets containing 20, 40, 60 or 80% of concentrate. Ribeye area (AOLU) and backfat thickness (EGSU) between 12ª and 13ª ribs and the fat thickness over Biceps femoris muscle (EGPU) were collected with a PieMedical Scanner 200 Vet equipment, with linear array transducer of 178 mm coupled with standoff guide, on intervals of approximately 28 days. After 142 days on fed, animals were slaughtered and the carcass backfat thickness (EGSC) was taken, 24 hours after. The correlations between EGSU and EGSC were 0.19, 0.64, 0.74, 0.78, 0.82, 0.80 and 0.86 when taken at 0, 26, 53, 84, 109, 125 and 142 days on fed. Multiple regression equations between breeds, to estimate EGSC showed R² = 0.10 and Sy,x = 2.04 when taken 142 days before slaughter and R² = 0.78 e Sy,x = 0.10 immediately before slaughter. Ultrasound measurements could be useful to sort group of animals to slaughter at same end point.
ribeye area; beef cattle; feedlot; prediction equations; fat thickness; animal production precision
