Compositional changes in mature cows using real-time ultrasonic measurements
Hicks, Carole Lynn
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Eighty - four Angus and forty - four Hereford cows were used in this study to evaluate changes in body composition using real - time carcass ultrasound measures. Cows were scanned and weighed at four times during the course of a year: pre-breeding (March), between breeding and weaning (July), weaning (September), and pre-calving (December). Comparisons were made across age, YW EPD, and MILK EPD classes. Ribeye area (REA), back fat (BF), and rump fat (RF) and weight decreased from pre-breeding to weaning then increased to pre-calving. Changes in REA/kg and marbling were variable and few measures were significantly different (P < 0.05). Among the comparisons, old cows, high YW, and low MILK cows were generally heavier, had larger REA, and more fat cover (both BF and RF) than young, low YW, and high MILK cows. The analysis of the compositional changes in Hereford cows was inconclusive. The compositional changes measured by ultrasound were consistent with the expected changes in beef cows during a normal production cycle, suggesting that ultrasound is a viable, objective measure of mature cow composition.