Performance, carcass characteristics and ultrasonic estimates of changes in muscle and fat of bulls, steers and heifers

Among the major problems of beef producers for many years have been those of increasing growth rate, feed efficiency and carcass characteristics of beef animals. Much research has been directed toward the improvement of these traits. The need for more efficient beef production is impelled by the increasing costs of production and competition from other meats. The use of diethylstilbestrol (DES) has resulted in a considerable improvement in growth rate and feed efficiency. The fattening of bulls for the advantage of the naturally produced androgen is a similar practice. The main deterrent to the marketing of bulls has been the lack of consumer and packer acceptance due to the assumption that bull meat is less desirable than steer or heifer meat.

Various attempts have been made to estimate carcass merit of live animals, but thus far no highly accurate method has been developed. Ultrasonic estimates have shown the most promise. An accurate_estimate of a muscle, such as the biceps femoris, with high predictive value for carcass muscling would be an invaluable advance in live animal evaluation. These estimates could provide the basis for more rapid genetic improvement in beef animals.

The objectives of the research reported herein were;

1. To determine the effect of sex on the growth rate, feed efficiency and carcass characteristics of beef animals.

2. To evaluate meat quality among sexes using as criteria mechanical shear scores for tenderness and taste panel scores for tenderness, juiciness and flavor.

3. To develop a reliable method of estimating the carcass muscle of live animals by means of ultrasonics.