1. A method of measuring intramuscular fat in an animal comprising the steps of: providing an ultrasonic device operable for producing an ultrasound image from ultrasound waves, said device including a probe for transmitting and receiving ultrasound waves; applying said probe to a selected surface portion of an animal for producing an ultrasound image of an interior muscle portion of the animal, the muscle portion including intramuscular fat, said ultrasound image including speckle produced by scattering of ultrasound waves by the intramuscular fat; storing image data representative of said ultrasound image in a computer, said image data including data representative of said speckle and representing said ultrasound image as a plurality of pixels having respective grey levels; and in said computer, analyzing said speckle in said image data for producing an output indicative of the intramuscular fat in the muscle portion, said analyzing step including the steps of calculating at least one of the variables included in the group comprising the partial autocorrelation of pixel grey levels with selected other pixel grey levels, the correlation of pixel grey levels in a co-occurrence matrix with the pixel values of selected neighbors in said matrix, and nonspeckle area indicated by a run length matrix of pixel grey levels and producing a marbling score without subjective judgment by an individual as a function of said at least one of the variables.