Fresh pork quality has become important and has received more attention as producers and processors try to meet consumer demand for high quality, nutritious products. Many different traits have been investigated as indicators of consumer acceptance of fresh pork. These include color, firmness, pH, intramuscular fat percentage (marbling), waterholding capacity, tenderness, juiciness, and flavor. Each of these has been shown to be low to moderately heritable (Sonesson et al., 1998; Knapp et al., 1997) and to impact consumer acceptance of fresh pork products. However, measuring these traits in the live animal is difficult.

Intramuscular fat percentage (IMF) is one of the meat quality traits which has the potential to be measured in the live animal and has favorable genetic correlations with many of the remaining meat quality traits. Therefore, the primary objective of my Ph.D. research has been the investigation of intramuscular fat percentage of the loin. This has included measuring IMF in the live animal using real-time ultrasound, estimation of genetic parameters for IMF predicted from real-time ultrasound and its relationship with other meat quality traits, the implementation of IMF estimation into a selection project to increase IMF in a population of Duroc swine, and a comparison of different models to estimate breeding values for IMF.