The performance of a visual image analysis (VIA) system was tested with regards to its potential to determine in vivo carcass composition and conformation, either alone, or in conjunction with other in vivo measures such as live weight and backfat depth. Pigs of both sexes of a commercial type were reared and slaughtered at weights ranging from 50 to 120 kg. Feeding was ad libitum on diets ranging from 0.14 to 0.19 kgkg −1 crude protein content to produce animals of a range of body condition. Two analyses were carried out: the first analysis addressed the relationship between dimensionless carcass and VIA indices; the second analysis assessed the relationship between carcass composition and VIA body shape using detrended carcass and VIA data, which were produced by removal of allometric growth trends.A statistically significant relationship (P<0.05) between in vivo VIA body size and shape and carcass muscle dimensions and composition was found for most body regions. Adjusted R 2 statistics ranged between 0.13 and 0.54 for relative fat weights and between 0.14 and 0.51 for relative lean weights. The predictive power of the regression models, indicated by R 2 -like statistics for prediction, was approximately 70% of the adjusted R 2 values. The descriptive and predictive powers of the corresponding models generally strengthened if VIA indices were combined with other in vivo measurements. The relationships between in vivo and carcass measures remained statistically significant (P<0.05) after removal of the growth trends, although adjusted R 2 statistics generally decreased. The predictive power of models corresponding to the detrended measures was, however, weak.The results show in vivo VIA measurements to be useful in the estimation of muscle size, carcass conformation and composition, all of which are of significant importance to the pig production, marketing and processing industries.
