Estimation of carcass composition from the cross-section at ribloin of Japanese black steers by computer image analysis

This study was done to make the equations for estimating the carcass composition using the measurements by computer image analysis (CIA) from the cross-section at ribloin of Japanese Black steers. The 24 carcasses were cut between the 6th and 7th rib bone. The total areas, muscle areas, fat areas, ratios of muscle and fat, and the shapes of M.longissimus and M.trapezins were measured from the area encircled between the line from the thoracic vertebra and the vertical line to the thoracic vertebra, and the area encircled between the line from the thoracic vertebra and the line that links the end of the thoracic vertebra and M.ilocostalis by CIA. The actual weights and ratio of muscle and fat were obtained through physical dissection from the left side of the carcass. The muscle weight was estimated for the equation from the rib eye area, muscle % to total area and carcass weight (square R = 94.8%). And then the equation from the rib eye area, fat % to the total area and the carcass weight also highly related to muscle weight (square R = 94.7%). The muscle % of the carcass weight, the fat weight and the fat % of the carcass weight was estimated with the equation from the rib eye area, fat % to total area and the carcass weight (square R = 93.9%, 98.2% and 93.1% respectively). The estimated values from the area encircled between the line from the thoracic vertebra and the vertical line to the thoracic vertebra were higher than those from the area encircled between the line from the thoracic vertebra and the line that links the end of the thoracic vertebra and M.ilocostalis. The rib eye area, fat % to total area at the limited area on the carcass cross-section and carcass weight were important items to estimate the carcass composition.