Fat deposition in a broiler sire strain. 5. Comparisons of economic efficiency of direct and indirect selection against fatness.

In a simulation study, selection for weight gain in a broiler sire strain was compared with 1) one and two stage index selection for weight gain and feed conversion and 2) weight gain, slaughter yield, and percentage abdominal fat. Weight gain per day was assigned an economic value of 1.138 Dutch cents (ct)1/g; feed conversion, -138.18 ct/1.0; slaughter yield, 0 or 7.55 ct/%; and percentage abdominal fat, 0 or -10 ct/%. When selection was completely or almost completely (as in two stage selection) based on weight gain, percentage abdominal fat increased; otherwise it decreased. Weight gain, feed conversion, and slaughter yield improved with all selection methods examined. Due to the high positive correlation between feed conversion and percentage abdominal fat, selection for an index of weight gain and feed conversion gave about the same reduction in percentage abdominal fat as selection for an index of weight gain, slaughter yield, and percentage abdominal fat. Selection response of the four traits was dependent more on selection methods than on sets of economic values. Based on economic values, selection for an index of weight gain and feed conversion gave 1.70 to 3.35 times the financial gain of selection for weight gain only, and selection for an index of weight gain, slaughter yield, and percentage abdominal fat gave 1.15 to 3.12 times that attained by selection only for weight gain. The extra financial gains exceeded by far the estimated additional costs of the index selection methods.