Optimising selection on growth and carcase development trajectories in lamb

Net benefit of response to selection for weight, fat and eye muscle depth measured at different ages was optimized for lamb production systems. Optimised selection response and profit were compared for an index based on random regression coefficients relating to the whole growth trajectory and an index based on breeding value for weight, fat and muscle at 200 days. Three different price structures were considered with various premiums for fat and muscle. No significant additional benefit was gained from using random regression breeding value over selection for traits at 200 days of age for a terminal sire breeding objective. However more additional benefit might be expected for a case where maternal performance is considered in the objective or when feed costs are high.