A growth modelling approach to predicting the correlated responses to selection for feeding and growth traits

Mathematical growth models, such as the Brody Growth Curve, provide a means of incorporating the information contained in a series of liveweight measurements into parameters of biological meaning. Variation that exists in these parameters was used to simulate a population of animals and examine the correlated phenotypic responses to selection in feeding, growth and carcass traits. Results are illustrative only because of the lack of model calibration. The average growth curve and daily feed intake (DFI) of a selected cohort was increased by selection on 600 day weight alone in comparison to the average of the unselected population. Conversely, selection on reduced mature weight only decreased these traits, with no apparent effect on feed conversion efficiency (FCE). Selection on combinations of 600 day weight, mature weight and mature feed intake had intermediate effects, however, efficiency increased when selection was for 600 day weight and against mature feed intake. The DFI and FCE at liveweights of 200, 400 and 600 kg were increased by selection for 600 day weight but were reduced by selection against mature weight.