Evaluation of advanced industry breeding schemes for Australian beef cattle. I. Method of evaluation and analysis for an example population structure

Abstract

A method is presented for evaluating industry breeding schemes for Australian beef cattle. Multitrait selection is considered. The criteria of evaluation are the annual genetic gains in the breeding objective and its component traits, and the net present value of the return from investment in the scheme. The main methods employed by the PC computer program ZPLAN, developed to facilitate such evaluations, are described and are applied to an example population. A deterministic approach is taken to the prediction of annual genetic gain. Various selection groups are defined in the population, each with particular information sources for index selection, and allowing also for two-stage selection. Gene flow methods are applied to assess the discounted return from investment in one round of selection over a defined investment period. The associated fixed and variable costs are calculated, and used to derive the net present value, or profit, from the selection. An example population with a breeding unit of 10000 cows, supplying bulls to a total population of 200000 cows, is envisaged. Seventy percent of the cows in commercial herds are assumed to be mated by bulls derived from the breeding unit. Genetic and biological/technical parameters required by the program are presented. Criteria considered to be available for use in selection are weights at birth and at 200, 400 and 600 days of age. Results are given for individual selection groups and for the whole population. The annual genetic response in the breeding objective ($1.43) comprised $2.21 gain in growth traits (sale weight direct and maternal), $0.37 gain in reproduction traits (cow survival and weaning rates and bull fertility), $0.06 loss in carcass traits (dressing and saleable meat percentages and fat depth), a $1.00 increase in the cost of maintaining cows and a $0.09 loss for increased calving difficulty. The return, cost and profit per cow in the population from one round of genetic selection using the available growth measures was $8.14, $1.34 and $6.81, respectively.