the analysis of sire buying policies陛下购买政策的分析.pdfVIP

The analysis of sire buying policies J. W. JAMES Station de Génétique Quantitative et Appliquée Centre national de Recherches zootechniques, I.N.R.A., Jouy-en-Josas, France Summary An expression is derived for the net present value of returns obtained through increased productivity of descendants of a purchased sire. This expression is useful for evaluating a given sire purchase, but is not so helpful in determining a sire buying policy. For this purpose, an analysis is made of the value of sire purchase from a breeding nucleus which is making constant genetic gains when the lag of the commercial population behind the nucleus has stabilised under a fixed policy. This leads to a criterion for deciding how long a sire should be used, which depends on price, breeding value, and rate of genetic gain in the nucleus. The optimum sire buying policy depends on the relation between price and breeding value of the sire. Competition for sires may change the relationship of price to breeding value so that no class of sire is the best buy if properly used and it is shown that in this case price is a quadratic function of breeding value. Prices paid by producers for boars auctioned from French performance test stations were found to be related to index value (I) by the approximate equation : = 1 005!- + 50. price (francs) 5(I- 100) (I- 1002). For the observed price function the best policy is to buy boars with high (about o)14 index value, and replace them after r5 months use. The net present value of an average boar is esti- mated as 2 oo0francs. Introduction Most economic assessments of anim