The analysis of sire buying policies

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 : price (francs) = 1 500 + 5(I- 100) + 0.5 (I- 100)2. For the observed price function the best policy is to buy boars with high (about 140) index value, and replace them after 15 months use. The net present value of an average boar is estimated as 2 000 francs.L’achat d’un géniteur sélectionné conduit à des gains de productivité dans sa descendance. Une expression de la valeur nette actualisée des recettes qui en résultent est établie. Cette expression est utile pour juger de la valeur d’un achat donné mais elle n’est pas suffisante pour déterminer une politique générale d’achat de géniteurs. Dans ce but, une analyse est faite de la valeur d’un achat de mâle en provenance d’un noyau de sélection qui réalise des gains génétiques constants quand le retard de la population commerciale sur le noyau s’est stabilisé en fonction d’une politique donnée. Cela conduit à un critère pour décider de la durée d’utilisation d’un mâle, qui dépend de son prix, de sa valeur génétique et du progrès génétique dans le noyau. La politique d’achat optimale dépend de la relation entre le prix et la valeur génétique du mâle. La concurrence entre les acheteurs peut modifier la relation entre le prix et la valeur génétique, et aboutir à une relation telle que tous les pères ont la même valeur nette actualisée à condition qu’ils soient convenablement utilisés. Il est montré que, dans ce cas, le prix est une fonction de second degré de la valeur génétique. Les prix payés par les producteurs pour les verrats vendus aux enchères dans les stations françaises de contrôle individuel sont liés à la valeur de l’indice (I) par la relation approchée : prix (francs) = 1 500 + 5(I- 100) + 0.5 (I- 100)2. Pour une telle fonction, la meilleure politique, pour le producteur, consiste à acheter des verrats à haut indice (environ 140) et à les remplacer après une utilisation de 15 mois. La valeur nette actualisée d’un verrat moyen est estimée à 2 000 francs

Selection theory with overlapping generations

International audienc

Detection of cytoplasmic effects on production: the influence of number of years of data

International audienc

Genetic interaction between sire and population of mates in Drosophila melanogaster

International audienc

Optimal allocation of resources considering two sexes and selection in two stages

The distribution of limited testing resources between sexes and stages of selection was optimised for breeding structures employing one- or two-stage selection. The use of incomplete sampling was considered. Measurement expenditure generally favoured the sex subject to the highest selection intensity. Within a sex, the optimal intensity of measurement was dependent upon the proportion of available candidates required for breeding and on the level of available funding. It was optimal to test all of the available candidates when more than 40% was required for breeding. Single-stage selection was favoured when selection intensity was low and when the funding limit was high. The allocation of resources between stages of selection was complex. Results are expressed graphically for different relationships between measurement cost and selection accuracy, for a range of selection intensities in each sex, and for a range of funding limitations. The methods are applicable to any livestock industry where multi-stage selection is utilised and where a relationship between measurement cost and accuracy can be ascertained. A numerical illustration pertinent to a wool sheep breeding scheme is examined

Optimum family size for progeny testing in populations with different strains

International audienc

Efficacy of personalized cognitive counseling in men of color who have sex with men: secondary data analysis from a controlled intervention trial.

In a previous report, we demonstrated the efficacy of a cognitively based counseling intervention compared to standard counseling at reducing episodes of unprotected anal intercourse (UAI) among men who have sex with men (MSM) seeking HIV testing. Given the limited number of efficacious prevention interventions for MSM of color (MOC) available, we analyzed the data stratified into MOC and whites. The sample included 196 white MSM and 109 MOC (23 African Americans, 36 Latinos, 22 Asians, eight Alaskan Natives/Native Americans/Hawaiian/Pacific Islander, and 20 of mixed or other unspecified race). Among MOC in the intervention group, the mean number of episodes of UAI declined from 5.1 to 1.6 at six months and was stable at 12 months (1.8). Among the MOC receiving standard counseling, the mean number of UAI episodes was 4.2 at baseline, 3.9 at six months and 2.1 at 12 months. There was a significant treatment effect overall (relative risk 0.59, 95% confidence interval 0.35-0.998). These results suggest that the intervention is effective in MOC