The bovine genome sequence project and the discovery of many thousands of bovine single nucleotide polymorphisms has opened the door for large-scale genotyping studies to identify genes that contribute to economically important traits with relevance to the beef and dairy industries. Large amounts of DNA will be required for these research projects. This study reports the use of the whole-genome amplification (WGA) method to create an unlimited supply of DNA for use in genotyping studies and long-term storage for future gene discovery projects. Two commercial WGA kits (GenomiPhi, Amersham Biosciences, Sydney, Australia, and REPLI-g, Qiagen, Doncaster, Australia) were used to amplify DNA from straws of bull semen, resulting in an average of 7.2 and 67 microg of DNA per reaction, respectively. The comparison of 3.5 kb of sequences from the amplified and unamplified DNA indicated no detectable DNA differences. Similarly, gene marker analysis conducted on genomic DNA and DNA after WGA indicated no difference in marker amplification or clarity and accuracy of scoring for approximately 10,000 single nucleotide polymorphism markers when compared with WGA samples genotyped in duplicate. These results illustrate that WGA is a suitable method for the amplification and recovery of DNA from bull semen samples for routine genomic investigations.

First lactation records of 808,796 artificially sired cows in the Northeast United States were used to compare sire evaluations with and without maternal grandsires in the model. Maternal grandsires were identified on 55.7% of the records. Including maternal grandsire increased percent filled subclasses in absorbed best linear unbiased prediction equations by 43% (Guernseys) to 95% (Holsteins). Rank correlations between sire evaluations for the two models ranged from .91 (Ayrshires) to .97 (Holsteins). Product moment correlations ranged from .92 to .98. Holstein sires changed an average of 52kg of milk. Negative assortative mating (good sires and poor maternal grandsires) was observed in the Guernsey and Brown Swiss breeds. Positive assortative mating (good sires and good maternal grandsires) occurred in the Ayrshires, Holsteins, and Jerseys. Including maternal grandsires of cows in the model is a step toward utilizing more genetic relationships in a practical sire evaluation system.

A Zurich la Commission de Génétique de la F.E.Z. a étalé ses travaux sur cinq séances d'une demi-journée.La première d'entre elle était une séance commune avec la Commission de Production Bovine, sur « les Méthodes d'appréciation de la valeur héréditaire des taureaux laitiers » (modérateur H. O. G RAVERT , R.F.A.).La seconde séance, en commun avec la Commission de Production Porcine traitait de « l'Efficacité économique des programmes de sélection porcine et L.O LLI VI ER , France, en était le modérateur.La troisième séance était organisée avec la Commission de Production Ovine et Caprine, sous la houlette, si l'on peut dire, de V. J AKUBEC (Tchécoslovaquie) et son sujet était « la Productivité des croisements en se basant sur les races ovines prolifiques, en tenant particulièrement compte de la Landrace Finlandaise.Innovation notable, il y avait une séance consacrée à « l'Enseignement de l'élevage des animaux et de la génétique animale », sous la présidence de F. WEBER (Suisse).Enfin la cinquième et dernière séance était une présentation de communi- cations libres qui s'est terminée par une boîte aux suggestions.Comme les années précédentes les A.G.S.A. publient un résumé de toutes les interventions inscrites au programme : rapport principaux, communications et communication libres, dans la langue des intervenants (anglais, français ou alle- mand).

SUMMARYThe selection objective in choosing dual-purpose bulls for use in artificial insemination should be the economic benefit conferred on the population with each insemination. The value of a unit of genetic superiority in the bull for a beef or a dairy trait, as realized through one insemination, depends on two factors—the economic value per unit of superiority and the number of times that superiority is expressed. The economic values are easily established. A standard unit of expression for a trait is defined to be one progeny expression in the year in which the insemination is carried out. A method is developed for summarizing the total genetic consequences of an insemination in these standard units. It takes account of the timing of the insemination, the number of years over which the evaluation is carried out, a discount factor, the dilution of the bull's genotype in his descendants, the female replacement rate, the calf survival rate, and the probability that a surviving calf becomes a dairy cow. The method is independent of the full testing procedures, the intensity of selection, and the level of bull usage. It applies, equally, to selection of bulls for general use and for use in planned matings to produce young sires for testing.

The discounted gene-flow method is used to calculate the effects of varying cow replacement and beef crossing rates on the breeding policy appropriate for a dual-purpose cattle population.It is shown that increasing beef crossing and increasing cow replacement rates both increase the number of expressions of a bull's dairy genotype following one insemination while the expressions of his beef genotype are little affected.The result of this is that (i) a high level of beef crossing is efficient, ( 2 ) more emphasis should be given to dairy traits in selecting bulls, ( 3 ) the return for investment in dairy bull testing and selection is enhanced.