|Globalization of breeding programmes—Opportunities and threats||| Print ||
The dramatically increased trade in frozen semen and embryos, mainly of cattle, and eggs and live animals of other species has led to globalization of breeding programmes of a number of species and breeds. In dairy cattle breeding, for example, bulls of six major breeds, namely Brown Swiss, Guernsey, Holstein, Jersey, Red Dairy Cattle (Ayrshire) and Simmental (dual purpose), are nowadays genetically evaluated on an international basis through the INTERBULL system. Data from about 30 countries from 4 continents are included. South Africa and Australia represent the tropical parts of the world, while represents specialized grazing conditions. By utilizing data on daughters of the same bulls spread in many countries and environments, it has been possible to estimate the genetic correlations between results obtained in different countries. Therefore, genotype by environment interactions that exist between different regions and production systems are considered when estimating the breeding values of individual bulls. These international genetic evaluations have expanded to include mastitis resistance, calving traits, fertility, workability traits and longevity as complements to production and conformation traits. Selection of bulls across countries based on such breeding values has enhanced the opportunities for more correct selection according to the breeding objectives in each region or country. By applying the genotype by environment correlations, more top bulls are also identified globally. This supports the maintenance of a larger genetic diversity compared to the previous situation when all countries used the same top bulls [See www.interbull.org].
The intense global use of a few individual sires introduces a high risk that some of these sires may transmit undesirable genes that are not easily detected when used on a limited scale, e.g., BLAD and CVM. In both cases carrier bulls had been widely used around the world before the defects were discovered. Luckily DNA-tests had been developed for both defects to detect any carrier and are providing a means to omit such bulls from breeding (see Module 4 Section 6). These are just examples of what can happen and probably is happening with yet unknown defects. However, these examples point at the opportunities to find and eliminate recessives that otherwise would have stayed in the population and continued to cause sporadic damage. It underlines the necessity for strict reporting mechanisms to detect any animal with congenital defects. For information on inherited diseases and defects, see [OMIA] or the website (http://omia.angis.org.au/).
Although globalized breeding programmes primarily seem to involve the developed world, they also have an effect on breeding in tropical countries. Usually, the same type of germplasm is marketed in tropical regions as in temperate areas without much analyses of what is needed for each specific market. There are all kinds of reasons to be more critical in developing countries when choosing germplasm from temperate breeds than is currently the case. Increased interest and participation in INTERBULL for information on international comparisons has been recommended for Africa, Asia and Latin America, where the import of semen from exotic breeds from more temperate environments is prevailing or desired ( Philipsson et al., 2005; Interbull Bulletin 33, 2005). Thorough analyses of the national breeding objectives should provide guidelines and improve the opportunities for choice of breeds and individual animals that fit local conditions. Increased participation also helps to be aware of what is going on globally.
|Last Updated on Thursday, 03 November 2011 07:05|