In her doctoral thesis, Research Scientist Sirja Viitala of MTT Agrifood Research Finland demonstrated the impact of two candidate genes on the protein and fat content of milk and on the overall milk yield from dairy cows. The work also involved devising a method for identifying genetic polymorphisms in a sample extracted from a bovine embryo.
Genetic mapping of cattle aims to identify genetic forms that are linked to quantitative trait loci (QTL) which are important for breeding purposes. Sirja Viitala charted scanned the genome of the Finnish Ayrshire cattle in the first phase of her doctoral thesis. Among the many chromosomal areas found to affect milk production, Viitala focused further on the impacts of chromosome 20.
Viitala pinpointed two genes as candidates for the effects in this chromosome and studied what influence polymorphisms in them had on milk production. A polymorphism in the gene encoding growth hormone receptor was found to have a direct impact on the dry matter content of milk. A polymorphism in the gene encoding prolactin receptor, in turn, was associated with the protein yield of milk. Patent protection has been sought for both discoveries.
The results were statistically verified using a separate data set which represents the current Finnish Ayrshire population.
Good dairy cows detected at embryo level
Besides genetic mapping, the research also developed a method for the genetic screening of bovines. The team developed a multiplication technology that allows researchers to extract enough material from a small sample to study several chromosomal areas. This way it is possible to extract a sample from an embryo without harming it, enabling researchers to determine the gender and several genes affecting milk production. The method allows researchers to select embryos containing the desired genes.
Genetic screening speeds up bovine breeding and makes it more efficient. The role of coincidence and the need to collect phenotypic data is reduced when the animals carrying the desired genes are identified very early, optimally before embryo transfer.
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