MTT Agrifood Research in Finland has conducted research into the impact of two genes on the protein and fat composition of milk and overall milk yield from dairy cows. Researcher Sirja Viitala screened the genome of the Finnish Ayrshire cow, from which among the several chromosomal areas that influence milk production, chromosome 20 became the most significant as the focus of the study. Viitala indentified two genes as contenders responsible for the actions of this chromosome, in particular the effect polymorphisms in them had on milk production. From the research two important discoveries were made:
· In the gene encoding growth hormone receptor, a polymorphism was found to directly determine the dry matter of milk
· In the gene encoding prolactin receptor, a polymorphism was found the protein content of milk
This revelation is not only important in mapping of the bovine genome, but screening of individuals to identify particular traits. Multiplication technology facilitates this, whereby enough material is extracted from a small sample to analyse several chromosomes. It is this process that is applied to extracting a sample from an embryo in vitro without damaging it to establish its sex and the genes affecting milk production. In this way, researchers can select those embryos carrying the desired genes to be the animals that are raised into the dairy herd via surrogates. Using genetic screening for such purposes makes breeding of the dairy herd much more economical and efficient – it eliminates both the chance of the offspring being male (which is useless), and the time taken for a female to display the quality of her milk production (phenotypic expression). Overall this contributes to a larger volume of high quality milk, without unwanted offspring, poor quality cows and hence wastage of pasture.
References:
Science Daily, 2008, Science News: Genetic Information Advances the Breeding of Dairy Cattle, [WWW Page],http://www.sciencedaily.com/releases/2008/11/081117082244.htm
Finnish Ashyre Today, n.d., [Image], www.ayrshire-finland.com/.../kuvat/kisella.jpg
