Brussels, 21 Feb 2003
A gene that regulates the yield as well as the protein and fat content of milk has been discovered by a group of Belgian and Finnish scientists.
MTT Agrifood Research in Finland and the University of Liège, Belgium, have found a variation in the growth hormone receptor gene in the bovine chromosome 20, which scientists claim greatly effects the milk yield and nutrient composition in Ayrshire, Holstein and Jersey cows.
The impetus of the study came from EURIBDIS, a biotech project funded under the Fourth Framework Programme that carried out the sparse mapping of the entire genome of the Finnish Ayrshire. The project involved six European research groups and was completed in 2001.
This is not the first time that a quantified association has been made between a single gene and bovine milk production. However as Johanna Vilkki of MTT Agrifood Research points out, 'Developing associated markers for genes that affect milk traits is not highly prioritised in breeding since it is relatively easy to improve these traits by conventional selection.'
Dr Vilkki is confident, however, that the discovery will facilitate the selection of bulls that father high milk-producing cows.
The scientists involved in the project believe that a cost effective version of the gene will increase the average protein content in milk by 0.06 per cent and the fat content by 0.15 per cent. However, they warn that the increase in fat and protein content might be at the expense of total milk yield.
Dr Vilkki suggested that an increased milk yield could be achieved by using a watered down version of the gene. However, this would result in a decrease in the amount of fat and protein content.
According to Dr Vilkki, Finnish Ayrshire cattle illustrate well the benefits that the newly located gene can have on milk quality: In 2002 the annual yield of the Finnish Ayrshire cow was over 7000 kilos with fat and protein content amounting to over 4 per cent 3 per cent respectively.
MTT Agrifood Research Finland continues to coordinate fine mapping activities in genes under the Fifth Framework Programme (FP5) in a project called MASTITIS RESISTANCE, which aims at finding methods to eradicate mastitis, among European cattle herd.
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