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Nature 00034.txt

No bull: genes for better milk: Nature Newson 13 january, the US Department of agriculture (USDA) launched a service that allows dairy-cattle breeders to double their chances of selecting the best bulls to sire milk-producing cows. This is the future of animal breeding, says Juergen Richt, a veterinary surgeon at Kansas State university in Manhattan. For a decade, breeders who want to locate the best bull have the animals'semen tested for its DNA, looking for traits linked to milk quality and production. About a year ago, the leading artificial-insemination organizations in the United states and Canada funded a US$1-million research project directed by Curtis Van Tassell a geneticist at the USDA's Bovine Functional genomics Laboratory in Beltsville, Maryland. Working with Illumina Inc. of San diego, California, Van Tassell's team created a microarray chip containing 54,000 genetic markers called single nucleotide polymorphisms, or SNPS, that involve at least a dozen traits, including those known to affect milk quality and production. Using high-throughput analysis, the researchers could then compare the DNA from a young dairy bull against the chip SNPS, telling breeders which bull would be likely to sire calves that were good milk producers. The test costs about $225 and can be done when a bull is born, thus avoiding the $25, 000-50,000 cost of raising a bull for five years to see if it sires good milk-producing offspring. The best bulls become elite breeders, says Van Tassell, The others become hamburger. Previously, DNA tests allowed a typical breeder to select the best bull some 35%of the time, says geneticist Ole Meland, vice-president of Accelerated Genetics in Baraboo, Wisconsin. The new technique identifies the best bull 70%of the time. The US initiative is the first such nationwide programme. Companies in New zealand and The netherlands have set up private services for cattle breeders; and, following the USDA's lead, similar systems are being built by researchers at Aarhus University in Denmark, and in France and Australia.

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