The method used to impure cattle breeds is by taking care of the new ones which take birth. by feeding them with good and nutritious food, by inoculating them and by timely medical checkup, the breeds of the cattle can be improved. 
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He most commonly used method for improving cattle breeds is cross - breeding because through cross breeding we can get the desired qualities in a particular cattle , thus improve the cattle breeds.Hope this helps you..!!!Cheers..!!!! :)
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