Horizon Organic Holding Corp., the nation's leading producer of organic dairy products, announced today the acquisition of Devon, England-based Meadow Farms Ltd., the leading processor and supplier of organic fluid milk in the U.K. The purchase includes a processing and packaging plant.Meadow Farms, with sales of approximately 16 million British pounds ($24 million at today's exchange rate) for its fiscal year ended May 31, 2000, produces private label organic milk for leading supermarket chains in the U.