Federal investigators are accusing a former Clintonville couple of defrauding the government and two cattle-leasing companies of more than 400-thousand dollars.  The trial for Derek and Kaitryn Van Asten is scheduled to start in mid-May.  They live in Rolfe, Iowa, now.  The Van Astens are accused of getting a series of loans from the Farm Service Agency to buy hundreds of cows for their dairy farm.  Investigators say they sold those cows to commercial cattle buyers as their own property, failing to use the money to buy replacement cows as required by the loan agreement.  Seventy-two transactions are questioned.  The Van Astens are also accused of lying in bankruptcy court about those transactions.