$affiliateModel = new AffiliateUser();
   $metaData = $affiliateModel->info('metadata');

$first_name = new Zend_Form_Element_Text('first_name');
  $first_name->setRequired(true)
            ->addFilter('StringTrim')
            ->addValidator('StringLength', false, array(2, $metaData['first_name']['LENGTH']))
            ->setDecorators(array('ViewHelper', 'errors'));

->addValidator('StringLength', false, array(2, $metaData['first_name']['LENGTH']))