Measuring eyeball recession and degree of skin tent on the neck are two good ways to assess dehydration in neonatal calves, says Geof Smith, assistant professor of ruminant medicine at North Carolina State University. With the eyeball method, place your finger on the bottom eyelid and gently roll it down away from the eye. If a visible gap between the eyelid and the eyeball exists, the calf is dehydrated and needs electrolyte therapy. The larger the gap is, the greater the dehydration. The skin-tent method is fairly well understood, but not always interpreted accurately.