Ocular abnormalities associated with hypovitaminosis A in Hanwoo calves: a report of two cases

KANG, Seonmi; PARK, Chanho; SEO, Kangmoon

The normal serum level of vitamin A in calves is reported to be between 25 and 35 µg/dl; a level below 20 µg/dl is classified as hypovitaminosis A. The reference range for adult cattle is reported to be between 40 and 50 µg/dl [7] . In this study, the serum vitamin A concentrations of the two affected cattle were substantially below normal values. The minimal duration of vitamin A deficiency capable of inducing papilledema has been reported to be six to eight weeks, based on a previous study on experimentally induced hypovitaminosis A [3] . Papilledema, if untreated, can progress to optic nerve atrophy, which leads to permanent vision loss [3] . Both calves in this study had papilledema, accompanied by vision loss. Changes in the optic nerve and the optic nerve head have been reported to be caused by necrosis resulting from stenosis of the optic canal and an increase in cerebrospinal fluid (CSF) pressure in hypovitaminosis A [3, 4] . In growing animals, an increase in CSF pressure is a significant event brought about by hypovitaminosis A [1] ; faulty absorption and increased resistance to outflow are the possible causes for this increase [1] .