Corneal sensitivity in healthy bovine calves

Objective: To evaluate corneal sensitivity as measured by the corneal touch threshold in healthy bovine calves. Animals Studied: Twelve clinically normal male calves with predominantly Holstein genetics and a median age of 76.5 days (range, 67-92 days). Procedures: Corneal touch threshold (CTT) of the central cornea was measured in both eyes of each calf using a Cochet-Bonnet aesthesiometer. Results: The mean ± standard deviation corneal touch threshold of all eyes was 1.33 ± 1.1 g/mm² (range, 0.62-66.15 g/mm²), corresponding to a filament length of 34.56 ± 8.02 mm (range, 14-47.5 mm). There was no significant difference between fellow eyes. Conclusions: Cochet-Bonnet aesthesiometry was well tolerated in all 12 calves using a modified head restraint. Calves in this study may have a relatively sensitive central cornea compared to adult cattle and some other species; however, wide variation among individuals and eyes may be possible. Studies utilizing larger calf populations are necessary to establish reference ranges.