Effects of Low Serum Vitamin A Level on Pupillary Light Reflex in Japanese Black Cattle

Four parameters of pupillary light reflex were investigated from May to December in 2011 to study the effects of low serum vitamin A level on pupillary light reflex in Japanese black cattle during their vitamin A controlled stage. A 2CCD camera was used to acquire the pupillary light reflex images. Constriction amplitude in 1 second, maximum constriction velocity, maximum velocity time and initial pupil roundness were used for pupillary light reflex analysis. Cattle in low vitamin A level period had larger constriction amplitude in 1 second (p=0.001), higher maximum constriction velocity (p=0.016) and thinner resting pupil (p=0.003). This result showed pupillary light reflex analysis can be used as indicators for cattle management during vitamin A controlled stage.