Feasibility of pupillary light reflex analysis to identify vitamin A deficiency in Japanese black cattle

Abstract

To produce beef with a higher marbling standard, Japanese black cattle farmers usually actively attempt to lower the serum vitamin A level in the fattening period to a minimum desired level (about 30 IU/dL). However, early identification of suboptimal vitamin A deficiency in the cattle is important to prevent them from becoming susceptible to contracting serious diseases. In this study, we investigated the feasibility of using Pupillary Light Reflex (PLR) analysis to identify vitamin A deficient cattle during this fattening period. PLRs of 43 cattle were recorded monthly from June 2012 to February 2013 using a 2CCD camera based handheld machine vision system. A new image processing algorithm to segment the pupil from the background was developed. Compared with manually selected results, the root mean square error associated with the constriction amplitude (CA) acquired by the image processing algorithm was only 2.3%, indicating the effectiveness of this algorithm. No significant differences were found between results of CA from fattening cattle in the high (>60 IU/dL) and low (<30 IU/dL) vitamin A period. However, two fattening cattle were identified with severe vitamin A deficiency, because of their weak PLR (CA < 10%). Initial Pupil Roundness (IPR) results showed cattle in a dark environment possessed less-dilated pupils during the vitamin A deficient period (p < 0.05). These results highlight the potential, as well as the limitations of this method. Due to the natural variation of PLR in healthy cattle, monthly measurements are not sufficient to make accurate identification. To realize early identification of severe vitamin A deficiency in fattening cattle, a more frequent PLR measurements regime needs to be explored.