Evaluation of Tear Secretion by Phenol Red Thread Test in Holstein Cows

Abstract

This study aimed to measure the normal physiological tear production of Holstein cows with the phenol red thread (PRT) test to determine the reference value specific to this test and to examine the effect of the number of births, age and seasonal air temperature on the amount of tear production. The study was performed on 50 Holstein cows aged 3-7 years in two groups. The PRT test was performed in group 1 in January and in group 2 at the end of May. The age and birth numbers of all animals were recorded. The mean amount of tear secretion for all Holstein cows (n = 50) was 32.90 +/- 0.73 mm/15 sec. The mean value was 34.47 +/- 1.28 mm/15 sec. for group 1 (n = 23) and 31.55 +/- 0.73 for group 2 (n = 27). When the seasonal temperature increased from 12 degrees C to 20 degrees C, the difference in the mean amount of tear production between group 1 and group 2 was statistically significant (P < 0.05). Although there was a tendency for the amount of tears produced to increase with the increase in the number of births, it was not statistically significant (P> 0.05). Similarly, the decrease in the number of tears with increasing age was not statistically significant (P > 0.05). This study determined reference values for tear secretion in healthy Holstein cows with the PRT test. Higher PRT scores were recorded in winter than in spring (P < 0.05), and the change in PRT values was not significant as the number of births and age increased (P > 0.05).