Lacrimal Secretion Variation and Menace Response Appearance in Healthy Standardbred Foals From Birth to Four Weeks of Age.

This study assesses lacrimal secretion in healthy foals within 48 hours after birth and evaluates their variations in lacrimal secretion and menace response appearance during the first month of life. A total of 31 Standardbred foals were evaluated. Foals were housed with their dams in 4 × 4 m boxes throughout the study. A complete ophthalmic examination was performed for each animal enrolled in the study, including the foals' dams which were used as a control group to compare the lacrimal secretion of foals at birth with that of adult horses. In foals, the Schirmer Tear Test I (STT I) and menace response were evaluated within 48 hours after birth (T0) and weekly for a total of four times (T1, T2, T3, and T4). In mares, the STT I was evaluated once, before delivery. The Schirmer Tear Test I results of 11 out of 31 dams were excluded because of signs of ocular adnexa inflammation which might otherwise have influenced lacrimal secretion. At T0 STT I values in foals (19.11 ± 2.49 mm/min) were lower than those of their dams (23.20 ± 1.83 mm/min). In addition, the mean STT I in foals decreased during the study period and reached its nadir at T3 (16.84 ± 2.33 mm/min). None of the foals showed a menace response at any observation point. In conclusion, within 48 hours after birth, healthy Standardbred foals show a lower lacrimal secretion than their dams, and tear secretion does not seem to increase during the first month of life. In this period, poor lacrimation associated with the absence of an evident menace response might be predisposing factors for developing corneal ulcers.