Most promising initial symptom of Vitamin-A deficiency in cows and horses

Most promising initial symptom of Vitamin-A deficiency in cows and horses is Copius lacrymation.
Copius lacrymation is the secretion of tears especially when abnormal or excessive.
Other Vitamin A Deficiencies in Cows and Horses also cause night blindness, watery eyes, bone and muscle growth defects, a dull coat, reproductive problems, and increased susceptibility to disease and infection.