Nutritional deficiency in poultry is caused due to

Nutritional deficiency in poultry is caused due to Vitamin-A.
Xerophthalmia is the Vitamin A deficiency in poultry, that is rare in commercial poultry but seen in backyard poultry occasionally.
The main symptoms are drooling of mucus from the mouth, corneal opacity, conjunctivitis, ruffled feathers, decreased weight gain and egg production.