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Vitamin A deficiencies can occur due to low dietary intake of retinol, with concurrent diseases affecting absorption of dietary fat (e.g. [[Protein Losing Enteropathy|protein-losing enteropathy]]) or with abnormal storage and transport of retinol (i.e.[[:Category:Liver - General Pathology|liver disease]]).

Vitamin A deficiencies can occur due to low dietary intake of retinol, with concurrent diseases affecting absorption of dietary fat (e.g. [[Protein Losing Enteropathy|protein-losing enteropathy]]) or with abnormal storage and transport of retinol (i.e.[[:Category:Liver - General Pathology|liver disease]]).

====Dogs:====  

====Dogs:====  

Puppies fed Vitamin A deficient diets have poor growth rates and develop defective remodelling of bone during active growth<ref name="NRC"/>, especially the bones of the cranium, which can result in [[Ear - Anatomy & Physiology#Deafness|deafness]]<ref>Mallenby E. The experimental production if deafness in young animals by diet. J Physiol 1938;94:380-398.</ref>. Adult dogs fed Vitamin A deficient diets experience '''anorexia, weight loss, squamous metaplasia of mucus secreting cells that can result in xerophthalmia (dry eye) and increased susceptibility to [[Pneumonia Overview|pneumonia]]'''<ref>Russell WC and Morris ML. Vitamin A deficiency in the dog. Experimental production of vitamin A deficient condition. JAVMA 1939;95:316-320.</ref>. Cutaneous hyperkeratosis and skin lesions are also associated with Vitamin A deficiency in adult dogs<ref>Ihrke PJ and Goldschmidt MH. Vitamin A-responsive dermatosis in the dog. JAVMA 1983;182:687-690.</ref>. Adult females fed inadequate levels of Vitamin A during gestation have an increased risk of foetal abnormalities<ref name="NRC"/>.  

Puppies fed Vitamin A deficient diets have poor growth rates and develop defective [[Bone & Cartilage Development - Anatomy & Physiology|remodelling of bone]] during active growth<ref name="NRC"/>, especially the bones of the cranium, which can result in [[Ear - Anatomy & Physiology#Deafness|deafness]]<ref>Mallenby E. The experimental production if deafness in young animals by diet. J Physiol 1938;94:380-398.</ref>. Adult dogs fed Vitamin A deficient diets experience '''anorexia, weight loss, squamous metaplasia of mucus secreting cells that can result in xerophthalmia (dry eye) and increased susceptibility to [[Pneumonia Overview|pneumonia]]'''<ref>Russell WC and Morris ML. Vitamin A deficiency in the dog. Experimental production of vitamin A deficient condition. JAVMA 1939;95:316-320.</ref>. Cutaneous hyperkeratosis and skin lesions are also associated with Vitamin A deficiency in adult dogs<ref>Ihrke PJ and Goldschmidt MH. Vitamin A-responsive dermatosis in the dog. JAVMA 1983;182:687-690.</ref>. Adult females fed inadequate levels of Vitamin A during gestation have an increased risk of foetal abnormalities<ref name="NRC"/>.

 

====Cats:====  

====Cats:====  

Feeding Vitamin A deficient diets to pregnant queens can result in increased risk of '''spontaneous abortions, foetal resorptions, and [[Cleft Palate|cleft palate]] in kittens'''<ref name="NRC"/>. Adult cats fed Vitamin A deficient diets will also experience weight loss and squamous metaplasia of mucous secreting cells<ref name="NRC"/>, with xerosis and associated corneal keratinization and vascularization.

Feeding Vitamin A deficient diets to pregnant queens can result in increased risk of '''spontaneous abortions, foetal resorptions, and [[Cleft Palate|cleft palate]] in kittens'''<ref name="NRC"/>. Adult cats fed Vitamin A deficient diets will also experience weight loss and squamous metaplasia of mucous secreting cells<ref name="NRC"/>, with xerosis and associated corneal keratinization and vascularization.