Objective clinical examination of poultry as illustrated by the comparison of chickens with different vitamin A status.

One day old pullets derived from marginally vitamin A deficient laying hens were fed diets containing either adequate or marginal amounts of vitamin A. At the age of 34 days, animals fed the diet low in vitamin A had group mean plasma concentrations of retinol which were one tenth the mean plasma concentrations of controls. When compared with their controls, the deficient animals displayed body weights which were on average 16% less. Of 20 pullets per dietary group one control animal and 9 deficient animals died by the age of 34 days. At the age of 29 days, control (n = 16) and deficient chickens (n = 11) were examined clinically by assigning scores to a number of parameters. Three assessors carried out the examination independently. The birds were presented for examination at random and their treatment groups were not disclosed to the assessors. Out of 26 parameters assessed quantitatively per individual animal, only three parameters discriminated between control and deficient chickens. Deficient animals grew poorly, had a hunched up posture and increased fluid content in faeces. Classical signs of chronic vitamin A deficiency in domestic fowl such as bone deformities, keratinization of the tongue and decreased transparency of the cornea were not observed.