The influence of dietary carotene on the mortality pattern of fowl with some observations on the influence of condensed fish solubles

An investigation was carried out on the incidence of mortality from avitaminosis‐A and the depression in egg production consequent upon feeding laying stock with vitamin‐A‐deficient rations, using stock known to be susceptible to fowl paralysis and avian leucosis and in which the death rate from these diseases was high. This was decided upon as there have been many cases recorded where the liver of birds succumbing to these diseases has contained amounts of vitamin A greatly below normal, and the suggestion has been made that a low level of dietary vitamin A might promote increased mortality from these diseases. No consistent correlation was found between deficiencies of dietary vitamin A and the incidence of paralysis and avian leucosis. With low levels of carotene (500 i.u. of vitamin A/lb.) a marked death rate from avitaminosis‐A did not occur until 5 to 8 months after feeding the deficient diet which was begun at the 31/2‐month‐old stage. Egg production showed an initial delay of between 4 and 6 weeks, but a marked depression was not manifest until well into the season. Increase of mortality from avitaminosis‐A and further depression of egg production occurred when a vitamin‐A‐deficient diet was supplemented with fish solubles, but this was not apparent with diets having high levels of vitamin A. It is tentatively suggested that the destruction of vitamin A by animal protein may be caused by some factor in the water‐soluble part of animal protein.