ESSENTIALITY OF CHOLECALCIFEROL IN THE DIETS OF RAINBOW-TROUT (SALMO-GAIRDNERI)

1. 1. Vitamin D3 was found to be essential in the diet of rainbow trout. 2. 2. Vitamin D3 deficiency in rainbow trout was characterized by a marked decrease in weight gain and feed efficiency, lethargy and anorexia, the clinical manifestations of tetany without hypocalcaemia. an increase in the lipid content of carcass, white muscle and liver, and increased carcass dry matter. 3. 3. Unlike mammals, bone and blood mineral stores appeared unaltered in vitamin D3 deficient rainbow trout. 4. 4. With trout maintained in water containing 30ppm of calcium, increasing the level of dietary calcium from 0.36% to 1.1% increased the amount of white muscle lipid and decreased the kidney magnesium levels, but exerted no effect on weight gain or feed efficiency, regardless of vitamin D3, status. 5. 5. Rainbow trout receiving feed containing 1000 i.u./kg of vitamin D3 showed no detectable amounts of 25-hydroxycholecalciferol or 24R. 25-dihydroxycholecalciferol in their blood plasma. © 1979.