Further Studies in Abnormal Blackening of Feathers of Vitamin D Deficient Chicks1

^"- * (1946) observed that the feeding of a vitamin D deficient diet resulted in ab-normal blackening in the feathers of New Hampshire chicks. McGinnis, Kosin and Decker (1947) confirmed these findings. To further the investigation, various ex-periments were undertaken to study the blackening as affected by diet, thyroid, and breed. EXPERIMENTAL Three approaches were made to the problem. In the first series (dietary ap-proach), six lots of New Hampshire chicks were fed Diet 1, vitamin D deficient (Table 1), with various levels of vitamin D. In the second series (hormone ap-proach) seven lots of New Hampshires were placed on various diets to study the effect of thyroxine and certain mineral deficiencies on the blackening; see Table 1 for details. In the third series (genetic approach) breeds of different genetic pat-terns were placed on the D deficient diets. Day-old New Hampshire chicks were used, unless otherwise indicated, and were banded, placed in batteries, weighed weekly and fed the rations shown in Tabl