Effect on Growth and Efficiency of Food Utilization of Quantity of Protein and Vitamin B12 Supplementation

Certain nutritional and therapeutic values of liver extracts had been demonstrated experimentally again and again prior to 1948. Most of the early studies were related mainly to hematopoiesis (Subbarow et al., 1945), yet others were concerned with their capacity to augment the growth promoting properties of rations for chicks (Nichol et al., 1948), mice (Bosshardt et al., 1946) and rats (Jaffe, 1946; Sporn et al., 1947; Ershoff, 1947; Zucker, 1948). More recently the beneficial effects of liver extracts for hogs and poultry have been attributed to an unknown factor (s) tentatively identified as the animal protein factor, APF. The identity of the APF is unknown. However, one of the markedly effective constituents of APF concentrates is vitamin B12