In an effort to produce a deficiency of vitamin B12 a total of 70 pigs were fed a purified diet containing soybean alpha protein in place of casein. One group of animals was started on the diet at 2 to 7 days of age. A second group began at 21 to 28 days of age. Methionine, iodinate casein, desiccated thyroid and pteroylglutamic acid were added to the diet of certain animals and! omitted from the diet of other pigs. In addition, 9 pigs were gastrectomized. Forty-three of the animals survived for a sufficiently long period of time for adequate evaluation of the results of the experiment.

Severe liver damage was observed in 24 of the 25 animals autopsied. The only animal not showing liver damage received vitamin B12 from the beginning of the experiment. Necrosis of the liver cells, fatty infiltration, or both, occurred in the presence of a high fat diet containing apparently adequate amounts of protein, choline, vitamin E and methionine. These pathologic changes were apparently prevented but not reversed by the administration of vitamin B12.

Growth of the animals on the above diets without added vitamin B12 was retarded as compared with the growth of animals on the same diet supplemented with this vitamin. The administration of vitamin B12 to the deficient animals resulted in rapid growth.

Of the 39 animals not receiving vitamin B12 13 failed to develop anemia, 16 developed a mild anemia and in 10 a moderately severe anemia was present. When present the anemia was normocytic and in 24 pigs was accompanied by a moderately severe neutropenia. Differential cell counts on the sternal marrow were normal except for a slight increase in the proportion of normoblasts. These hematologic alterations were neither consistently or completely corrected by the administration of vitamin B12 in spite of the fact that definite and sometimes marked reticulocyte increases followed.

When methionine deficiency was associated with vitamin B12 deficiency, anemia appeared to be more severe.

The administration of aureomycin, an "animal protein factor," did not stimulate growth and failed to induce a hemopoietic response.

There was no macrocytic anemia, the bone marrow was not megaloblastic, and neurologic disturbances or morphologic alterations in the neutrophils were not observed.

These results are in contrast to those obtained in pigs with an experimentally produced deficiency of pteroylglutamic acid. Such animals develop macrocytic anemia, leukopenia and a macronormoblastic type of bone marrow.

It is not possible to give with any assurance the reason why megaloblastic anemia was not produced in the "B12-deficient" animals. This may have been due to the fact that (1) the deficiency was not sufficiently severe to result in such a change in the hemopoietic system; or (2) because pteroylglutamic acid prevents the development of megaloblastic anemia even in the absence of vitamin B12.

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