Heinemann et al. (1946) reported that the pig can utilize stored thiamin over a long time, as 56 days was required for the pigs to lose their appetites after beginning a thiamin-deficient diet. Death has been reported 74 days after pigs began a thiamin-free but otherwise adequate diet (Loew, 1978). For young pigs, severe thiamin deficiency has resulted in death at the age of three to four weeks.
First signs of thiamin deficiency in pigs are reduced feed consumption and vomiting, with a sharp reduction in weight gains (Van Etten et al., 1940; Miller et al., 1955; Peng and Heitman, 1973). Functional and structural cardiac changes are the main findings in experimentally deficient swine; in contrast to clinical reports, nervous system lesions were not detected (Follis et al., 1943). Electrocardiographically demonstrable changes in heart tissue are also seen, with enlarged hearts obtained from pigs receiving thiamin-deficient diets (Illus. 2). The heart can be flabby, as reported by Van Etten et al. (1940), with myocardial degeneration. On microscopic examination, it is possible to recognize inflammations and necrotic changes in the myocardial fibers.