Oak poisoning
Like other oak species, blue Japanese oak may have detrimental effects on animal health. In oak poisoning, clinical signs occur 3-7 days after consumption of large quantities of young oak leaves in the spring, or green acorns in the fall. Outbreaks have occurred when hungry animals have gained access to fallen trees associated with a recent storm. Mortality as high as 70% has resulted. In pregnant cows, the consumption of acorns during the second trimester of pregnancy resulted in malformed calves and abortions. The toxicity could be due to pyrogallol, gallotannins, polyhydroxyphenolic compounds, or their metabolites produced by microbial hydrolysis in the rumen, which bind and precipitate proteins, and result in general and renal dysfunction (Blakley, 2013).
Blue Japanese oak seeds contain high levels of tannins that may be toxic to animals and humans. It is recommended to wash them thoroughly before using them (Orwa et al., 2009). When fed at high levels, oak (Quercus incana) leaves produce toxic effects (Lohan et al., 1983; Makkar et al., 1991). Their tannin content increases with maturity but the protein precipitation capacity of these tannins is among the lowest in the genus Quercus (Makkar et al., 1991). Incorporation of Quercus incana leaves into mixed rations above 14% (on dry weight basis) has been shown to have adverse effects (Lohan et al., 1983). Feeding at higher levels or as the sole feed resulted in oak poisoning (Makkar et al., 1991). Although growing conditions are known to influence tannin levels, it was inferred that the mature leaves of blue Japanese oak would produce adverse effects even at lower levels of feeding, as the tannin levels in leaves of this species are higher than those of Quercus incana (Lohan et al., 1983). Feeding mature leaves of blue Japanese oak might be more deleterious than feeding younger leaves (Makkar et al., 1991). Mixed beef cattle experimentally fed blue Japanese oak leaves showed clear clinical and histological signs of poisoning, resulting in the death of 2 animals out of 4 (Hwang et al., 1991a; Hwang et al., 1991b).