The Phytolaccaceae includes Phytolacca americana (syn. P. decandra), the pokeweed, the leaves of which are eaten as a vegetable after boiling. The fruits have been reported to be toxic to children (Burrows and Tyrl, 2001). Livestock, especially pigs, are known to be poisoned by eating the roots, and extreme irritation can be caused in humans by inhalation of root powder. The berries and roots have been shown to contain saponins (Kang and Woo, 1980).
Ponderosa pine (Pinus ponderosa) is a member of the Pinaceae that has frequently produced third-trimester abortion in pregnant cattle grazing the needles (Cheeke, 1998). Anecdotal evidence indicates that under rangeland conditions, as little as 1 lb of the green needles can induce the effect in as little as 24 hours with virtually the whole herd being affected. The syndrome is generally known as “pine needle abortion,” but is more properly described as premature parturition since the calves are born live but generally do not survive without exceptional supportive treatment (Cheeke, 1998). Isocupressic acid (a diterpene), together with its acetyl and succinyl esters, has been shown to be the agent responsible for the observed effects by feeding trials with the purified compound; the esters are rapidly hydrolyzed to the acid in the rumen (Cheeke, 1998). Lodgepole pine (P. contorta) and Jeffrey pine (P. jeffreyi) also contain significant amounts of isocupressic acid, the needles of which have been reported to cause abortion (Garland and Barr, 1998). A number of other Pinus (Pinaceae) and Juniperus (Cupressaceae) species contain lower levels of the isocupressic and related diterpene acids and may be capable of inducing pregnancy disorders (Garland and Barr, 1998).
The Poaceae encompasses many cultivated species used as a staple food source as grains or flour. Both cultivated and wild grasses are used as forage for livestock, and poisoning episodes are not uncommonly observed in certain situations, especially when a single species is grazed almost exclusively. Toxic levels of nitrates, strongly influenced by factors such as soil type and environmental conditions, can occur in Avena sativa (oats), cultivated and wild Sorghum species, Secale cereale (rye), and Zea mays (corn) (Kellerman et al., 1988). Nitrate levels exceeding 1.5 percent potassium nitrate equivalents are considered to be fatal to livestock (Kingsbury, 1964). In the gut, nitrate is reduced to nitrite, which is approximately 10 times more toxic than nitrate, and ultimately to ammonia (Kellerman et al., 1988).
Cultivated Sorghum species are produced either as grain sorghums (milo) or forage sorghums. All of these, and also wild species, contain cyanogenic glycosides, in particular the glucoside dhurrin (Cheeke, 1998).