Endogenous toxins and mycotoxins in forage grasses and their effects on livestock

Abstract

Plant toxins are the chemical defenses of plants against herbivory. Grasses have relatively few intrinsic toxins, relying more on growth habit to survive defoliation and endophytic fungal toxins as chemical defenses. Forage grasses that contain intrinsic toxins include Phalaris spp. (tryptamine and carboline alkaloids), sorghums (cyanogenic glycosides), and tropical grasses containing oxalates and saponins. Toxic effects of these grasses include neurological damage (Phalaris staggers), hypoxia (sudangrass), saponin-induced photosensitization (Brachiaria and Panicum spp.), and bone demineralization (oxalate-containing grasses). Endophytic toxins in grasses include ergot alkaloids in tall fescue and tremorgens (e.g., lolitrem B) in perennial ryegrass. Lolitrems cause neurological effects, producing the ryegrass staggers syndrome. Annual ryegrass toxicosis is caused by corynetoxins, which are chemically similar to tunicamycin antibiotics. Corynetoxins are produced by Clavibacter bacteria that parasitize a nematode, Anguina agrostis, that may infect annual ryegrass. Corynetoxins inhibit glycoprotein synthesis, causing defective formation of various blood components of the reticulo-endothelial system. Another mycotoxin in ryegrass is sporidesmin, which causes liver damage and secondary photosensitization (facial eczema). Fusarium toxins such as zearalenone and trichothecenes also occur in forage grasses. Kikuyugrass poisoning results in severe damage to the ruminal epithelium and omasal mucosa, and neurological signs. The causative agent, which may be associated with army worm predation of the grass, has not been identified. The properties and significance of these toxins are reviewed.

Mycotoxins in cattle feeds and carry-over to dairy milk: A review

“…The level of contamination of (cold season) grasses shows significant geographical differences (Cheeke 1995) and is gaining increasing attention.…”

Lolitrem B Residue in Fat Tissues of Cattle Consuming Endophyte-Infected Perennial Ryegrass Straw

“…Toxicoses in livestock caused by endophyte-infected grasses are well known as ryegrass staggers 1 and fescue toxicosis. 6 Lolitrem B, found in Neotyphodium lolii-infected perennial ryegrass, is the predominant toxin responsible for ryegrass staggers.…”

“…1 Corresponding Author: Shigeru Miyazaki, Toxico-Biochemistry Section, National Institute of Animal Health, Tsukuba, Ibaraki 305-0856, Japan.…”

Fall Panicum (Panicum dichotomiflorum) Hepatotoxicosis in Horses and Sheep

“…1 However, several reports document hepatogenous photosensitization or hepatopathies in grazing animals after ingestion of various Panicum, 2-6 Brachiaria, 7,8 Tribulus, 9,10 and Narthecium 11 grass species. These plants contain steroidal saponins, 4,8,[10][11][12][13][14][15] and affected ruminants often develop bile crystals composed of the calcium salts of steroidal saponin glucuronides.…”