Page 1046 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

978 SECTION | XIV Poisonous Plants

VetBooks.ir day free gossypol for dogs. However, dietary gossypol camara, monkshood Aconitum napellum, and milkweed
$ 350 400 ppm in mature dairy goats; (4) #6 mg/kg/
Asclepias spp.).
intake alone is insufficient for a definitive diagnosis.
Tissue gossypol levels are supportive of gossypol
exposure. Liver and kidney samples are typically the most PREVENTION
diagnostically useful. However, definitive levels associ-
ated with toxicity have not been systematically estab- The single best method of prevention is to accurately
lished in domestic animals. measure concentrations in feed and limit the dietary
intake. The US FDA and the European Union have estab-
lished maximum acceptable levels of gossypol in feeds.
US 21CFR172.894 states that cottonseed products
Differential Diagnosis
intended for human consumption must contain not more
Important differential diagnoses include: (1) cardiotoxic than 450 ppm of free gossypol. The European Union
ionophoric antibiotics (e.g., monensin, lasalocid, salino- directive 2002/32 states that the maximum free gossypol
mycin, narasin) and ammonia; nutritional or metabolic concentrations for cottonseed meal is 5000 ppm and for
disorders (e.g., selenium, vitamin E, or copper defi- cake is 1200 ppm. For complete feedstuffs, the maximum
ciency); infectious diseases; noninfectious diseases (e.g., permissible level for laying hens is 20 ppm, for piglets is
pulmonary adenomatosis, emphysema); mycotoxicoses 60 ppm, for adult pigs is 60 ppm, for rabbits is 60 ppm,
caused by Fusarium-contaminated grain; and toxicoses for other poultry is 100 ppm and is 500 ppm for cattle,
caused by plants with cardiotoxic and other effects sheep, and goats.
(English yew Taxus baccata, Japanese yew Taxus cuspi- A selected summary of techniques used to reduce gos-
data, laurel Kalmia spp., azalea Rhododendron spp., ole- sypol exposure is shown in Table 68.6. Critically, ammo-
ander Nerium oleander, yellow oleander or yellow-be-still niation of cottonseed meals should be avoided since it
tree Thevetia peruviana, purple foxglove Digitalis increases gossypol bioavailability. Immunoprotection via
purpurea, lily-of-the-valley Convallaria majalis, dogbane vaccination of a bovine serum albumin-gossypol conju-
Apocynum spp., coffee senna Senna occidentalis, bracken gate has been attempted. Despite being immunogenic, the
fern Pteridium aquilinum, white snakeroot Eupatorium procedure increased the susceptibility to gossypol-induced
rugosum, death camas Zygadenus spp., lantana Lantana hepatotoxicity (Fonseca et al., 2013).

TABLE 68.6 Selected Methods of Reducing the Risk of Gossypol Poisoning

Method Comments
Heat treatments Heat treatment likely increases protein binding. However there is limited evidence that the conjugates that are
Roasting formed can be broken down in the ruminant and chicken digestive tract, releasing free gossypol
Extrusion
Irradiation Mechanism of the effect is unknown. It is assumed that irradiation results in gossypol molecule aggregation, or
Gamma irradiation cross-linking, fragmentation or oxidation
Electron beam
irradiation
Fungal fermentation These techniques are largely experimental and appear to be safe. However these products are not yet
Aspergillus niger commercially available
oryzae
Candida tropicalis
Saccharomyces
cerevisiae
Geotrichum
candidum
Nutritional Dietary iron supplementation is a classic technique that relies upon complexation of gossypol and iron in the
supplementation gut. The recommended rate of supplementation is 1 mol of iron for each mol of gossypol in the feed
Ferric sulfate
Sodium selenite Supplementation of sheep with 1 mg of sodium selenite/day reduced the effects of gossypol on male fertility
Vitamin E parameters
Supplementation of cattle with 4000 IU/day reversed the effects of gossypol on male fertility parameters and
the effects on the erythron