Page 1000 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

932 SECTION | XIV Poisonous Plants

VetBooks.ir techniques may be valuable. A notable use of physical provide sufficient leafy material to minimize the eat-
removal of poisonous plants over relatively large land
ing of twigs and branches, (3) follow a set feeding
areas is the use of “scalping” in the wheat belt of
routine; it is common to cut two to three day s supply,
Western Australia. “Scalping” involves the removal of but daily cutting may be necessary in summer to avoid
all topsoil that may contain Gastrolobium sp. seeds leaves withering; as the drought progresses, the foliage
and replacing the topsoil with new poison pea-free on uncut scrub dries out and fresh scrub may need to
soils sourced from elsewhere. This extreme and expen- be cut daily, (4) while stocks are strong, cut the scrub
sive technique has been historically used with some most distant from water; then cut closer scrub, (5) if
success. acceptance is poor, spraying with a molasses-water
Use of herbicides: Again, because of the sheer physi- mixture may increase intakes, but some trees in every
cal size of livestock properties in the semiarid and arid stand of scrub are unpalatable; generally, older mulga
regions of Australia, such methods are often uneco- (A. aneura and related Acacia sp.) trees are preferred
nomic. Herbicide use may, in fact, increase the toxic- to young ones, (6) pulling with a chain or bulldozing
ity (and in some cases the palatability) of some plants. can reduce acceptance because of high dust levels, (7)
Use of biocontrol agents: A number of biocontrol supplementation with protein nitrogen (e.g., cottonseed
agents are being developed in Australia for the control meal), nonprotein nitrogen (e.g., urea), sulfur (e.g.,
of introduced poisonous plants, notably for Paterson’s sulfate of ammonia) and phosphorus (e.g., dicalcium
curse. Biocontrol agents are unlikely to be developed phosphate) has been found to be beneficial during
for indigenous plants. scrub feeding, particularly during pregnancy and lacta-
Sheep, cattle, and goats are somewhat more tolerant of tion (stimulate the rumen function and increase feed
some poisonous plants than are other livestock. The intakes); irregular supplementation with molasses
use of goats to control Gastrolobium sp. and the use of appears to reduce the risk of impaction, (8) consider
sheep on pastures containing heavy growths of the long-term environmental effects of pulling scrub;
Paterson’s curse and heliotrope are common examples. leave strips of trees for regeneration, wildlife protec-
However, some stock losses are often encountered in tion and the like, (9) often sheep and cattle will lose
these types of enterprises, and they require careful their appetite for scrub after a couple of months, so
management. other sources of feed must be available, (10) stock
Supplementary feeding (including the use of safe, but will eat some trees, but will leave others of the same
not normally consumed native plants) during drought species, on the same soil type; seek local knowledge
is also commonly and successfully used to avoid the in determining which trees and shrubs are suitable for
effects of drought and poisonous plants on livestock. feed in your district; observing the scrub that stock
This has led to the common practices of drought lot- regularly eat and trees that have a clear browse line
ting and scrub feeding—the creation of temporary fee- can also aid in determining palatable species; (11)
dlots utilizing native plants in order to maintain key when toxicity has occurred, it has often involved
livestock. Various relevant state government depart- young, newly emerged leaves, and (12) heavy stock
ments commonly maintain registers of safe native losses can occur when weak cattle “chase the green
plants that can be used for drought feeding. The leaves pick” following drought breaking rain; if possible,
of Acacia aneura (mulga) have historically been confine weak cattle and continue to feed scrub until
extensively used as drought feed for sheep in the arid, sufficient grass has grown for them to get their fill
central zone of Australia. Although the plant is effec- without expending valuable energy. Notably, “mulga
tive for this purpose, consumption results in nutritional apples,” the common wasp-induced galls on mulga
melanosis of the liver and kidneys of sheep (com- trees (A. aneura), are edible (a well-known bushfood
monly called “black liver” or “mulga liver” or “bore traditionally used by the Arrente language peoples of
water liver”). The pigment accumulation is benign and Central Australia), sweet tasting, and highly nutritious.
the animals suffer no adverse effects, but the liver and Feeding information on common fodder trees is pro-
kidneys from affected animals cannot be sold for vided in Table 63.1. These plants should be preserved
human consumption for aesthetic reasons, resulting in and encouraged in drought prone areas of Australia
some financial loss. Another known problem with this (except for those that have been declared as noxious
system is gastric impaction, which often results from weeds/invasive plants).
cutting too little of the leaf material (i.e., forcing the A long-standing and well-proven strategy to reduce
animals to eat twigs and branches) and/or allowing the the risk of stock losses due to drought conditions and/
plant material to dry out and/or the animals not drink- or when poisonous plants are present has been to phys-
ing enough water. Current recommendations for scrub ically relocate livestock from properties/regions that
feeding include: (1) cut only one species at a time, (2) are entering into drought conditions to geographic