Protecting Livestock from Blue-Green Algae Poisoning
Livestock owners are being urged to be vigilant about the potential dangers of blue-green algae, particularly during the warmer months when algal blooms are more likely to occur. Blue-green algae, or cyanobacteria, are bacteria that can grow rapidly under certain conditions, particularly when water is warm and enriched with nutrients like phosphorus or nitrogen. These blooms can appear as green, paint-like surface scum in the water but may also appear reddish-purple or brown. It can be challenging to distinguish blue-green algae from other, less toxic algal species, making identification difficult for farmers.
While blue-green algae may be visually unremarkable, it can produce toxins that pose serious risks to livestock, pets, and even humans. These toxins can affect the liver, nervous system, and skin, and can be fatal if ingested. Livestock that drink contaminated water may die quickly, often with multiple animals affected at once. In some cases, animals may continue to suffer or die over a prolonged period, while in less severe cases, there may be productivity losses, such as decreased milk yield in dairy cattle. If a suspicious bloom is found, it is critical for farmers to remove their animals from the contaminated water and provide an alternative safe water source.
To mitigate the risks of blue-green algae poisoning, livestock owners are advised to develop a management plan for water availability in the event of an algal bloom affecting their primary water supply. This plan should include calculating the water requirements for livestock, identifying alternative water sources on the property, and considering medium-term strategies such as improving water reticulation systems or treating affected water. In cases where the primary water source remains unsafe, farmers may need to consider agisting their stock elsewhere until conditions improve.
Blue-green algae can produce a range of harmful toxins, including neurotoxins, liver toxins, and skin allergens. The severity of poisoning depends on various factors, including the amount of toxin ingested, the susceptibility of the animal, and whether the animal has recently eaten, as food in the gut can help mitigate the effects of the toxin. All animals, including livestock, pets, and humans, are at risk of poisoning from blue-green algae. Sheep, in particular, are more vulnerable as they are more likely to drink from the dam edges, where algae concentrations are highest, while cattle often wade deeper into the water, away from the more toxic surface layers.
Toxicity levels can change rapidly, with toxins increasing as the bloom ages or begins to die off. In some cases, toxins can persist in the water for months after the bloom has disappeared, with sun-dried algal mats remaining toxic for up to five months. Livestock that drink water contaminated by these toxins may show signs of poisoning that vary depending on the type of toxin involved.
When neurotoxins are present, affected animals may show symptoms such as muscle tremors, staggering, and convulsions, with death occurring within 24 hours of the first signs. Liver toxin poisoning may result in ill-thrift, scouring, jaundice, and photosensitisation, where pale skin, particularly around the head, becomes swollen, red, and develops scabs. Deaths from liver toxins may occur 1–2 weeks after ingestion. In both cases, if blue-green algae poisoning is suspected, it is crucial to remove livestock from the contaminated water supply immediately. Although there is no specific treatment for the condition, activated charcoal or bentonite can be administered to prevent further absorption of toxins, but this is an expensive option best reserved for valuable animals.
There are also several diseases that can present with similar symptoms to blue-green algae poisoning, including anthrax, pulpy kidney, lupinosis, and photosensitisation. Anthrax is a reportable disease with human health risks, so any sudden and unexplained deaths in livestock should be investigated by a veterinarian. If you suspect your livestock has been affected by blue-green algae, it’s essential to contact a veterinarian, the Department of Primary Industries and Regional Development, or the Emergency Animal Disease hotline on 1800 675 888 for advice and support.
Preventing blue-green algae blooms is possible by regularly monitoring water supplies that are susceptible to algae growth. Early detection and treatment are critical in managing algae proliferation and reducing the risk of poisoning. By proactively managing water sources and having a plan in place, farmers can protect their livestock and minimize the risks associated with blue-green algae.
Source: BeefCentral.com & agric.wa.gov.au