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Lasalocid (aka Bovatec) is a regular additive to cattle feed. It’s used as a preventative for coccidiosis in calves. However, lasalocid toxicity has been a regular cause of disease and death over the years and so we wanted to raise awareness about the potential risk it poses.

How does lasalocid work?

Lasalocid is classed as an ionophore. These substances bind to sodium ions and help move them across cell membranes. Cells normally have a low inner concentration of sodium and they continually pump sodium ions out of the cell to maintain this low level. Lasalocid helps sodium enter cells and subsequently, the cells have to use up energy to pump the sodium back out. The cells eventually run out of energy, and sodium accumulates:, this draws in water and the cells swell up and burst.

While cell death is great in the case of coccidiosis, this end result can also occur in the cells of skeletal and heart muscle if calves are overdosed with lasalocid.

calves with lasalocid toxicity showing opisthotonus

What does lasalocid poisoning look  like?

The presentation of lasalocid poisoning is similar to other diseases, such as Vitamin B1 deficiency and salmonellosis, and so the initial investigation can sometimes be confusing.

Signs of toxicity in calves include:

  • Depression
  • Scouring
  • Weakness
  • Rapid breathing and increased respiratory effort
  • High temperature
  • Recumbency
  • Opisthotonus (also known as star gazing, see photo above)
  • Sudden death

When samples are taken at post-mortem, there is significant damage to the heart and skeletal muscle, and significant pulmonary edema (see photos below).

Animals that survive an initial poisoning can show up later with signs of congestive heart failure: depression, weight loss, rapid breathing, submandibular and brisket edema, and sudden death.

graphic showing damage to heart and lungs with lasalocid toxicity in calves

How does lasalocid poisoning occur?

Toxicity tends to occur in two scenarios:

  1. Mixing errors in the feed mill. This has been the cause in numerous case studies from around the world, with lasalocid included anywhere from 10 to 50 times the desired amount.
  2. Where farms are adding a supplement to calves’ milk feed and, through error, calves are overdosed. This error might be adding extra scoops of a powdered additive or not shaking a liquid supplement.

The normal dose rate of ionophores is 1mg/kg body weight. Signs of toxicity are reported in young calves at just 3 to 5 times that rate, whereas in older animals 10 to 50 times this rate is needed to cause disease. The effects are worse when high rates are fed for a period of time as opposed to a one-off overdose.

Monensin is another ionophore. It is commonly added to the milking herd’s diet to help prevent ruminal acidosis and bloat. Toxicity results in similar signs in adult cattle.

Be aware, and prepare!

There are a lot of products that are marketed to be added to a calf’s milk diet. These products include a variety of ingredients: vitamins, minerals, probiotic bacteria (such as Bacillus, Bifidobacterium, Lactobacillus, Enterococcus and Streptococcus), yeast extracts, enzymes and lasalocid. Milk replacers also regularly contain lasalocid.

It is important to look at everything that calves are being fed and identify which ones contain lasalocid. Ensure that 1) they are being fed as per label instructions and 2) that when fed together toxicity won’t result.

If you have any questions about lasalocid, please call one of our Production Animal veterinarians on 1300 838 700.

As an aside, ionophores are particularly dangerous for horses and dogs: don’t let dogs drink treated calf milk and avoid feeding cattle feed to horses!