Factsheets - Sheep & Beef
The following fact sheets have been prepared by Anexa FVC Veterinarians as a guide to topics of interest. For specific information please contact your local vet.

Fly Strike Control

Fly Strike Control
We are experiencing high levels of fly strike this season and recently the efficacy of Cyrazine came into question when it appeared ‘not to have worked’ on three farms. Merial Ancare carried out an investigation into the situation and the results were very interesting.

Farm One

On this farm Cyrazine had been applied at a ‘double dose’ but animals seemed to still be getting fly strike. The product was being applied with a hand jetting system, and on investigation it was discovered that less than half the recommended volume was being applied and insufficient coverage was also an issue.

Farm Two

On this farm, Cyrazine had been used through a jetter, but despite using a 1.5X dose rate, only 40% of the recommended volume was being applied resulting in only a 60% dose per animal.

Farm Three

These lambs did not have adequate wool growth for the product to adhere adequately.
All farms were affected by the particularly high rainfall in the area during the period e.g. there was 70-100mm rain on the 16th February alone. This causes wet animals and stripping of product.

The Cyromazine molecule does not bind to wool grease like many others, and you really need 24 hours dry to get good contact, and another 6 days for it to be well incorporated into the fleece.

Sheep need six to eight weeks of wool growth for adequate product to adhere. Sheep should only be lightly dagged,if necessary, as adequate wool in the crotch is required for retention of the chemical.

Challenge is particularly high this year, and it is difficult to wait for sufficient wool growth after shearing without cases of flystrike occurring. Remember Clik and Clikzin are licenced for use off-shear, and Clik gives 16 weeks protection. It is more expensive, but the after effects of flystrike are severe. A sheep that has had fly strike will have an 80% reduction in fertility for that year.

Animals with flystrike are best treated with Cyrex, which is a combination product and will give treatment and protection, when applied correctly.

The lessons to be learnt from this investigation are that it is vital to read the label on your product and apply exactly as directed. The other worry is, that it appears many farmers are effectively under-dosing with product; a situation which can rapidly result in resistance. Leading Parasitologists in New Zealand are concerned that the next big issue will be resistance of flies to our current products.

Ensuring product is applied at the correct concentration and in the correct volume, and in accordance with other recommendations is the key to the effective fly control and will aid in minimising the emergence of resistance.

Date Added: Sunday, 2nd April 2017