In this case, a PHD is not an academic qualification to manage all the winter housing challenges, but instead it is a highly practical solution which offers cattle both significant health and production benefits.

In this context, with a PHD we mean a Pre-Housing Dose. This is the treatment of cattle four to five weeks prior to housing with a product which has persistent activity against stomach worm (Ostertagia) and lungworm (Dictyocaulus). It is not an extra dose; it is the dose which is generally given at housing.

Why dose cattle at this time of year?

Cattle will have acquired both a gastrointestinal worm and lungworm burden, along with fluke, during the grazing season.

All parasites have a negative effect on the weanling’s immune system and lungworm in particular can damage the lungs and increase the risk and severity of pneumonia. Lungworm is therefore probably the most significant parasite for Irish cattle being housed in the autumn. Not only do adult lungworm cause irritation and obstruct the airways, the larvae damage the lung tissue while migrating through it before reaching the airways. This causes the lungs to function less efficiently and makes them more susceptible to invasion by both viruses and bacteria at housing. Lungworm larvae and adults are killed and removed quickly after dosing, but it can take two to three weeks for the lung tissue to heal.

This is where the PHD comes in; the first step in successful pneumonia control is to ensure that cattle are housed with a clean set of lungs, free of lungworm larvae.

Would it not be better to treat lungworm infections while the weanlings are still at grass, in a healthy outside environment and to allow healing to occur without the challenges of dust, ammonia, viruses etc?

This does not mean more doses because there are wormers that have a persistent effect against both lungworm and stomach worms, meaning they kill the worms at the time of dosing and for the following five weeks.

Which wormers qualify to be used as PHDs?

Any dose that has a period of persistent activity against both lungworm and stomach worms of five weeks or more. Cydectin Pour-On, Cydectin 1% Injection, Cydectin TriclaMox Pour-On and both Dectomax Injection and Dectomax Pour-On all have at least five weeks' persistent activity against both lungworms and stomach worms from a single dose. As a result, cattle which receive a PHD with a Cydectin or Dectomax product and are dosed within five weeks of housing, do not require another worm dose at housing.

What are the advantages of a Pre-Housing Dose?

1. Cattle are housed with a “clean set of lungs”, are free of lungworm and have recovered from the damage that the worms have caused. This means animals are healthier and better able to fight off the challenges of viral and bacterial pneumonia at housing, resulting in improved welfare, productivity and reduced need to reach out for antibiotics.

2. Cattle will perform better for the last few weeks at grass in the autumn due to persistent control of stomach worm. As a result, they will have improved appetites and feed conversion efficiencies, leading to better daily liveweight gains and a smoother transition to housing and the winter diet.

3. Cattle can be vaccinated against viral pneumonia at the same time as receiving their PHD, allowing the full onset of immunity to develop against the viral challenge they will experience as soon as they are housed.

4. Lice control. If a pour-on product is used, it will kill off both the adult lice and the nymphs/larvae when they hatch from the eggs in the next five weeks, resulting in lice-free cattle entering the sheds. These sheds will be free of lice, as they have been empty all summer, so no further lice treatments will be required this winter.

The dose given to cattle at the end of the season is likely to have the biggest impact on their welfare and productivity. We must therefore ensure not to compromise on the housing treatment and get the most from the autumn dosing programme by giving cattle a PHD using either Cydectin or Dectomax products.

All Cydectin® products contain moxidectin. All Dectomax® products contain doramectin. Legal category LM.

For further information please check the SPC or contact Zoetis (01) 2569800. Use medicines responsibly. ZT/21/24/1