As we move into worm season, have a think (if you haven’t already!) about how you’re going to monitor worm status on your farm this year. There are three main ways to do this:
- Faecal Egg Count (see below for how to do this) – FEC provides a measure of the contamination of a pasture with worm
eggs at the time of sampling, and hence an estimate of the magnitude of parasite challenge and likely risk of disease over the next few weeks. It’s good for monitoring the worm status of groups over time, e.g. when done three-weekly on permanent pastures, but there’s no consistent relationship between the FEC and the number of worms in an individual animal, the amount of damage done to the gut, or the performance of that animal. FECs are therefore better used as a tool for monitoring groups and deciding when to worm them than for diagnosing worms in individual animals. They are also used in FEC Reduction Tests, which measure FEC at set intervals before and after worming to determine how effective a particular wormer is, and whether there are any signs of resistance.
- Daily Live Weight Gain – As long as nutrition is adequate, DLWG is a good indicator for subclinical worm infections in calves or lambs at pasture (i.e. worm burdens that reduce food intake and performance but without being so severe as to cause diarrhoea or obvious ill-thrift). Using scales or weigh tapes every two or three weeks, and comparing growth rates to targets, can be a very accurate and simple way of monitoring worm burdens. Treatments should be given when DLWG drops below target.
- Plasma Pepsinogen – This involves blood testing animals for pepsinogen, a marker for abomasal damage caused by O. ostertagi, one of the major gut worms in cattle and sheep. It’s useful to monitor worm damage both in groups, when about 6-10 animals should be tested, and for individuals, for example to see if scour and weight loss is due to worms or not. It’s reliable but reasonably expensive, and the blood results can take a while to come back from the lab. It’s perhaps more useful in cattle as a pre-housing test to see what level of worm damage a group has encountered during the grazing season.
Guidelines For Faecal Egg Count Sampling From A Group
- Collect samples from at least 10 animals. Sample at random – don’t pick and choose which animals.
- Samples must be fresh when collected – ideally less than an hour old, definitely less than 12 hours old. If faeces are too old, some eggs will have hatched, making the FEC seem lower than it actually is.
- If collecting from faecal pats rather than directly from the back end, take a small amount of muck from three different areas of the pat, since eggs may not be evenly distributed.
- Put each sample into an individual airtight container – ideally small screw-top pots, such as milk sample pots (you can get these from us if necessary). Don’t mix the samples together – we’ll do this in the lab using scales, to make sure we get exactly equal amounts from each.
- Fill each pot, to exclude as much air as possible. Please don’t use plastic bags or gloves as containers – our lab staff have to handle a lot of samples and small pots are far better!
- Deliver to the lab within 48 hours, sooner if possible.
- Before delivery, keep samples cool – refrigerate if possible, but don’t freeze.
- Don’t forget to label all the pots with the farm name, the date and, if you’re sampling different groups of animals, the group’s name or number.
Worm risk varies year to year and region to region. Keep up to date with what’s happening in the local area with Zoetis’ Parasite Watch scheme, which works with monitor farms across the UK (www.parasitewatch.co.uk). And as always, give us a ring with any questions!