Farm Ireland

Sunday 17 December 2017

Control the parasites in your flock

Michael Gottstein
Michael Gottstein

Michael Gottstein

In last week's article I outlined some of the nutritional aspects that affect lamb performance. Supplying sheep with adequate nutrients is key to achieving high levels of animal performance. But what if the sheep are unable to digest these nutrients? That's what happens when the sheep are carrying heavy parasite burdens.

Once lambs start eating grass (around five weeks of age) they will start to come in contact with various parasites. These parasites live off the nutrients/ tissue in the lamb's digestive tract thereby reducing the amount of nutrients available to the lamb and in some cases causing damage to the digestive system of the lamb.

Understanding which parasites cause the damage and how to control them is essential if lamb performance is to be optimised in the coming weeks.

Many of this year's lamb crop will come in contact with two parasites that can cause severe illness and in some cases can even lead to the death of young lambs. The parasites that I am talking about are nematodirus and coccidiosis.

The symptoms of both parasites are very similar and in some cases the lambs can receive a double whammy and be affected by both at the same time. Therefore, understanding the lifecycle of these two parasites is key to controlling them within the flock.

First, let's look at nematodirus. This is an infective larvae that has a very unusual lifecycle insofar as the infection that lambs will pick up this year is as a result of eggs that were passed out onto pasture in 2008/2009 by other lambs or calves. The reason for this is that the eggs that are passed onto pasture will not hatch until they undergo cold spells below 0°C.

Once this requirement has been met the larvae will hatch after a warm period (ie, 24-hour period of temperatures above 10°C). Because of the conditions required for the larvae to hatch, many of the eggs that were deposited on pasture in the past two years will all hatch at the same time, resulting in a mass problem. If large quantities of these larvae are ingested by lambs, they will cause damage to the lamb's digestive system and the lambs will start to scour. The recent milder weather is likely to have met the requirements for a hatch in certain parts of the country, so be vigilant and treat lambs at the first sign of disease. Nematodirus infections can be controlled by dosing, providing the lambs with 'safe' pasture (ie, fields that did not have calves or lambs on them in the past two years) or a combination of the two. Older sheep are generally immune to nematodirus and therefore do not require treatment.

When treating lambs that have been affected by nematodirus all anthelmintics groups are effective, but it is important to get in and treat the lambs early, before the gut has been too badly damaged. Where excessive damage has been caused to the gut, future lamb-thrive will be compromised.

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The second parasite that causes problems in young lambs, and is often mistaken as nematodirus, is coccidiosis.

Coccidiosis is characterised by a dark or sometimes bloodstained scour. Even more so than is the case with nematodirus, lambs will rapidly develop irreparable damage to the digestive tract and mortality can be high where treatment is delayed.

Coccidiosis also over-winters on ground that was grazed by sheep in the previous year. Therefore, if coccidiosis was a problem last year it is likely that where sheep graze the same ground, it may become an issue again this year. Where 'safe' pasture is provided the level of infection can be greatly reduced. Hygiene is also a major tool in reducing or preventing coccidiosis infection in young lambs.

The parasite needs wet conditions to multiply and survive. Consequently, moving feeders regularly, avoiding leaking water troughs and keeping sheep well bedded (indoor systems) can all help to reduce the parasite burden.

Newborn lambs will have maternal immunity against coccidia but this usually wanes after three to four weeks, or during periods of stress. Immunity is regained at around eight to 10 weeks of age so there is generally only a short period in between when control may be required.

Where lambs become infected during the susceptible period, they will shed millions of oocysts (eggs) onto pasture. If those paddocks are subsequently grazed by later-born lambs at a time when they are susceptible to infection, the infection from previous grazing can lead to extremely high parasite burdens.

So how do we identify what parasite is causing the problem? In practice this can be difficult.

Faecal egg counts are not useful tools to identify parasite burdens in both cases. Therefore, the best advice is to treat for nematodirus and if the lambs are still scouring you should go in and treat for coccidiosis.

Coccidiosis can be treated by oral dose (vecoxan/Baycox), sulpha drugs or in feed medication if the lambs are consuming creep feed.

Irish Independent