Liver fluke is a major cause of ill-thrift and premature death on sheep farms. According to the Regional Veterinary Labs, more than 20pc of adult sheep submitted for analysis in 2008 had succumbed to either acute or chronic liver fluke.
One issue that I frequently come across when talking to sheep farmers about this disease is that they will have dosed the sheep but may still be suffering ill-thrift or deaths because the product used was inappropriate for the type of fluke present, or the product was no longer working on the parasite population on that particular farm.
When treating sheep for fluke it is essential that you make sure the product you use is effective for the age and type of parasite being targeted. Trade names are deceptive, as there are lots of flukicides that contain the same active ingredient but are sold under different brand or trade names. It is important to look at the active ingredient and see what type of fluke it is effective against.
I frequently come across farmers that have had reports back from the abattoir about immature fluke in livers and then dose using a member of the oxyclozanide/albendazole group because they have short withdrawal periods. The problem here is that this group of flukicides is only effective against adult fluke and therefore not suitable for use in lambs that are actively picking up fluke infections and suffering from acute fluke disease.
There are five different 'families' of flukicides. Get to know them and, when buying a product, check the active ingredient and do not buy them based on the brand or trade name. The table (below) contains the various flukicide families and shows at what stage of fluke they are effective.
Parasitic worms present a major challenge for both sheep and sheep farmers. Again, similarly to what has already been mentioned regarding flukicides, it is important to use the correct wormer.
Teagasc surveys have shown that there is widespread resistance to both benzimidazole- and levamisole-based worm drenches on Irish sheep farms. Therefore, the first port of call when planning a parasite- control programme should be to find out if the drug is still working on your farm.
Every year I receive calls from farmers who have gone to the expense and trouble of drenching their lambs only to find out a few weeks later that the lambs are not thriving and the labour involved in treating the sheep has also been lost.
At present, Irish sheep farmers only have three families of anthelmintics (worm drenches) available to them. These are benzimidazole (white drench), levamisole (yellow drench) and macrocyclic lactones (avermectin/moxydectins). Again, understanding which active ingredients should be used is far more important than focusing on brand or trade names.
In spring (up to May) the main parasite from a worming perspective will be nematodirus.
All three family groups are effective against this parasite and, to date, there has been no evidence of nematodirus resistance to any of these products.
After May the focus turns to other stomach worms and this is where resistance issues come into play. Regardless of what product is being used, its efficacy should be checked every two to three years by doing a post-drench faecal egg count reduction test. If the results of this test show that the product is not working then it should no longer be used to control stomach worms.
Mastitis in sheep post-lambing is a major concern. Mastitis occurs when an infection enters and develops in the udder. In mild cases the affected quarter may be lost and, in extreme cases, the ewe herself may die.
Hygiene around and after lambing is critical in reducing the incidence and spread of mastitis. Indoors, plenty of straw and frequent applications of cubicle lime will help to reduce the level of infection in the environment.
Issues such as orf can also have a big impact on the levels of mastitis experienced in the flock. Lambs that are affected with orf can spread this to ewes, resulting in sore teats and subsequent infections.
Another issue to watch out for this year will be the level of nutrition available to the ewe after lambing. The continued cold weather has resulted in little or no grass being present on sheep farms. Post-lambing ewes need to be adequately fed so they can feed their lambs.
Failure to achieve this can result in the lambs damaging the teats by continually trying to feed. Ewes with sore teats will not allow the lambs to suckle, resulting in the udder not being stripped out regularly and an increased risk of mastitis.
Where a problem with mastitis exists in the flock, talk to your vet about finding out the potential causes and putting in place a plan to eliminate them.
Milk fever (hypocalcaemia) is caused by a lack of calcium in the ewe's diet or her inability to mobilise her own calcium reserves.
Unlike cattle, milk fever is most often seen in sheep before lambing. Affected sheep are dull, refuse to eat and display symptoms that are almost identical to twin-lamb disease.
Affected animals should be treated with a suitable calcium gluconate injection (injected under the skin), which should be warmed to body temperature before being administered.
This disease can be differentiated from twin-lamb disease by the ewe's response to the calcium therapy.
Pregnancy toxaemia (twin-lamb disease) is a metabolic disorder that occurs when the ewe's nutritional needs are not being met in late pregnancy.
Where a significant number of otherwise healthy sheep are going down, it is a sure sign that feeding levels are inadequate.
Affected ewes appear dull or lethargic and may suffer spasms and tremors, or appear blind. Rapid treatment with a glucose/glycerol-based drench is required if the ewe and her unborn lambs are to be saved.
Ewes that are heavily in lamb (triplets and quads) and those that are lame and slow to feed are prone, and should be penned so they have ample opportunity to eat their allowance of concentrate feed.
Hypomagnesaemia (grass tetany) is a lack of magnesium in the blood supply of lactating animals. Poor weather conditions, grass scarcities and stress can trigger the condition.
The uptake of magnesium by the animal is significantly reduced when it is stressed. Affected sheep will rapidly enter a coma and die if they are not treated with magnesium (ideally, intravenously by your vet). Applying a magnesium solution, at body temperature, under the skin may be effective where the affected animal is detected early.
Putting in place measures that prevent the sheep from going down with grass tetany is the best option. In order for this to happen, magnesium needs to be supplemented on a daily basis during risk periods. The reason for this is that magnesium is not stored in the body for long.
The target level of magnesium supplementation is 3-5g of magnesium/hd/day. Protection will occur one to two days after supplementation starts and will last for one to three days after supplementation ceases.
From a practical point of view the main supplementation methods for sheep farmers are:
- Hi-mag bullets;
- Mineral licks;
- Meal containing Cal-mag;
- Pasture dusting.
Water medication, which is often used with dairy or suckler cows, is not successful with sheep. It is important to limit the access of male animals to magnesium if urinary calculi is to be avoided. There is no safe amount of magnesium that can be fed to male sheep.
What sheep farmer doesn't have lame sheep? Controlling lameness is a huge but necessary cost on sheep farms. In flocks where lameness is kept at very low levels (less than 5pc), the costs associated with keeping it at these low levels can be more than €1/ewe/year -- even more where sheep are vaccinated against footrot.
This is, however, only a fraction of the cost of lost performance where lameness within the flock is not kept at low levels.
Travelling to sheep farms, I find the incidence of lameness is closely linked to the footbathing facilities available. Farms with poor or non-existent footbathing facilities will often have much bigger problems when it comes to lameness.
For a footbath to be effective, the solution needs to be the correct concentration and the sheep's feet need to remain in contact with the solution long enough for it to be able to work.
The appropriate footbathing solution strengths are given in the table (below).
Ideally, the footbath should be a stand-in type where several sheep may be left standing in the solution for longer periods of time, say 10 minutes.
Where this type of footbath is not an option then the next best is a walk-through footbath that is at least 4.5m long, but ideally 6m.
The key to reducing lameness in the flock is to footbath the sheep on a frequent basis -- ideally before they are lame. Remember that lame sheep will not immerse the affected feet in the footbath solution. Therefore, preventative footbathing is the way to go.
Another point that is often overlooked is that the sheep should also be footbathed during the housing period and not just at housing and turnout.