Most adult sheep have low worm egg counts in early summer and a drench at that time is not warranted; delaying a drench until late March or April allows some less-resistant worms to survive.
Lambs should be treated beginning at around six weeks of age. Mature ewes are more tolerant to high worm loads than are lambs. Not grazing lambs will significantly reduce the intensity of the deworming program for the ewe flock. When introducing new sheep to the flock, deworm with the most effective product available.
Ewes should only be wormed once a year at lambing time; this will reduce the number of eggs on the pasture so that there are less for lambs to pick up. Lambs have little resistance to worms in their first grazing season but this develops with time.
It's important to note that many wormers are not effective at treating the hypobiotic stages of the larvae so worming during the winter may not help reduce the problem. Climate change is altering the epidemiology of some worm species too.
Efficacy is usually better with moxidectin (Cydectin). Levamisole (Prohibit, Leva-Med) is usually the most effective dewormer. Resistance varies by farm. Due to drug resistance, it is now recommended that clinically parasitized animals be given combination treatments.
For best results in treating parasites, and to protect against potential resistance, sheep should be drenched between once and twice a year, depending on whether they are breeding or not. Based on the Australian climate, the first drench should be conducted in the summer season, usually around November or December.
Adult ewes have a natural immunity to worms and therefore should not be wormed repeatedly, once per year around lambing time should be all that is needed (if that). Worm egg counts can be used to determine whether lambs need worming through the summer for parasite gastroenteritis (Ostertagia).
IVERMECTIN DRENCH-Sheep and goats receive the same treatment. Use Ivermectin drench at twice the label dose, (20cc Per 100lbs-Orally). Fast for 12-24 hours prior to use. Ivermectin is safe for all classes of animals.
Using this knowledge to control worms
In very hot districts, a further month can be taken off; extreme temperatures over 40°C for a couple of weeks will kill most larvae. More information on preparing low worm-risk paddocks can be found here: Grazing management.
Most adult sheep have low worm egg counts in early summer and a drench at that time is not warranted; delaying a drench until late March or April allows some less-resistant worms to survive.
Garlic – Use garlic as a worm-preventative and effective dewormer treatment. It aids in digestion and decreases worm counts. You can also mix garlic with molasses; try feeding it to them right out of your hand.
The most important vaccines given routinely to sheep and lambs in North America are those used to protect against Clostridial diseases. Specifically, the preferred vaccine is CD-T toxoid. This protects against enterotoxemia caused by Clostridium perfringens types C and D and also tetanus caused by Clostridium tetani.
Sheep and goats can and will be affected by worms in winter
These infective larvae will be ingested by sheep and goats grazing the affected pastures during winter. Depending on the contamination levels, it is quite possible for the stock to acquire large worm burdens in winter resulting in illness and death.
However, to avoid unwanted effects (although rare) such as abdominal pain, nausea, etc., users should drink it after breakfast. But if you want the drug to have the best effect of killing worms, it should be taken 2 hours after dinner or early in the morning on an empty stomach.
Dry conditions force parasites to stay at the base of the plants where they are less likely to be consumed by the livestock. Sheep (and goats) are generally not affected by the same internal parasites as cattle and horses.
Overdosing sheep or lambs with drench or incorrect pre or post drenching management can be fatal so it is important to consider how you drench as well as 'when' and 'what with'. Key drenching principles include: Always read the product label for both dosage and safety information.
Some of the products that may interact with this drug include: barbiturates (such as phenobarbital, butalbital), benzodiazepines (such as clonazepam, lorazepam), sodium oxybate (GHB), valproic acid.
Closantel kills virtually all haemonchus larvae for at least four weeks after drenching and moxidectin (Cydectin®, Moximax®, Moxitak®, Sheepguard®, Topdec®) for at least two weeks. Moxidectin is also available in a long acting form that will give protection for 91 days (Cydectin LA ®, Mxaximus®).
Some dewormers, like Cydectin, can be found in different formulations (injectable or pour-on) for different species. However, only formulations labeled for sheep should be used in goats or sheep.
The most common internal parasites in sheep and goats are: lung worms (Dictyocaulus spp. or Muellerius capillaris); stomach worms (Haemonchus contortus, commonly called barber pole worm); liver flukes (Fasciola hepatica); and intestinal parasites, the most common of which are coccidia (Eimeria or Isospora).
Once larvae have left the manure and are exposed on the pasture, sheep consume the larvae along with the pasture and become infected with worms. Worms can live in the sheep's gut for many months. Some species can live exposed on the ground for six months or longer in favourable conditions.
Tapeworm segments can be seen in the feces of sheep and goats. They have a white, grain-like appearance. Adult worms, often up to a meter or more in length, can be expelled and passed in the environment. Tapeworm eggs can be seen in sheep and goat feces, using the standard worm count procedure.
The most common clostridial diseases that affect sheep are tetanus, blackleg, malignant oedema (blood poisoning), and pulpy kidney (which affects lambs).
In other words, the parasite larva reach the infective stage after the sheep or goats have moved out of that field. Larva can survive for long periods, even as long as 120 days, when weather conditions are cool and moist. However, when the weather is hot and dry, those parasites can die very quickly.