Goat Drenching Information

Sustainable worm management

Managing worms in goats is one of the most challenging aspects in providing preventative care for the animal. Goats are more susceptible to parasitism than sheep and cattle and drench resistance on goat farms is widespread. “Business as usual” is no longer an option as reliance on chemical drenches is a worm control practice that is not sustainable. What you do to manage worms will have a huge impact on maintaining the sustainability of effective drenches for longer.

Intestinal parasites can result in chronic weight loss. Worms cause damage to the gut lining leading to inefficient feed utilisation and scouring. Worms feed off the gut lining “robbing” the animal of nutrients and some worm types suck blood which can lead to death from blood loss. High worm burdens cause appetite suppression and increased demand on the immune system.

Age and immunity

Younger animals provide a fertile breeding ground for multiplying worm populations and are the major source of pasture contamination.

In goats, full immunity to worms often doesn’t develop, even once they reach adulthood. Many goats remain susceptible throughout their life, especially when the immune system becomes depressed through stressful events such as kidding, lactation, shearing and feed shortages. Goats will not always show signs of scouring and some goats can accumulate large burdens of worms without obvious clinical signs until the load becomes very severe and they “crash”. These cases can be difficult to turn around.

Successful worm management therefore involves an integrated approach that considers grazing, animal and drench management strategies.

Seasonal pattern of larvae on pasture

The danger periods are from spring to early winter with peak larval numbers occurring in autumn. Warmer, wet conditions allow worms to complete their lifecycle faster with fewer eggs developing over the winter months due to colder conditions.

The number of eggs and larvae on pasture is much higher than the number of worms inside animals. Drenching will remove the adult and immature worms that are present within the gut today, it cannot prevent the ongoing ingestion of larvae from pasture. Therefore, trying to completely eliminate worms is counterproductive as animals require constant exposure to low worm challenge to maintain some level of immunity. A better approach is to feed goats well and accept there will be some worm challenges that require management.

The lifecycle of common intestinal parasites

There are several different types of intestinal worms that infect goats. The most important ones are roundworms with three phases in its lifecycle: egg, larva and adult. The adult stage lives in the stomach or intestines and when mature sheds eggs which pass out in the dung. An immature worm hatches out of the egg in the dung pat and then progresses through four larval stages. Some of these occur within the dung, whereas the third larval stage (L3) is the infective stage which can migrate out of the dung onto soil and grass where it can be eaten by a grazing animal.

The development of worms from egg through larval stages to maturity requires a moist environment and warm temperatures and typically takes 21-28 days to complete in ideal conditions. At low temperatures, development is slow, wheras development is much faster in warmer temperatures. 20-25oC is optimal to rapidly complete the lifecycle.

MANAGEMENT OPTIONS

GRAZING MANAGEMENT

• When goats are well-fed year-round and under minimal stress, a better functioning immune system can tolerate parasite challenge without the need for drenching.

• Monitor pasture length. Most larvae are in the bottom 2cm of pasture and grazing low increases intake of larvae. Goats prefer to eat long pasture and do best if pasture height is around 11cm in winter and 7cm in summer.

• By nature, goats are ‘browsers’, so offering a diet of pasture, seed head, shrubs and trees (e.g. willow) will reduce larval challenge. Offer supplements off the ground. o Reduce overstocking. The higher the stocking rate, the higher the potential worm burden.

• Cross grazing with other species (e.g., goats followed by cattle). Goats share the same worm species as sheep so avoid grazing goats in the same area with sheep, but sheep are still better than more goats! It will take several months of grazing by cattle to effectively reduce the level of goat worms on pasture (>6+ months).

• Larvae can survive for many months, even years in the right conditions. Cold weather only slows development and does not kill some worm species. Spelling pasture will reduce the level of contamination but under NZ conditions spelling for 12-24 months may be necessary to have any significant reduction in larval loads.

• Aim to reduce the number of larvae consumed in the first place. Drenches will only remove the adult worms and larvae from the gut while the drench is active. They don’t prevent the ongoing ingestion of infective larvae which remain on pasture. Provide objects for goats to climb on to keep them off pasture.

• Prepare a clean paddock/area for use over stressful events such as kidding, but don’t drench and immediately move onto clean pasture. Avoid grazing kids in autumn paddocks where does will kid the following spring.

• Goats may be housed and fed in a barn and held off-pasture to allow grass to regrow to acceptable pre-grazing lengths.

ANIMAL MANAGEMENT

• Consider strategic drenching of young goats under 12-18 months of age. For the first couple of months of life, kids don’t require drenching as a high proportion of their diet is milk. For kids, a preventative drench strategy should consist of 4-5 drenches given at 28 day intervals starting at weaning and over the summer-autumn period to 12months of age. For smaller numbers of kids, one at weaning and one or two on an as-needed basis may be all that is required.

• Maintain refugia. “Refugia” refers to part of the worm population that is able to reproduce without having been ‘screened’ as drench survivors – they are taking ‘refuge’ from the drench. Undrenched animals contribute susceptible worms to refugia.

• Don’t drench and shift animals. Drenched animals should ideally be held off-pasture for at least 24 hours after drenching so any resistant worm eggs can be contained.

• Leave a proportion of animals un-drenched. Recommend 5-10% of heavier, well-conditioned animals to provide a refugia of susceptible worms. The main exception is late summer/early autumn when Barber’s Pole is most active or if there is a high degree of pasture contamination.

• Quarantine introduced animals for 2-3 days and drench with at least 4 actives. This will require 2 drenches, twice at 24hour intervals (4 drench doses total). Then graze new goats in an area likely to be contaminated with existing goat worms to dilute out any multi-drench resistant survivors. DO NOT move them onto “clean” pasture – this will ensure a strong selection pressure for resistant genes. A drench check is advised using a FEC 7-10 days after quarantine drenching.

• Increase FEC monitoring around stressful events such as kidding, shearing, low pasture height.

• Be prepared to offer supplements when pasture gets short (hay, nuts, grain, vegetable scraps, branches) to maintain body condition and avoid grazing too low

DRENCHING MANAGEMENT

• Regular drenching of adult goats is unnecessary - only drench on an as-needed basis. Always use individual FEC’s to guide when a drench is necessary as there is wide variation between individual animals in their ability to handle worm challenges.

• A triple combination drench should be useful in most situations. Oral drenches are absorbed much better than pour-ons and injections.

• Accurately determine the weight of goats to prevent underdosing (high risk of developing resistance) and overdosing (risk of toxicity).

• Dose goats to 1.5 times a labelled sheep dose rate since goats metabolise drugs faster than sheep.

• Hold goats off pasture (but they must have access to water) for 24 hours prior to drenching and 12hr after (not advisable for does with kids). Repeat the dose 24hours after the first dose to increase effectiveness. Remaining off pasture for the 24hr between drenches and 12hr after the second drench is sufficient if combining strategies.

• Administer the drench nozzle over the back of the tongue. Swallowing can trigger rumen bypass and reduce potency of the drench – the drench needs to end up in the rumen for it to be absorbed properly.

• Monitor drench efficacy (post-drench FEC) 1-2 times a season.

• Avoid using long-acting products. These add considerable selection pressure for the development of resistance.

• Drenches should not be given at intervals of less than 28 days.

• DO NOT rely on repeated use of novel drenches (Zolvix Plus). Resistance will quickly develop. This drench should be reserved for use under veterinary instruction only.