This project aims to explore the potential benefits of multi-species grazing of sheep with ducks in order to address the parasite Parelaphostrongylus tenuis (P. tenuis, a.k.a brain worm/deer worm). This parasite is transmitted to sheep through deer and then slugs/snails before affecting sheep. Infection often leads to paralysis and death of the affected sheep. In the past, we’ve demonstrated that ducks can reduce slug populations that are a pest to shiitake mushroom production (Project FNE12-745)
Due to the historic D3 drought in our region this season, we opted to delay the start of monitoring slug populations to the 2017 and 2018 seasons. Our past experience meant we knew the work would produce less than valuable results, because slug populations are virtually non-existent during dry times. Additionally, the drought conditions meant that pasture did not grow after the sheep’s first rotation in May.
We spent 2016 reorganizing our grazing system to accommodate drought and make use of hedgerows, which will help tremendously as we set out to collect data over the next two seasons. We did lose one sheep to the P. Tenuis parasite in 2016, a previous infection from 2015 that was not treatable. No new sheep were infected, possibly because of the extreme drought and thus poor parasite conditions. Because of new job responsibilities, the original project leader Elizabeth has brought in co-owner and husband Steve Gabriel be responsible for all aspects of implementing, monitoring, and reporting for the project.
Wellspring Forest Farm is a 10-acre agroforestry and permaculture inspired farm and homestead. The farm is coowned and operated by Elizabeth and Steve Gabriel and we’ve been growing crops since 2011. We also graze our neighbors 20 acres of pasture. Our gross income was $11,063 in 2014. We develop our operations systematically, analyzing resources and challenges of the site, our economic capacity, time, personal interest and market demands.
Our main crop is shitake mushrooms, which we sell to restaurants and through a CSA. We maintain a flock of 50 ducks that provide slug control to the shiitakes and nitrogen to our gardens. We sell eggs to a butcher and restaurant. Since 2012, we have planted trees to eventually provide wind protection, fodder, shade and wood.
Sheep complemented the operation because our pasture is in need of regeneration and sheep are much more sustainable than mowing between the rows of tree crops. We expect to have around 28 sheep in 2016 and have a goal of managing about 20 ewes and 30 lambs each year from 2018 onward. Adding ducks to the sheep rotation, we hope further improve soil health, reduce sheep exposure to parasites and increase farm production.
This project builds off our previous research (FNE12-745) where we determined best practices for utilizing ducks to control slugs in our log-grown shiitake enterprise. We are mostly interested in having ducks on the farm for this pest control benefit, but have also found a modest income from egg sales. Our success with ducks in the mushroom enterprise and anecdotally in our gardens and orchard systems has led us to see their benefit to many systems. Moving them into the sheep rotation may be beneficial, but there is likely an issue with getting the proper timing down to have efficacy. Our main question; is it worth rotating the ducks in sheep paddocks to reduce the slug population and thereby reducing our sheep flock’s exposure to parasites?
Big thanks to Jonathan, Shaun, and Claire, our on-farm help in 2017 who were awesome and stayed positive even while counting slugs!
Our goals for the project are to:
Objective 1: Determine if grazing 50 ducks reduces gastropod populations in paddocks ~12,000 square feet
Objective 2: Reduce brain worm parasite risk to grazing ruminants, thereby reducing the need for Ivomec, dexamethasone, and Safeguard
Objective 3: Determine ideal timing of leader-follower rotation that results in low gastropod population, minimal duck poop presence on pasture, and diverse and abundant forage
Due to the historic D3 drought in our region this 2016 grazing season, we opted to delay the start of monitoring slug populations to the 2017 and 2018 seasons. Our past experience meant we knew the work would produce less than valuable results, because slug populations are virtually non-existent during dry times. Additionally, the drought conditions meant that pasture did not grow after the sheep’s first rotation in May. We spent 2016 reorganizing our grazing system to accommodate drought and make use of hedgerows, which will help tremendously as we set out to collect data over the next two seasons.
We realized as we planned for the 2017 season that starting to rotate ducks into paddocks would not be useful without first establishing baseline data for each paddock, since it cannot be assumed that slug populations are the same for each location, nor do they stay consistent with the seasonal changes in weather patterns.
If we stated integrating ducks right away, we might observe differences in control vs. treatment paddocks that we would attribute to duck activity, when the variability may in fact be due to other factors. The main factors we believe affect the presence of slugs in paddocks include 1) recent weather, especially precipitation, 2) length of the grass, 3) previous impacts on slug populations
Therefore, we decided that in 2017 we would collect slug population data and track our sheep grazing, as we might normally do. We could then look and see if there are any trends in slug populations, any differences among paddocks, and any correlation with weather events.
In order to monitor slug populations in 2017, we distributed traps made from soda bottles (see figure 1.1) in 10 locations in each paddock, roughly 50 feet apart. Each trap was sunk into the ground using a bulb digging tool and set so that the opening of the trap sits at ground level. We filled the trap with about 1 – 2″ of fresh beer. The map (see figure 1.2) of these trap shows we aimed for a relatively even distribution of traps, though there is some variability in the shape of the paddock. We selected the paddocks in the wettest locations closest to the woods edge, as we assume these are more likely to have slugs (intermediate host) and also deer visiting the pasture, who are the origin host for the parasite in question.
We planned to monitor traps twice each week, counting slugs captured and also emptying and refilling with fresh beer, an important practice to ensure the traps would continue to attract slugs. A basic count of the total slugs was taken per paddock and recorded. We tracked these figures from June 19 through October 13 a total of about 17 weeks of study.
As the graph below shows for the year 2017, results of the data collected indicate there will be some consistency to the pattern of slug presence among the collection of paddocks selected for this study. This is useful as we attempt to add ducks to 3 of the paddocks in 2018, to see if we can affect populations. If successful, those paddocks would hopefully deviate from the overall trends.
When comparing this graph to local precipitation data for the same timeframe, there is not a clear correlation between anything happening with precipitation and a “response” from slug populations:
We are ready to proceed to the treatment portion of the research in 2018, and will better track grazing in the paddocks, as well as grass height, as we are curious if this has any effect on slug presence. We will accomplish this by measuring the average height as we take slug counts. Our theory is that less grass = more drying out, which could have an effect.