Final report for FNE20-954
The purpose of this project was to study controlling larval development of pests and parasites biologically using black soldier flies. Briefly, black soldier flies were reared in a sheet metal barn and a white firm high tunnel barn on used, fecal containing, sheep bedding materials. A sample of the black soldier fly composted bedding material was then taken for analysis for fertilizer value, and the remainder spread onto a clean pasture. Two additional paddocks were also set up with no additional material added to clean pasture (negative control), and non-composted sheep manure and bedding material added to another clean pasture (positive control). Fecal samples were collected from 18 lambs which were randomly divided into the three pastures. These samples, and a second set of samples collected after four weeks on pasture were sent for fecal egg count analysis. Lastly, fly strips were hung weekly in each of the two barns where the black soldier flies were raised as well as cooperating farms with a comparable number of sheep to compare effectiveness of the black soldier flies in reducing pest flies.
The results did not support advising farmers to adapt this practice as conducted in this study. The portion of the study designed to evaluate the effect against parasites needs to be studied further as the positive control was ineffective. Fertilizer value was only slightly altered and barn type was not the most significant factor in determining the ability of the black soldier fly larvae to utilize the sheep manure and bedding material. The presence of the black soldier flies was unable in this unusually cold Spring to outcompete pest flies and the black solider fly larvae may have contributed to encouraging pest birds to nest in the barns. It may be possible for this practice to be implemented in warmer climates or with modification to the black soldier fly rearing process.
The questions are:
- Can black soldier flies compost sheep manure and bedding material under two barn conditions (dark sheet metal/white film high tunnel) in Maryland?
- Will the fly population in lambing barns with active black soldier fly composting bins be comparable to lambing barns utilizing alternative fly management control?
- Will the compost volume be reduced and how will the nutrient value compare to non-composted sheep manure and used bedding?
- When lambs graze on a clean pasture to which black soldier fly compost has been applied, will they have a higher fecal egg count than prior to grazing, and will it differ from lambs grazing on clean pasture to which no compost was applied. How will the egg counts compare to lambs grazing on pasture to which non-composted sheep manure and bedding is applied?
If the project is successful, this model may be adapted by other farms. For fly prevention, this study may demonstrate fly control equivalent to other measures. Finding an effective way of treating parasite egg contained in manure and bedding will provide farmers a safe way of utilizing this material. Organic farmers and conventional farmers will likely welcome a non-chemical alternative to both of these serious threats to sheep.
Sheep bedding and manure can accumulate over the winter in barns and run-in shelters for sheep. Sheep manure and used bedding are used by pests such as house flies and blowflies and parasites for larval development. House flies, are important pests in livestock production systems carrying disease transmitting organisms that affect humans and animals. Of all domestic animals, sheep are the most susceptible to flystrike, because of their wool, particularly dirty wool attracts blowflies (Sheep 201). Sheep bedding is often contaminated with parasite eggs as ewes shed higher levels of eggs around parturition and through most of lactation. Parasites are able to protect themselves by remaining in manure pack when environmental conditions are not suited to their development and resume development and infection once conditions are favorable (OSU, Understanding Parasites). This nutrient dense and moist environment serves as a breeding ground for flies once the temperature warms. Spreading bedding onto pasture distributes the parasite eggs where they may be consumed by and infect lambs.
Flies are typically a nuisance, but in certain situations can pose significant harm to, and even cause death in, sheep. Flystrike occurs when blowflies lay their eggs around the edges of wounds or in manure-soiled wool. The eggs hatch in 6-12 hours and feed on healthy flesh. If they enlarge the wound or area large enough, it can be fatal, but if caught early enough the animal can be treated with hydrogen peroxide or avermectin. Nose bots Oestrus ovis at either the mature fly or larvae stage cause irritation as the grubs crawl through the nostrils and sinuses. The inflammation and secretions can cause a lack of appetite, and stress of being annoyed by the flies can reduce grazing. Pink eye is typically transmitted by direct contact, but flies may also carry Chlamydia psittaci (ovis) and Mycoplasma conjunctivae, or predispose or exacerbate the problem. While not typically fatal, treatment is usually required and temporary or permanent blindness can occur depending on the severity of the infection.
The proposed solution in this study is the introduction of black solider flies, Hermetia illucens (BSF), into the sheep animal housing area. Unlike other fly species, neither the adult nor larvae are considered pests or vectors of disease. Instead, they are considered beneficial insects commonly occurring in decomposing organic waste including animal manure. BSF have been found to reduce swine manure bulk by half, producing a low-nutrient, low-odor, dry residue. (Watson) A BSF manure management system for laying hens reduced manure accumulation by at least 50% and eliminated house fly breeding.(Lin) In dairy manure, BSF significantly reduced Escherichia coli.(Liu) At present no studies were found evaluating BSF larvae’s ability to utilize sheep manure or bedding.
The proposed fly control solution is to establish a BSF population so when the barn conditions and temperatures permit, the BSF will outcompete other pests for their food source and reduce the pest population. Females lay approximately 500 eggs at a time, allowing for a rapid increase in numbers under the ideal conditions. BSF larvae are known for a voracious appetite, including consuming larvae of other species. In theory, this should extend to eggs of parasites. The reduced pH of the BSF compost may also help destroy remaining parasite eggs. In addition, since they prevent houseflies and other insects from laying eggs in the material inhabited by BSF larvae, the compost spread onto pasture should not serve as a breeding site for pest flies.
Compost has value as fertilizer for pastures. In order to better understand the impact of using BSF to compost sheep manure and bedding this study will evaluate the reduction in compost volume as well as the nutrient value. This information will be pertinent for sheep farmers to determine whether a BSF composting system will significantly impact their available fertilizer for pasture. For farmers with limited acreage, this could be a welcome reduction in volume as they may not have to pay to have material removed.
My farm has been in operation over 5 years, and I have lived on farms my entire life raising livestock, hay, and produce. Specific to this grant, I have a flock of approximately 80 ewes, two primary animal housing units (a traditional metal barn, as well as a high-tunnel with a white plastic covering) which will represent different types of animal housing used for sheep in the industry. The animal housing is equipped with electricity that can be used for heat mats and automatic waterers which will provide water to the sheep ad libitum as well as a water source for the black soldier flies in the adult stage. In addition, there is a sheep handling system which will be used for fecal egg collection for this project. I have utilized fecal egg counts over the past few years while exploring management methods to prevent anthelmintic resistance.
The first step for this study was to prepare the black solider fly composting systems (Diagram A). Six black soldier fly composting bins were constructed and three placed in each animal housing location (sheet metal and high tunnel). The three composting bins were placed on a heat mat and a second bin containing shavings was placed on a separate heat mat. This second bin served as the drier location for larvae to pupate. Above these bins a heat lamp was hung with a wire frame attached below the bulb to serve as a warm mating location. Pulleys were also hung on which the bins could be lifted to weigh the bins as sheep manure and bedding material was added. The initial weight of the bins was recorded prior to adding any material. Bins were filled with sheep manure and bedding material. 12,000 3/4" black soldier fly larvae were then ordered and roughly 2000 larvae were added to each bin in early March.
Fly strips were hung, 3 at a time for 1 week each, from the beginning of April through the end of July (18 weeks). These were hung in both animal housing locations as well as at 3 collaborating farms. Fly strips or reports were obtained to compare the number of pest flies across management systems.
Approximately every three days: bins were weighed, the moisture analyzed (probe tested wet, normal, or dry), the temperature of the material in the compost bin was taken, the temperature of the material in the pupation bin was taken, if water was added the weight was recorded and if sheep manure and bedding was added that weight was recorded, the outside temperature was taken, and observations were recorded as well. If the material dropped below the line drawn on the inside of the bins more material was added. In mid-June a second set of black soldier fly larvae was added due to unseasonably cold temperatures. In September the remaining material in the compost bins in each location was co-mingled and a sample taken. A separate sample of sheep manure and bedding material was also collected from the high tunnel and barn. These four samples were then shipped for Compost/Amendment Evaluation analysis.
Three pasture areas were fenced off to exclude livestock from grazing on them during the Spring/Summer of 2020 to keep the pastures "clean" for this study. The areas were mowed monthly until the final portion of the study. The compost materials were added to one pasture, an equivalent weight of sheep manure and bedding materials was collected from the barn and high tunnel and spread on the second pasture (positive control), and a third pasture was left with no additional amendments (negative control).
18 weaned lambs that had been raised in confinement (off pasture) were evaluated for FAMACHA™ score and body condition. All lambs had a FAMACHA™ score of 1 or 2, and were in good body condition. Fecal samples were collected from each lamb and sent for fecal egg count analysis. Lambs were divided into three groups. Lambs in each group continued to reside in an animal housing unit with water, hay and creep feed ad libitum (Attachment D). After four weeks, fecal samples were collected from all lambs for a second time.
This proposal had 4 objectives to study controlling larval development of pests and parasites biologically using black soldier flies.
The first objective was to evaluate the ability of black soldier flies to compost sheep manure and bedding material under two barn conditions (dark sheet metal and white film high tunnel) in Maryland. The first week of March barn bedding material was added to each bin with 2000 3/4 inch larvae. Larvae quickly burrowed down into the bedding materials. At approximately 1 month large numbers of larvae "crawled out" into the pupation bins, and handful of adult were seen in late April through early May. The Spring of 2020 was colder than usual in Maryland with a frost on Mothers Day weekend. The remaining larvae in the pupation bin did not progress to the adult stage despite being on a heat mat. Additional black soldier fly larvae were ordered and added to the bins in early June. The larvae continued to mature and complete the lifecycle although the number of larvae in the boxes was not as high as anticipated. In early August, there were black soldier fly larvae of all stages in the compost bins indicating there was replication.
The reduction in mass was 35%, slightly less than the 40% reduction in studies of poultry and swine. There was not a significant different between the mass reduction from the bins in the barn and the bins in the hightunnel. There was a significant difference in the amount of water added with the hightunnel bins requiring more water than the barn bins. This is not surprising as the hightunnel bedding consistently dries out faster. It should be noted that due to the re-starting of the black soldier flies this composting took place over a period of 6 months.
The second objective was to document the fly population in lambing barns with active black soldier fly composting bins to farms utilizing alternative fly management control. Pest fly population was measured using fly strips at both animal housing units in the study, as well as 3 collaborating sites. From April to the end of July, an 18 week period in which flies typically emerge and flourish in Maryland, 3 fly strips were hung at each location for 1 week. Fly strips were preserved for counting, and any weekly fly treatment or animal movement was noted (Attachment B). The results did not demonstrate a reduction in fly population. In contrast, by not cleaning out the barn and hightunnel in the early Spring and with the lambs retained in the barn for the study longer than anticipated, the fly population was higher than usual. In addition, starlings were found in the pupation bins eating the pupating larvae and the starling population in the barn and hightunnel were significantly higher than usual.
The third objective was to analyze the residual compost material for fertilizer value compared to non-composted sheep manure and used bedding. Prior to compost being applied to pasture the three bins in the sheet metal barn were co-mingled and a sample taken for analysis. A sample was also be collected from the remaining bedding in the sheet metal barn. The same process was repeated in the high tunnel for a total of 4 samples. The samples were analyzed for Partial Organic Analysis. There were only a few differences of note. The pH of the barn bedding and barn compost was 7.5 s.u. while the pH of the hightunnel bedding and compost was 8.3 s.u. There was also considerably more nitrogen in the samples from the barn than the hightunnel. The compost samples had slightly elevated levels of nitrogen, phosphorous, potassium than their bedding counterparts. The barn bedding sample was a third of the organic matter (in lbs. per cubic yard) than the other three samples collected.
The fourth objective was to measure the fecal egg count of lambs pre- and post- exposure to black soldier fly compost applied clean pasture, and non-composted sheep manure and bedding applied pasture. Due to the re-starting of the black soldier black soldier fly larvae this portion of the study was delayed from June until the beginning of September. The lambs were approximately 6 months in age and had not previously been exposed to pasture or been given anthelmintics. All lambs had a beginning FAMACHA™ score of 1 or 2 and were in good body condition. A fecal samples was collected from each lamb and they were divided into three groups. There was no significant difference in body weight, FAMACHA™ score, or egg count between the three groups. The lambs were placed into the divided hightunnel and treatment plots for four weeks. The pasture had not been grazed or otherwise had animals on it in 2019. The negative control group pasture did not have any amendments added. The treatment plot pasture had the contents of the compost bins applied to it (149 lbs. compost). The positive control group pasture had 149 lbs. of barn bedding to which sheep did have access. At four weeks the lambs were examined again and a second set of fecal egg samples collected. There was no significant difference between any of the groups.
The results from this study were not significant enough to make recommendations on management practices.
While the first objective showed a mass reduction of 35%, very close to the anticipated 40%, this composting took place over a 6 month period rather than the 3 months originally planned. This poses a challenge to the usefulness of this method as many farms would not have separate storage for materials and not cleaning out the barn in this study showed an increase in fly pests even with the addition of black soldier flies. In addition there was no benefit demonstrated to the compost as a soil amendment. While this study did not show a reduction in parasite load, it should be noted that the positive control results did not serve as a true positive control. The non-composted sheep manure and bedding materials had also aged over the summer months rather than the planned spreading of materials from ewes recently lambing and nursing. Another factor may have been the age of the lambs, 6 months, having fully developed intestines making them more resilient.
Education & Outreach Activities and Participation Summary
Due to the outcome of the study the planned outcome was not conducted. While the composting tub did work over the warmer months for rearing the black soldier fly larvae, improvements need to be further investigated to extend the season it can be used. One potential solution to investigate would be to have more mechanical agitation or tumbling to help maintain aeration and even distribution of water since the heat mats tended to promote evaporation and the formation of a crust at the top while the rest of the material was drier than ideal. The design of the cage and the heat lamp was also flawed. Rarely were any adult black soldier flies seen on the cage. It is not clear if this is because they were not trapped and had other options, or if they did not like the building material or heat lamp.
We also would not promote this research as it did not solve the fly pest problem and promoted bird pests. As described elsewhere, the cold Spring did not allow the black soldier fly larvae to outcompete regular pest flies. There still were a large number of black soldier fly larvae that were found in other areas of the farm such as crevice's of silage bales. As a result, the abundance of flies and larvae resulted in a flourishing Starling population. While these birds are beneficial to a degree, the number has now reached nuisance levels and there is a concern about there droppings contaminating animal food and water.
For these reasons, we would not recommend farmers adapt this practice and therefore are not promoting the practice.
There were few takeaways from the results of this study. Barn cleanout in the early Spring did appear to be one factor that assisted with lower fly counts. This is typical as this is when many areas allow farmers to spread manure, but these results confirm the additional benefit of reducing pest flies. Another benefit was maintaining the lambs off pasture for longer after weaning. Even after the study all of the lambs used thrived on pasture throughout the Fall.
There is still a potential for the use of black soldier flies on farms. The composting system in this grant would need to be improved upon. The most critical improvement would be to increase the churning of the material to keep the moisture consistent and keep the environment aerobic. The larvae did appear in other places that could harbor pest flies such as grain spills under creep feeders.
More work should be done to verify that spreading barn materials on to pasture in the Spring does not introduce a high parasite load. If needed, composting recommendations should be made available.