Integrating ducks into log-grown shiitake mushroom production for slug control and added yields

Final Results

We achieved many good results, some based on observation and some on data. The first result is that ducks provide a significant level of pest control throughout the farm (including forests, fields, and gardens) and, if rotated, do not appear to have adverse effects on the landscape.

Of the ducks we raised for meat, only the Muscovy gains sufficient weight to make a profit and a duck would need to gain at least 8 lbs in a season to make it economical under our model. Given feed costs and market prices, and depending on a farmers slaughtering capacity, a range of 150 - 400 ducks would need to be raised per season to be economically viable.

Bringing the ducks into contact with the mushrooms did appear to have a positive effect on reducing slug populations, though the mix of variables (weather, temperatures, labor, etc) made it difficult to collect good data on this relationship.

We will offer our final results including our summary observations and any relevant data by revisiting each of the three main questions this study sought to answer.

1. Are ducks effective and reliable slug control in log-grown mushroom cultivation?

Summary Observations

From this study, we were unable to collect conclusive data on if ducks offer a viable means to reduce slug infestation on shiitake mushrooms because of variables and unpredictability in weather, precipitation and temperature. However, our observations did lead us to believe that the presence of ducks in the vicinity of fruiting mushroom logs can help but not entirely eliminate slug pressure on a shiitake crop. Ducks are not the perfect solution, but rather a supplement to other strategies including the removal or organic matter from the fruiting area, placement of gravel under logs, use of beer traps, and daily monitoring.

In 2012, the drought conditions meant the mushroom yard had very low slug pressure. We saw some slugs toward the end of the summer and at the same time observed that ducks were effective at slug control IF mushroom logs are located near to duck food, water, and housing.

In this same year, we had almost 0% slug damage in the Muscovy/Rouen pen, but only after the fruiting logs were fenced off because the Muscovy would actually take large bites from the mushroom.

The fruiting area in the Cayuga/Swedish Blue pen was probably located too far away from food/water/shelter of the ducks and slug damage was comparable to the control. It seemed that the ducks did not spend that much time near the logs and thus did not feast on the slug population.

In 2013 we had a much wetter season and with this saw the rise and fall of slug pressure. Since we rotated the ducks weekly this season, we did not have the ducks continuously grazing near the mushroom logs. As such, we created three levels of interaction: The Control (no duck visits), Light Interaction (two visits in the season) and Heavy Interaction (ducks constantly in or near mushroom yard). The Control yard most certainly had the most slug activity. The Light area had ~ 50% less observed slug activity, and The Heavy area had very little slug activity.

As we suspected, and now observed, slug populations directly relate to moisture/weather. A further fact is that slugs don’t have eyes, and thus attracted to the mushrooms by smell as they open up and release spores. Removing slugs from the general area when mushrooms were pinning proved to be helpful. If precipitation patterns are timed with soaking mushroom logs, and subsequently mushroom fruiting, high slug pressure may be avoidable, but certainly it will vary from year to year depending on weather. Though we are just starting to test this out in our system, these cycles and timings may important for the shiitake grower to take note of in order to lessen overall slug damage on fruiting mushrooms.

A final key point is that the presence of ducks in the woods does two things: first, it decreases organic matter which is ideal habitat for slugs, and two, it directly reduces the ability of the population to both move in toward the mushrooms as well as build up a population. In conclusion from our observations, it did not appear to be important to have ducks in a particular place at a particular time. If they can be rotated around the area that the mushrooms are produced, there will likely be some benefit for the farmer.

Data/Documentation

We had a difficult time collecting good data to support our observations for a number of reasons. In 2012 we tried to calculate the percent of damaged mushroom caps vs. perfect caps in the three laying yards, but found that this assessment is subjective and that, since there are other causes of damage (weather, rodents, farmer, transport), it was hard to ensure that damage was from slugs and not other factors.

In 2013 we attempted to switch our collection methods and tried collecting and weighing the slugs that were found in the general vicinity of the log fruiting rack. This proved to be challenging, as it took an incredible amount of time and just because a slug is in the mushroom laying yard does not mean that slug will damage a mushroom cap. Further, on several occasions, even a day after a sweep of the area, the slugs were present on the mushrooms and would take constant monitoring of the yard to be effective. Balancing the need for monitoring with the realities of farming (not to mention that picking up slugs one by one and weighing them is rather disgusting), we did not continue trying this method for too long.

All this being said, there were two definitive indicators that offer evidence to support that foraging ducks near a mushroom laying and fruiting yard is worthwhile to control slug pressure:

1. Average slugs/log

On two occasions in 2013 we were able to sample ten logs from each laying yard and count and average the slugs/per log for each area. This was done during a wet period when overall slug activity was high and when timing allowed for this to work. While this isn’t enough data for anything conclusive, it does offer some suggestive evidence of some benefit.

Average slugs per log for two random dates in 2013           

2. No mating pairs

One positive outcome of the study was that no mating slugs (see image below) were found in the mushroom area with ducks heavily grazing around versus many dozens found during wetter parts of the growing season in the control area and a few in the light area. This was a constant observation made on a weekly basis throughout the season. While this doesn’t directly relate to damage, the ability of a population to reproduce is arguably one indicator of overall population success.

2. Is the forest affected in any negative way from the presence of ducks?

Summary Observations

The presence of ducks in the forest has one critical impact observed; leaf litter from the previous fall decomposes much more quickly when animals are in the forest. In some areas of the woods, particularly where water pooled and flowed during heavy rain events, grazing appeared to create bare ground and mild compaction, which led to some minor erosion. This impact was much more dramatic in year one when the stocking rates were high (50 ducks continuously in a 1/3 acre paddock) versus year two, where smaller flocks of 25 were rotated in smaller, ¼ acre paddocks.

One good strategy to balance the trampling of organic matter was to time the cleaning out of the duck houses so that the straw and manure accumulated was removed just before the ducks were moved to a new location. It is recommended that additional organic matter is available to be added to a forest grazing system. In the future we plan to monitor nutrient content and percent organic matter in our soils to get a better grasp on potential benefits or harm from grazing animals.

In 2012, we let the ducks forage in one area continuously. As a result, there was noticeably less forest litter and in some case bare ground due to the movement of the duck flocks. (see picture, above). In the Muscovy/Rouen pen this was especially the case. In this regard, continuous duck presence had a negative effect on forest health. As a result, and to keep more inline with our farm goals, in 2013 ducks were rotated weekly between different plots in the pasture and the forest.

We observed ducks to forage understory vegetation at will. This could be both a positive and negative thing depending on understory vegetation. Another positive impact was the large amount of manure left in the forest. We realize in hindsight that it would have been great to sample the soil and the beginning and end of the season to get a comparison. We will begin this practice in 2014 to help better understand the impact. Also in 2013,rotating the ducks once per week and using a smaller paddock size improved the impact of the ducks on the forest. In some cases, however, the ground and leaf litter was significantly reduced with even just a short stint of the ducks.

Data/Documentation

No data collection was attempted for this question. Perhaps soil testing or some sample plots could have been monitored.

3. Are ducks economically viable as an additional income stream?

Summary Observations

The simple answer to this question from our experience is “yes”, if a farmer is willing to greatly scale up flock size. To be an economically viable duck meat farmer production would need to be a primary goal, not a byproduct of a desire to control slugs and enhance an ecosystem. In the context of a small woods (about 1 acre) and a 1,000 log shiitake operation, a flock of 20 to 25 ducks is plenty to maintain some degree of protection from slugs, including some time rotating in gardens and fields, too. This size is NOT viable for meat production.

The good news for those interested in raising hundreds of ducks for meat (see below) is that the market demand is very high (at least in our region). It should be noted that we sold to restaurants and a retailer who cater to customers in a market of customers willing to pay more decent prices ($5 – 6/lb) for sustainably raised and local meats.

In 2012, the chef at the restaurant we sold our birds to was happy with the product and sold out of them within two days on the menu. There is clearly a demand in this market. This restaurant, as well as several others, told us they wanted more duck and have a hard time finding it. With regards to specific breeds, this particular place (a small restaurant in rural New York, with 50 seats, serving as much local food as possible for $15-30/plate) felt the Muscovy were a bit too big and preferred the birds that were 5 – 6 pounds (finish weight), which is a about a pound larger than we could get the heritage breeds to, but under the finish weight of the Muscovy.

Further, when considering economics it is challenging to quantify the value of fertilizer the ducks provide to the system, along with the benefits of slug control. We are finding that the ducks are proving valuable not only in the woods, but in our gardens and around planted tree crops as well. In 2013, our garden saw little to no slug and bug damage to plants, and the ducks also performed well when given access to cover crops we had sown as part of a soil building protocol. It is also our observation that the Khaki Campbell and Cayuga’s, are better foragers and less interested in grain than the breeds more ideal for meat production.

Data/Documentation

Weight Trends

We can examine trends in weight gain from the ducks. In 2012 we randomly weighed three ducks once/week from late June through early October. The entire dataset and averages per week are presented below.

Notable is that there is a decent amount of variation among the duck weights from week to week. The Muscovy is the only breed that had solid growth over the course of the season. Most of the other breeds could arguably be slaughtered much earlier in the season since they appeared to reach average max weight in August.

Important to note in this trial is one aspect of a poor experimental design, where the Rouen/Muscovy were lumped as were the Swedish Blue/Cayuga. While the latter group appeared to share their food and finish throughout the day, the Muscovy dominated the Rouen flock and ate far more than their fair share. Either way, it is clear that if weight gain is a clear goal for commercial meat production, then Muscovy is the choice from these breeds.

Feed costs

A second metric with consideration for meat production is feed cost, since it impacts potential profit. Our strategy was to feed the ducks “free choice” for the first eight weeks of their life and then transition to a ration, based on the recommendations of books. In 2012 we provided a maximum amount of .2 lbs/bird twice each day (.4/lb/bird total) and did not rotate their pens, whereas in 2013 we cut that amount by 50%, feeding only once a day at a rate of .2lbs/bird though rotated them weekly.

Based on the number of ducks, we calculated the cost of feed per day for the first eight weeks and then did another calculation for the remaining time until slaughter. Since the rationed feed was cut in half the second year, the cost per bird is roughly half from one year to the next.

Costs of feed

The interesting analysis comes when we looked at the potential profits based on the weight gain and price per pound we got. For this we removed the Muscovy ducks from the dataset because we did not have them in the second year, and all the other ducks were in a similar weight class. This worked well because it made the number of ducks in the sample size equal, since we did not harvest all 50 the second year.

Potential Profit for Medium Weight Breeds

Potential Profit for Muscovy

We were pleased to see that cutting the feed in half and rotating the ducks weekly led to only a very small decline in average weight per bird. (keep in mind we didn’t raise Muscovy when we did this - this may not be the case for the larger meat breeds) We can say for certain that for Cayuga and Rouen, more feed did not contribute to more weight gain, and in fact resulted in some net profit, at least when only feed is taken into consideration.

The $7.70 in profit is just taking into account feed costs. When we consider other costs, the potential looks less optimistic. For one, in both seasons we took the ducks to a certified facility, as we lacked the space and infrastructure to slaughter on farm properly. Furthermore, to sell to the outlets we chose (in 2012 a restaurant and in 2013 a butcher shop), New York State law requires that we process at such a facility. It cost $4/duck to slaughter and package, which means that we have a further loss in potential profit per bird in 2012 and reduce our potential profit to $3.70/bird. Furthermore, we also have to subtract the cost of a duckling from this number, which was $5 per bird. In the end, considering the costs of feed, slaughtering, and ducklings, a total potential profit in 2012 was $1.30/bird for the medium weight breeds and $21.44 for the Muscovy.

One point of good news for those interested in ducks for meat is that the heritage birds appear to gain their maximum weight early in the season and then level off. This means that smaller breeds could be raised on shorter rotations, which may improve their profitability since feed costs, time and labor would all be less. We found that a 3 – 4 pound duck (finished weight) was acceptable to some customers and though not very large, very delicious and can provide a sizeable meal to two people. The breasts and legs from one bird are a good serving size for two people, with the carcass making a fine stock. If a farmer can find markets willing to purchase smaller heritage birds, she/he may be able to find a profitable niche.

Other costs: Infrastructure

Of course, feed and slaughter costs were not the only costs. Over the two years we spent a considerable amount of money on the facilities to house, feed, and provide water to our duck. Certainly many of these expenses are capital requirements that are beneficial for the long-term and not recurring annually. In this case $2,950.29 (see next page) of materials and supplies can be spread out over say, ten years, or $295.29 per year. To cover feed costs (above) and break even on infrastructure costs, a farmer would need to raise about 15 Muscovy ducks per year for ten years. If we raised around 150, then we could pay this infrastructure off in a season, and begin making profits in the second year. This is a viable and realistic option for meat production; however, these numbers do not take into consideration time/labor.

Labor

The above figures do not include accounting for our time. We consistently spent an average of 30 minutes a day on chores, which equals 64 hours in 2012 and 58.5 in 2013. Add another 40 total hours on building, repairs, etc. This is a total of 100 hours of labor. At $12/hour, this is another $1200 to the total cost. This means that raising Muscovy ducks for meat, a farmer would need to add another 60 ducks per season to break even.

Financial Summary

The total costs to raise ducks for meat appear to be approximately:

$20 per bird for feed (for meat breeds that gain sufficient weight)

$5 per bird for duckling

$4 per bird for slaughter

$3000 in start-up costs ($300/year)

$1200/year in labor

If an 8-pound bird can be sold for $40 ($5/lb), then 150 birds would allow for a break-even including labor over ten years, while raising 420 birds would pay off the costs in a single season. The calculations we have provided are based off 50 birds, and relatively minimal numbers with regard to labor, material, etc.

• Duck Weight Graph – 2012