Mortality composting for small ruminant producers

This article discusses the benefits of composting small ruminants and how to do it.

Skid steer working with compost.
Skid steer working with compost.

Unfortunately, mortality is a reality of any livestock operation.  But is it possible to turn this loss into some form of gain?  The answer is yes!   “The Bodies of Dead Animals Act” (BODA); Act 239 of 1982 and as amended (see is Michigan law that stipulates legal means of mortality management.  Under BODA, there are six alternatives to disposal including: burial, incineration, rendering, landfill, composting and anaerobic digestion.  Composting is covering the carcass in a carbon source (sawdust, chopped straw, woodchips, dry bed pack, wasted feed) and mixing it all up periodically, to provide a great place for microorganisms to work on decomposing the carcass completely. Composting is a relatively cheap option that is easy to do and comes with the added bonus of providing quality, slow-releasing fertilizer than can integrate well into a grazing operation.  Composting can be done in a manner that prevents runoff and leachate, and controls odors, flies, rodents and other pests.

For smaller scale farm operations, defined by 20,000 or fewer pounds of mortality per year (nearly all sheep flocks fit this description), composting can be done simply and efficiently in small piles or windrows.  Location is important, and a discrete place at the edge of a field is preferable.  It must be a minimum of 200 feet from waters of the state, neighboring residences, and wells, in addition to being at least 2 feet above the seasonal water table (BODA, 2008).  New sites must be identified every year and compost may be left there for another year to finish the process.  The important principle is that you use the site for crop production after two years, thereby using the nutrients that accumulate in the soil beneath the piles.  You can return to compost on a previous site after a 10 year rest period.

Compost methods vary but need not be elaborate or expensive.  Small operations can get started by simply placing material in piles or windrows and turning it periodically with a front-end loader. Understanding the compost process is important in optimizing decomposition conditions to hasten the process.  Three major factors influence the compost process:

  • Aeration – Incorporate air into the material. The idea range within the pile is 5-20% oxygen, which can be done by keeping the pile from becoming too tall (6-8 feet maximum), not using bulking material that is either too fine or too bulky, and rotating it.  This air keeps those anaerobic bacteria working throughout the pile.
  • Nutrient balance – Add carbon with bulking agents (wood chips, straw, leaves, and poor quality hay). These are sometimes called the brown material which is high in carbon and in contrast to more green plant material or animal remains which are high in nitrogen.  The ideal starting carbon to nitrogen range of the total bulking material is 25:1 to 30:1.  For sheep, a good rule of thumb is to use 1 cubic yard of bulking agent per 100 lbs carcass.  Multiple animals can be in the same pile, but try to keep 1-2 feet of material surrounding them for proper decomposition.
  • Moisture content – Add water or cover pile to control moisture content. The ideal range is 40-60 percent moisture. Generally, the bulking materials should be moist to the touch, but not form a stable ball or drip when squeezed by hand.  When initially wetting the pile, keep in mind that the carcass will leak fluids as it starts to decompose.

To monitor the decomposition progress, simply take the pile temperature. The ideal temperature range for decomposition is 100-150°F.  The pile may be rotated after it has been at least 100°F for one to two week and has reached 130°F at least once.  If it does not achieve these temperatures within a few days of forming it, check the aeration, nutrient balance, and moisture content as described above and adjust accordingly.  The compost must be turned at least 2 times (3 times to achieve >130F) before finished and able to spread.

Establishing a permanent pad for composting may make the procedure more efficient and environmentally-sound.  It also provides a more permanent place for composting around the farmstead, thereby avoiding the use of cropland for this purpose.  Natural Resources Conservation Service (NRCS) funds are available to establish compost pads; check with your local NRCS office for eligibility requirements.

Benefits of compost

In general, composting has distinct advantages. Composting:

  • Results in a soil amendment containing nutrients for crop growth.
    • Slower rate of nutrient release compared to most synthetic fertilizers, which lowers leaching potential to environmentally sensitive areas.
    • Compost is easily incorporated into the soil, providing other soil structure benefits, such as improving porosity and water infiltration.
  • The volume of carcasses and carbon sources are reduced by 50 percent or more.
  • Kills weed seeds, parasites and pathogens under sufficient heating conditions (>130 ̊F for three days).
  • Odors are minimized and carcasses are reduced to nothing more than a few clean brittle bones.
  • Can be less expensive than other methods, such as incineration, burial, or rendering.
  • Avoids burial in areas where groundwater may be close to the soil surface.

Composting for grazing operations has specific benefits. The process:

  • Is harmless to established pasture.
  • Minimizes the impact of waste application on forage intake of grazing animals, as it odor and palatability issues are minimal.
  • Reduces risk of waste incorporation into stored forage.
  • Builds soil organic matter, enhances soil structure and water retention to minimize the “summer slump” period of reduced pasture growth.

When should you apply compost?

Application during late summer, typically during a dry period, minimizes the risk of soil compaction that is always possible with heavy application equipment.  Hoof action, freeze/thaw cycles and dispersal by precipitation will facilitate incorporation into the soil surface layer throughout the fall and winter.  This also minimizes the risk of waste contamination in forage that might be harvested from these fields the following spring.

Trade-offs to consider when evaluating compost maturity versus the timing of application

Factors that influence this decision include:

  • Size of composting area
  • Expense of compost processing
  • Effect of compost maturity on forage intake of grazing animals
  • Compost nutrient leaching potential
  • Window of opportunity for application

Compost applied to pastures should be mature or finished, so that grazing of the pasture by animals is not inhibited.  Add mature compost to pastures that are part of an active grazing rotation.  Apply less mature compost to new seeding areas to protect them from excessive grazing while providing a relatively safe nutrient boost to aid in stand establishment.

Choice of application rate and area

Focus on applying compost to areas of low soil fertility that need soil building (depleted nutrient profile, poor structure, low organic matter content).  In most grazing programs, these will be areas there were once erosion prone, as well as areas that have had substantial machine harvest of excess forage.

Composting is not complex. The process can start today and let nature work for you in converting farm waste into an asset and ensure that your grass and operation are indeed, greener!

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