For those unfamiliar with the practice, litter windrowing is a biological heat treatment that creates low temperature pasteurization or partial sterilization of the material. Unlike composting, the basic material doesn’t change; it’s still litter at the end.

Windrowing not only partially thermally kills pathogens in the litter but also gives the floor an opportunity to be exposed to the environment and partially dry out. There isn’t a continual reservoir of wet moisture and nitrogen-rich compacted material.

There have been a number of studies on windrowing over the past 15-20 years, which have uncovered the following insights:

1. Windrowing, done properly, can reduce the bacterial and protozoan loads in poultry litter and can de-activate many viruses including avian influenza, laryngotracheitis and other poultry respiratory diseases.
2. Windrowing can improve performance on farms that have a disease challenge.
3. Windrowing is a thermal kill, not a chemical kill; when done correctly, there shouldn’t be drastically higher levels of ammonia in windrowed material.

Here’s an overview of how proper litter windrowing works, according to Casey Ritz from the University of Georgia. This summary outlines his main points made at the 2021 Midwest Poultry Federation Convention held virtually.

Before You Windrow: Some Factors to Consider

Before you start to implement litter windrowing on your farm, you need to make sure you’re prepared to take the time and invest in the resources needed to do it effectively.

For starters, windrowing takes a significant amount of time. It requires patience and a methodical approach during each step:

• Forming the piles
• Turning the piles
• Leveling the floor
• Leveling the litter
• Preparing the house prior to chick placement

You’re dealing with live organisms inside the microbiota, so allow time for the process to complete. Rushing the process can not only render the process ineffective, but can create additional problems like high ammonia levels.

However, the specific amount of time you need varies from flock to flock. So be prepared to spend time taking internal temperatures and test the material to determine exactly how long the process takes on your farm. Generally, this ranges from 12-14 days.

Also, be aware of ammonia volatilization, which can present problems both for the animals and their caretakers. The biggest drivers of ammonia are temperature, air turbulence, pH and moisture.

To retain ideal temperatures and promote microbial growth, 4-6 inches of litter is needed, which allows for material to be insulated. Too much material, however, can make it difficult to regulate temperature throughout the windrow.

Moisture is one of the biggest factors to monitor. Without proper moisture, bacteria populations cannot regenerate quickly. Therefore, good windrowing retains some moisture, oxygenates the litter and uses temperature to wake up the microbes. Too much moisture, however, leads to ammonia. It’s all about finding the right balance.

All in all, how you windrow will depend on the specifics of your flock. While there are guidelines you need to follow, trial and error is best to figure out how this will work on your farm.

Guidelines for Effective Windrowing

Although there are specific variations in the process, generally windrowing follows a few specific guidelines.

First, as mentioned above, this process takes time. In terms of the overall commitment, you’re looking at 1 hour to create the windrows, and 45 minutes to level them, per house. There’s also the time it takes to wash and maintain all of the necessary equipment, set up and maintain proper ventilation and more.

After the formation of the windrows, you should wait 2-4 days to turn the material. Most of the time, that’s long enough to achieve temperature goals.

You should also turn the materials as many times as you can afford to do. This has two benefits:

1. Maximize the amount of litter that reaches the higher temperatures
2. Allow as much floor area to dry as possible

For producers new to the windrowing process, it’s good to monitor internal temperatures to ensure that you’re reaching the necessary levels. The core of the windrow should reach around 130 degrees, which is the threshold for pathogen survivability.

Finally, it’s important to actively manage ammonia levels during the windrowing process. The presence of wet material provides ample opportunity for ammonia volatilization, which may require the addition of litter to suppress those levels. Proper ventilation is also critical, especially under cool weather conditions.

Generally speaking, ammonia becomes more manageable after a few flocks, particularly as you get used to the windrowing process and the end result. Thus, it’s probably a good idea to start a program in moderate or warm weather.

Keep in mind, for many farmers, it takes several consecutive flocks of windrowing events before they see a reduction in disease challenge or recurrence. So it’s not a silver bullet solution.

The Potential Benefits of Windrowing

While it’s difficult to get exact economic figures in terms of the impact of windrowing, at the very least pathogen reduction can be a major cost saver. There are certainly challenges, equipment costs and labor investment.

But considering how much you could save in terms of disease impact, you should consider that it may be worth the investment.

Windrowing isn’t 100% effective, as it’s not sterilization of the litter, nor an ammonia control program. But if done right, it’s an excellent tool to have in the litter management toolbox.