Keeping Birds Warm and Comfortable with Dry Litter

Though controlling litter moisture is crucial for limiting ammonia production in houses, it also helps keep birds warm during cold weather. One of the key functions of litter is to protect birds from the cold, hard clay or concrete floors in a house. Essentially, the litter serves as a blanket that helps minimize heat loss from the undersides of their bodies. The R-value of sawdust is about 2.5 per inch—roughly the same as blown fiberglass, which means the floor beneath the birds is nearly as ...well insulated as the ceiling above them. You can often see birds taking advantage of the insulating ability of dry litter when they bed down in it if house temperatures become too cool.

The insulating ability of any insulator is highly affected by moisture. For instance, just a 10% moisture content of fiberglass insulation can cut its R-value in half! While no study has measured how moisture impacts the R-value of built-up litter, it’s reasonable to assume that insulation decreases rapidly as litter becomes wetter, underscoring the need to keep litter as dry as possible during cold weather. The fact that damp litter is a poor insulator is commonly demonstrated when a house is cleaned out and built-up litter is replaced with the fresh, damp, pine shavings. If the house is not properly preheated and the damp pine shavings are not occasionally turned to facility drying, chick performance often suffers due to the fact that they are being raised on a cool, damp “blanket” instead of a warm, dry blanket. Though this tends to occur more often in houses with fresh pine shavings, it can still be an issue in houses with built-up litter when it isn’t properly dried between flocks and/or during preheating (Figure 1).

Even if the chicks are placed on dry litter it is important that the litter remains dry for the remainder of the flock. If moisture builds up in litter to the point that it cakes over, it increases the difficulty of keeping birds warm during cold weather (Figures 2 and 3). A broiler generates about 5 Btu/hr of essentially waste heat per pound of body weight as it digests feed. So, 25,000 birds weighing three pounds each produce nearly 400,000 Btu/hr—the same as ten radiant brooders. We use this waste heat to keep our houses warm during cold weather. What we don’t want to do during cold weather is to remove heat directly from the bird, as can happen when the litter cakes over. While dry litter is an insulator, dense, caked litter is more of a conductor, increasing heat transfer from the birds to the floor. Try this. If you are in a kitchen with stone countertops, place your hand on a dish towel sitting on the counter. Then put your hand on the countertop. Though the towels and the countertop will be essentially the same temperature as the air in the kitchen, the countertop will feel colder because it is a conductor, allowing heat from your warm hand to be drawn into the countertop. When birds sit on dense, caked litter, heat can be drawn from the bird to the floor, making the bird feel cooler. The bird will tend to eat more feed to stay warm, resulting in a higher feed conversion rate.

The situation can become even more dire if the caked litter is damp; the birds are now essentially sitting on an evaporative cooling pad. As air moves over the floor, moisture evaporates, lowering its temperature, much as air moving through an evaporative cooling pad reduces the temperature of the pad and the air moving through it. Now the birds are not only sitting on a conductor, but on one that can be 10 degrees or more cooler than room air temperature, significantly increasing the amount of heat removed from a bird. Is it any wonder that birds tend to avoid sitting on caked litter, especially if it is damp?

To optimize bird comfort and health during cold weather, we need to ensure we are ventilating enough to keep our litter dry, maximizing its insulating ability, and minimizing the risk of ammonia formation. To accomplish this goal, minimum ventilation rates during cold weather shouldn’t be based on current litter conditions. The fact is, we don’t want to wait until litter becomes damp and bird performance is adversely affected before increasing our minimum ventilation rates; we want to operate in a more preventive mode. This is why we should base our minimum ventilation rates on the relative humidity of the air in the house. If the relative humidity of the air is increasing over time, this means our litter moisture is increasing over time. You may not be able to see it, but it is increasing.

The ideal relative humidity is between 40 and 60%. Below 40% litter can become too dry, resulting in potentially excessive fuel usage and dusty conditions. If the relative humidity is above 60%, moisture levels in the litter will tend to build, resulting in increased ammonia production and, as noted previously, the increased potential to cool the birds. Think of the relative humidity of the air as an indirect rough measure of litter moisture. The higher the relative humidity, the higher the litter moisture will tend to be and the more bird performance and health will tend to suffer.