There are several factors that affect the amount of bedding needed for pre-weaned calves including the amount of milk or milk replacer fed, weather conditions, and bedding material characteristics. Understanding these factors and how they interact will help you manage bedding for your pre-weaned calves to enhance their comfort, health and growth.
Listed below are 13 bedding factors to be considered when selecting organic bedding.
- Water retention & evaporation rate
- Structure integrity
- Carbon content
- Carbon availability
- Animal health impacts
- Animal comfort
- Air quality impacts
- Pathogen presence
Which factors do you consider beyond availability and cost? Absorbency or water holding capacity and structure are important too. Carbon content and availability were included for those who compost used bedding. If your pre-wean calf performance is not meeting the Dairy Calf and Heifer Association gold standards of pre-weaned calf health listed in Table 1, you may want to reassess your calf management program including your bedding selection and use.
In cold weather, deep, clean and dry bedding is recommended to keep calves clean, dry and insulated from cold and wet manure, floors and air. Bedding absorbs water and feces and becomes wet and soiled over time. Clean, deep bedding that allows calves to nest helps reduce heat loss to the environment by preventing their hair coat from becoming wet and matted. Bedding that can be fluffed and retains its structure allows more nesting.
Roughly 80% of the water consumed by calves is returned to the calves' environment as urine, respiration and sweat. So if you increase the amount of milk or milk replacer fed you should expect more urine added to the calf pen. And if calves produce more urine, you need to use more bedding to absorb the urine if you want to provide a clean dry place for calves to lie down.
You might ask why the moisture cannot drain away. Urine and spilled water cannot drain away if the calf barn has a concrete floor or packed earth. Some people have floor drains or ground limestone under their bedding. While floor drains and ground limestone are good ideas they are not as effective because the bedding has to be extremely wet for liquid water to drain out of the bedding. Think of wet bedding like a wet towel. The towel has to be extremely wet, too wet for good calf comfort, for water to drain out of it. You can wring out a wet towel to get water to drain out but you still have a damp towel that is too wet to prevent wetting your skin.
Another way to remove moisture from bedding is to evaporate it and remove it with ventilation air. The recommended winter ventilating rate is based on moisture control, so why not increase the ventilating rate and remove the extra water by ventilation? Unfortunately for ventilation to remove water or urine, the water has to be converted by evaporation from a liquid to a vapor. And to evaporate water, it needs to absorb energy to go from being a liquid to a vapor. In hot weather that heat can come from warm animals or warm air.
So in warm and hot weather, ventilation air can dry wet bedding. In cold calf barns the only energy sources are the calves and they do not generate enough energy to evaporate water. The difficulty in drying things in cold weather was brought home to me in a presentation on natural grain drying by Ken Hellevang at North Dakota State University. He pointed out that grain farmers do not use natural air drying when the air temperature gets near freezing. When he said that natural air drying is not done at cold temperatures, it hit me; when temperatures get near freezing we cannot dry wet bedding in dairy barns without adding heat. For grain drying, they wait until temperatures get back to 40° F or they add supplemental heat. But providing supplemental heat is generally too expensive for calf barns.
Agricultural Research Service researchers recently reported on the water holding capacity of seven organic bedding materials commonly used in livestock facilities. The materials included corn stover, soybean stover, wheat straw, switch grass, paper, corn cobs and three wood materials: green cedar, dry cedar and kiln-dried pine. They also used three different particle sizes: fine, medium and course. Their results indicated that fine bedding materials held more moisture than medium or course materials. Unfortunately fine materials do not fluff as well to help with nesting. Wheat straw and corn stover had the highest water holding capacity while switch grass and corn cobs had the lowest.
So during cold weather be sure to provide adequate clean and fresh warm milk, starter and water but be prepared to increase bedding use to maintain deep, clean and dry bedding too.
Table 1. Dairy Calf and Heifer Associaton Gold Standards of Pre-Weaned Calf Health (2011).
|24 hours to 60 days old||< 5%|
|Scours (percent treated)|
|24 hours to 60 days old||< 25%|
|Pneumonia (percent treated)|
|24 hours to 60 days old||< 10%|
|24 hours to 60 days old||Double birth weight|
|Amount||15% of body weight within first 2 hours|
|Bacteria count||< 100,000 CFU/mL|
|Other attributes||Free of disease, blood, debri and mastitis|