An over-wintering, cow-calf beef herd produces manure‚Äîquite a lot of it. In one day, the average 1,250-pound beef cow produces 75 pounds of manure and urine. This manure has approximately 0.31 pound of nitrogen (not all of this is retained), 0.19 pound of phosphate and 0.26 pound of potassium. The feeding method beef farmers use to deal with this nutrient resource can have a positive impact on their forage and other crop production system. Care should be taken to not overfeed in an area. Too great of an accumulation of wasted hay and manure can have a negative impact on forage yield next year.
There are four basic approaches to feeding the cow-calf herd over the winter:
- Dry lot feed yard.Confining and feeding cattle in a dry lot pen from October through April, or later. Cows are fed daily and nutrients accumulate in manure/straw pack over the winter.
- In-field bale feeders.Bale feeders are placed in a field with frequent relocation of the feeders to better distribute manure and waste feed nutrients and avoid sod damage.
- Bale processing.Unrolling or grinding and spreading one large round bale at a time in a windrow on the ground, or packed snow, out in a field. The feeding site is moved each time to allow waste feed and manure to be evenly distributed across an area.
- Bale grazing.Bales are set in place in a field in the fall. They can be pre-arranged by forage quality. Cattle are allowed gradual access to the bales on a planned schedule by moving temporary electric fencing.
What becomes of the nutrients from cattle manure and wasted feed under each of these systems? According to University of Wisconsin Extension's publication, "Guidelines for Applying Manure to Cropland and Pasture in Wisconsin," as much as 50 percent of the total nitrogen and phosphorus and 40 percent of the potassium may be lost from manure on an open lot through volatilization, runoff or leaching. Up to 40 percent of the nitrogen and from 5 to 15 percent of the phosphorus and potassium may be lost during daily hauling and spreading. Much less of the nutrients are lost when cattle are winter fed in-field.
Bart Lardner from the CanadianWestern Beef Development Centerconducted research on this issue in 2003-2005. His paper, "Winter Feeding Beef Cows - Managing Manure Nutrients," states there was a definite difference in capture and utilization of manure nutrients between beef winter feeding systems. His conclusions include:
"Significant benefits can result from winter feeding beef cows on preselected sites due to increased capture and utilization of manure nutrients. Deposition of nutrients with cows versus machinery indicates more efficient cycling of nitrogen for subsequent pasture growth. In this study, economic calculations favored infield feeding. Cow cost per day was lower for field feeding than wintering cows in dry lot pens. Feed costs were similar between the systems, but field feeding had savings in machinery use and manure handling costs. Results also indicate that benefits from wintering cows on feeding sites can be managed to reduce daily costs with minimal impacts on cow performance."
In effect, the most desirable winter feeding systems with regard to manure nutrient retention and recycling (in order of efficiency):
- Bale grazing
- Bale processing
- Dry lot feeding
In-field bale feeders were not included in Lardner's study as a separate feeding system type. It is reasonable to assume the effect on manure nutrient retention would be better than the dry lot feeding system if the bale feeder was moved frequently over a large field area.
There are certainly some cow-calf farmers who feed their herds over winter in dry lot settings and do not scrape, haul and spread the accumulated manure in spring. This practice results in wasting manure nutrient resources and may present a situation posing risk to nearby surface and groundwater resources. Investment in machinery (e.g., manure spreader, bucket loader) to facilitate scraping, hauling and spreading dry lot manure should be considered.