Date of this Version
Data from 18 experiments (244 pen means) over a 10-year period were summarized in order to make a long term comparison between seasons dealing with nutrient mass balance studies and characteristics and amount of manure from open feedlot pens. The amount of manure DM increased from 10.6 lb to 20.0 lb/head finished/day from summer (May to September) to winter (November to May). Quantities of OM, ash, and N (lb/head finished/day) increased from 2.5 lb OM, 8.1 lb ash, and 0.13 lb N to 4.8 lb OM, 15.2 lb ash, and 0.22 lb N/ head finished/day from summer to winter, respectively. Summer pens averaged 2.7% of N excretion in pen runoff N, and 6.2% of OM excretion in pen runoff, while winter pens averaged 1.8% of N excretion in pen runoff N, and 1.9% of OM excretion in pen runoff. Average N volatilization was higher for summer feeding pens (69%) compared to winter (47%). The implications, which can be used in individualized NMPs, are more total manure and manure N must be handled, but less volatilization of N and less N runoff occur in the winter compared to the summer feeding period.