Nitrogen Flow Characterization of Laying Hen Production Systems: Preliminary results

Abstract. Egg production systems have evolved in recent years and a better understanding of those systems is a key factor in the identification of the environmental hot spots associated with those production systems. The whole farm nitrogen (N) cycle was identified as a major contributor to the environmental impact.

The objective of the current study was to quantify N flow for the entire production cycle (barn, manure storage and land application) of a conventional laying hen farm (manure belt cage system with natural drying) and an aviary system (free-range with bedding) using a mass balance approach. The manure was considered stored on the farm and land applied following a nutrient management plan.

For conventional cage system, for every 100 g of N consumed, there were 7 g fixed by the hen, 30 g transferred in the eggs and 58 g excreted in the manure and 4 g in gas emissions. A total of 7 g of N were lost during manure storage. After storage, 51 g of N were land applied. After land application, 17 g of N were lost in gas emissions. The remaining 34 g of N were available in the soil for plant growth. In aviary system, for every 100 g of N consumed, there were 3 g fixed by the hen, 24 g transferred in the eggs and 41 g excreted in the manure and 31 g in gas emissions. A total of 5 g of N were lost during manure storage. After storage, 36 g of N were land applied. After land application, 12 g of N were lost in gas emissions. The remaining 24 g of N were available in the soil for plant growth. The main N lost difference of the both system are at the building stage where the N loses of aviary system is seven times higher and the ammonia emissions are 13 times higher.