S.E.M. Dekker

Total loss and distribution of nitrogen and phosphorus in the outdoor run of organic laying hens.

1. The objective of this study was to determine the level and variation of the total mass, and load of nitrogen (N) and phosphorus (P) excreted into the outdoor run of organic egg production systems. 2. Three egg production farms with an aviary system and an outdoor run were selected for this study. Four measurements, one per season, were executed on each farm. 3. Mean content of N and P of a manure dropping was 14·0 g N kg−1 and 3·12 g P kg−1, mean mass of a dropping was 6·36 g and mean dry matter content of a dropping was 238 g kg−1. Mean rate of excretion in the outdoor run was 2·99 droppings per hen per h. Mean percentage of hens outside during the time the outdoor run could be accessed was lowest on Farm 1 (1·7%), highest on Farm 2 (16·0%), and intermediate on Farm 3 (7·1%). 4. On all farms an exponential decrease of the number of hens and of the load of N and P with increasing distance from the hen house was found. Load of N exceeded the fertilisation standard (of 170 kg ha−1 y−1) in the region at a 0 to 19 m distance from the hen house on Farm 1, 0 to 146 m on Farm 2 and 0 to 52 m on Farm 3. 5. It is concluded that the husbandry system should be redesigned to solve the problem of overloading, unwanted loss of N and P to the environment and loss of N and P from the organic production cycle.

Gaseous Emissions From Aviaries And Nitrogen And Phosphorus Losses In The Outdoor Run Of Organic Laying Hens

Emissions and losses from animal production systems cause substantial environmental impact, e.g. eutrophication, acidification and global warming. The objectives of this study were to assess the year round emissions of ammonia (NH3), nitrous oxide (N2O), and methane (CH4) from commercial aviary systems with organic laying hens and to determine the level and variation of the total mass, and load of nitrogen (N) and phosphorus (P) excreted into the outdoor run of three commercial organic laying hen farms. Emissions were computed from the ventilation rate (CO2 mass balance) and gas concentrations. N and P losses were calculated from number of hens, mass and content of excrements in the outdoor run. Mean emission per hen was 410 mg d-1 for NH3, 3.12 mg d-1, for N2O and was 81.7 mg d-1 for CH4. Mean predicted emission of NH3 per hen on the first day after manure removal was 298 mg d-1, and increased by 5.47% d-1. Using aviary systems in organic laying hen husbandry instead of single-tiered systems has the potential to reduce emissions of NH3, N2O, and CH4. Mean percentage of hens outside was 1.7% on farm 1, 16.0% on farm 2 and 7.1% on farm 3 and. On all farms load of N and P heavily exceeded the fertilization standard of 170 kg ha-1 y-1 and decreased exponentially with increasing distance from the hen house, due to an also exponentially decreasing hen density.