GASEOUS EMISSIONS FROM ALTERNATIVE HOUSING SYSTEMS FOR LAYING HENS F. da Borso, A. Chiumenti, T. Rodar Dipartimento di Scienze Agrarie e Ambientali, Università degli Studi di Udine, via delle scienze, 208, 33100 Udine, Italy. daborso@uniud.it ABSTRACT Laying hen housing systems imposed by the 99/74/CE Directive are conceived to improve welfare of laying hens, so they could express natural behaviours, such as bitter-scratching, dust-bathing, egg-laying on nests. However, recent researches on enriched cage systems and deep-litter systems pointed out some negative aspects, like a worse egg quality, because a lot of eggs are laid out of the nest and are frequently broken. The Department of Agricultural Science and Environment, University of Udine, in the frame of a rese- arch project co-financed by the Ministry of University and Research, carried out several experimental trials in alternative houses with deep-litter system in order to assess the environmental impact. Egg production from alternative houses was similar to that generally obtained from conventional cage systems, but hygie- nic, behavioural and management problems were pointed out. In alternative houses, higher ammonia and dusts concentrations were found, distressing hens, workers and environment. Ammonia emissions, calculated from gaseous concentrations and ventilation rate, ranged from 0.239 and 0.427 kg unit -1 year -1 . According to the Best Available Techniques reference document of the IPPC EC Directive (ILF BREF, 2003), the deep litter systems for non-cage housing of laying hens could not be clas- sified as BAT, due to the high emission levels. INTRODUCTION In Italy the poultry sector is subject to several laws which involve enviroment protection (water and air pollution), welfare and sanitary aspects. In particular D.lgs 29/7/2003 n.267, adopts directives 99/74/CE and 2002/4/CE, about laying hens welfare, and D.lgs 4/8/1999 n.372 partially adopts the directive on Integrated Pollution Prevention and Control (IPPC). The present study aims to point out some results obtained from experimental trials on alter- native deep-litter systems for laying hens, conformed to 99/74/CE, in order to assess their gase- ous emissions and environmental impact. In the frame of the National Project “Innovazione tecnologica degli allevamenti zootecnici” co-financed by the Italian Ministry of University and Research (MIUR), a preliminary investi- gation was carried out in order to focus on the Italian situation about alternative housing systems. Up to now, in Italy only one livestock unit adopted furnished cages, but the deep litter systems are more diffused. However, the interest for the deep-litter systems is more related to the eggs’ marketing rules (1274/91/CE) and to the organic production rules, than to the obliga- tions from 99/74/CE directive. Several experimental trials were carried out in alternative houses in order to record constructive, management, productive and sanitary data and to deep on envi- ronmental impact. The present paper aims to focus on this last aspect. MATERIALS AND METHODS Two units were selected, fulfilling the requirements of directive 99/74/CE as regards deep- litter systems: more than 1/3 of the floor area was covered with litter material and the remaining 337 Gaseous Emissions and Odours