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A B S T R A C TThe environmental impacts of livestock production are attracting increasing attention, especially the emission of greenhouse gases (GHGs). Currently, pork is the most widely consumed meat product in the world, and its production is expected to grow in the next few decades. This paper deals with the production of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) by animals and by manure from pig buildings, with a focus on the influence of rearing techniques and nutrition. GHG emissions in piggeries originate from animals through CO 2 exhalation and CH 4 enteric fermentation, and from manure through the release of CO 2 , CH 4 and N 2 O. The level of the CO 2 exhalation (E-CO 2, pig ) depends on the physiological stage, the body weight (BW), the production level and the feed intake of the animals concerned. Enteric CH 4 (E-CH 4, pig ) is principally related to dietary fibre intake and the fermentative capacity of the pig's hindgut. Based on a review of the literature, the following equations are proposed in order to estimate E-CO 2, pig (in kg day À1) and E-CH 4,pig (in g day À1 ) for fattening pigs: E-CO 2,; E-CH 4,pig = 0.012 Â dRes; with BW (in kg) and dRes for digestible residues (in g day À1 ). Numerous pathways are responsible for GHG production in manure. In addition, the microbial, physical and chemical properties of manure interact and modulate the level of emissions. Influencing factors for removal systems for both liquid and solid fractions of manure have been investigated. A large range of parameters showing an impact on the level of GHG production from pig houses has been reported. However, few of these can be considered unquestionably as GHG mitigation techniques because some strategies have shown contradictory effects depending on the gas, the circumstances and the study. Nevertheless, frequent manure removal seems to be an efficient means to reduce concurrently CO 2 -, CH 4 -and N 2 O-emissions from pig buildings for both slatted and bedded floor systems. Manure removal operations may be associated with specific storage conditions and efficient treatment in order to further reduce emissions. Several feeding strategies have been tested to decrease GHG emissions but they seem to be ineffective in reducing emissions both significantly and durably. In general, good management practices that enhance zootechnical performance will have beneficial consequences on GHG emission intensity. Taking into account the results described in the literature regarding CO 2 -, CH 4 -and N 2 Oproduction from animals and manure in pig houses, we estimate total GHG emissions to 448.3 kg CO 2 equiv. per slaughter pig produced or 4.87 kg CO 2 equiv. per kg carcass. The fattening period accounts for more than 70% of total emissions, while the gestation, lactation and weaning periods each contribute to about 10% of total emissions. Emissions of CO 2 , CH 4 and N 2 O contribute to 81, 17 and 2% of total emissions from pig buildings, representing 3.87, 0.83 and 0.11 kg CO 2 equiv. per kg carcass, re...

The increasing public concern for animal welfare has pushed the poultry sector to progressively replace conventional battery cages (CC) for laying hens with alternative systems such as enriched cages (EC) and aviaries (AV). The aim of this study was to compare laying performance, egg location, and egg quality associated with these three housing types. The experiment was conducted in twelve pilot-scale chambers fitted out with one of the three treatments. Each chamber housed 30 Lohmann LSL-Lite laying hens from 23 to 32 weeks of age. The available area was 492, 780, and 1120 cm²/hen for CC, EC, and AV, respectively. The EC and AV chambers were equipped with nest boxes, perches, and a pecking/scratching area (PSA). In the AV chambers, hens had free access to a space arranged in three levels with a wood shaving litter on the ground level as a PSA. Hen-day production was recorded and egg quality assessment included egg cleanliness, weight and proportion of each component (albumen, yolk, and shell) but also pH, Haugh unit, and meat spots for albumen; color intensity and blood spots for yolk; thickness and resistance for shell. The laying rate and egg weight were similar for CC and EC (around 96.5% and 59.5 g; P > 0.05). For AV, these parameters were significantly lower (77.2% and 58.6 g; P < 0.001) but the differences compared to the cage systems progressively reduced across time. Nearby 70% of the eggs were laid in the nests with EC while almost all of the eggs were laid on the litter at ground level with AV. The rate of clean eggs was around 77% for both cage systems compared to 14% for AV. Most of egg quality traits were identical for the three systems (P > 0.05) but there was a lower yolk proportion for eggs laid in AV (25.2% versus 25.7% for cages systems; P < 0.001) and higher shell resistance for eggs laid in CC (40.7 N versus 39.3 N for alternative systems; P < 0.001). Lower laying performance observed with AV could be explained by higher animal activity and competition for facilities, but these factors were not measured in this study. The reduction of the difference in egg productivity over time compared to cage systems suggest the need for a period of training/ adaptation for pullets/hens kept in such an environment. An enriched cage system seems a balanced solution that combines both laying productivity and improved animal welfare. Further research should be performed to improve acceptance and appropriate use of resources by birds in an aviary system.