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Gaseous emissions from weaned pigs raised on different floor systems
Agriculture, Ecosystems and Environment 130 (2009) 86–92
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Gaseous emissions from weaned pigs raised on different floor systems Jean-Franc¸ois Cabaraux a,*, Franc¸ois-Xavier Philippe a, Martine Laitat b, Bernard Canart a, Marc Vandenheede a, Baudouin Nicks a a b
Veterinary Ecology and Ethology Unit, Department of Animal Production, Baˆt. B43, Faculty of Veterinary Medicine, University of Lie`ge, Boulevard de Colonster 20, 4000 Lie`ge, Belgium Department of Production Animals Clinic, Baˆt. B42, Faculty of Veterinary Medicine, University of Lie`ge, Boulevard de Colonster 20, 4000 Lie`ge, Belgium
A R T I C L E I N F O
A B S T R A C T
Article history: Received 28 March 2008 Received in revised form 24 November 2008 Accepted 26 November 2008 Available online 20 January 2009
Gaseous emissions from agriculture contribute to a number of environmental effects. Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are greenhouse gases taking part to the global problem of climate change. Ammonia (NH3) emissions are responsible of soil acidification and eutrophication and contribute also to indirect emissions of N2O. This work evaluated the influence of the type of floor on the emissions of these gases in the raising of weaned pigs. Two trials were carried out. In the first trial, the animals were kept either on fully slatted floor or on straw-based deep litter and, in the second one, either on fully slatted floor or on sawdust-based deep litter. For each trial and on each type of floor, 2 successive batches of weaned pigs were raised without changing the litter or emptying the slurry pit between the 2 batches. The rooms were automatically ventilated to maintain a constant ambient temperature. The performance of the animals was not significantly different according to the floor type. In trial 1, the nitrogen contents of the straw deep litter (including the substrate) and slurry were respectively 276 and 389 g pig1. In trial 2, the sawdust deep litter and slurry nitrogen contents were respectively 122 and 318 g pig1. Raising pigs on straw deep litter produced proportionately around 100% more NH3 than raising pigs on slatted floor (0.61 g NH3-N d1 pig1 vs. 0.31 g NH3-N d1 pig1; P < 0.05). Differences in CO2, H2O and CH4 emissions were not significant between systems. Raising pigs on sawdust deep litter produced also proportionately more NH3 (+52%; 0.55 g NH3-N d1 pig1 vs. 0.36 g NH3-N d1 pig1; P < 0.01) but also more CO2 (+25%; 427 g d1 pig1 vs. 341 g d1 pig1; P < 0.001) and H2O (+65%; 981 g d1 pig1 vs. 593 g d1 pig1; P < 0.001) and less CH4 (40%; 0.52 g d1 pig1 vs. 0.86 g d1 pig1; P < 0.001) than raising pigs on slatted floor. Practically no N2O emission was observed from rooms with slatted floor while the N2O emissions were 0.03 and 0.32 g N2O-N d1 pig1 for the straw and sawdust deep litter respectively. The warming potential of the greenhouse gases (N2O + CH4), were about 22, 34 and 168 g CO2 equivalents per day and per pig on fully slatted floor, straw or sawdust deep litter respectively. In conclusion, pollutant gas emissions from rearing of weaned pig seem lower with fully slatted plastic floor system than with deep litter systems. ß 2008 Elsevier B.V. All rights reserved.
Keywords: Weaned pigs Deep litter Slatted floor Ammonia Greenhouse gases Water vapour
1. Introduction Agriculture contributes importantly to pollutant gaseous emissions such as ammonia (NH3), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) (Monteny et al., 2006; Aneja et al., 2007). These gases have a number of environmental bad effects. NH3 contributes to the acidification and eutrophication of soils and waters (Brink et al., 2001) and to indirect emissions of N2O (Intergovernmental Panel on Climate Change, 2006a). Furthermore, NH3 is well known as a toxic gas, irritating the respiratory tract at concentrations exceeding 15 ppm (Urbain, 1997). In
* Corresponding author. Tel.: +32 4 366 59 03; fax: +32 4 366 41 22. E-mail address: [email protected] (J.-F. Cabaraux). 0167-8809/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2008.11.016
Europe, approximately 80% of NH3 production originated from animal production facilities (Brink et al., 2001). According to van der Peet-Schwering et al. (1999), approximately 50% of the ammonia emissions from pig production are from pig housing and slurry storage. The other 50% is emitted during surface application of the slurry. CO2, CH4 and N2O are the most important greenhouse gases (GHG) associated with livestock production. These gases take part to the global problem of climate change. However, agriculture is also a CO2-consumer through plant photosynthesis and the contribution of CO2 to the greenhouse effect is less important than that of CH4 and N2O, whose warming potentials over a 100year period are, respectively, 21 and 310 times that of CO2 (Intergovernmental Panel on Climate Change, 2007). N2O also contributes to the destruction of the ozone shield. Approximately
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40% and more than 50% of the anthropogenic emissions of CH4 and N2O originate from agriculture. Most important agriculture related CH4 sources are animals and their excreta (manure), whereas, most of the N2O is produced in the field (faeces and urine excreted during grazing, nitrogen (N) chemical fertilisers, land applied animal manure) and from animal houses where straw or litter is used (Monteny et al., 2006). The gaseous emissions from livestock houses are thus dependent among others from the housing and floor systems. The collection of wastes in the form of solid manure with litter presents various environmental advantages compared to liquid slurry such as a reduction in the weight of wastes collected, a decrease in the amount of N in the wastes and a decreased olfactory nuisance (Nicks et al., 2003, 2004). Furthermore, the use of straw has also the asset to improve the pig welfare (Tuyttens, 2005). However, the diminution of the N content of the wastes from litter results in the higher emissions of atmospheric N (N2), NH3 and N2O (Nicks et al., 2003, 2004). The Kyoto protocol specifies that each complying country should provide adequate methods and instruments to quantify, monitor and verify GHG emissions and their reductions (Monteny et al., 2006). It is thus important to know precisely the emissions associated with different production techniques. However, very few experiments have compared in standardized conditions gaseous emissions of weaned pigs according to floor systems and therefore, few data are available in the literature. The aim of this study was thus to quantify gaseous emissions in the raising of weaned pigs according to the type of floor (fully slatted floor, straw-based deep litter or sawdust-based deep litter). 2. Material and methods Two trials were carried out successively in experimental rooms located at the Faculty of Veterinary Medicine of Lie`ge University (Belgium). In the first trial, the gaseous emissions were measured with piglets kept either on fully slatted floor or on straw-based deep litter and in the second one, with piglets either on fully slatted floor or on sawdust-based deep litter. 2.1. Animals and feed For each trial and on each type of floor, 2 successive batches of 40 weaned pigs were raised without changing the litter or emptying the slurry pit between the 2 batches. All the pigs were originated from the same farrowing herd and were divided into 2 homogeneous groups according to the sex and the body weight. The pigs were fed ad libitum. Upon their arrival, they were given a transition feed (baby starter) which after 4 d was gradually replaced by a post-weaning feed (starter). Crude protein, lysine and crude fibre contents measured for the baby starter were 17.5, 1.3 and 3.9% and those for the starter, 17.6, 1.2 and 4.3% respectively. The pigs were weighted individually at the beginning and at the end of the experimental period. The quantities of feed ingested and water consumed were determined per batch. 2.2. Experimental rooms Two identical rooms with an area of 30 m2 and a volume of 103 m3 were arranged to house simultaneously a group of 40 weaned pigs on a fully slatted floor in the first one and on a deep litter in the second one. The slatted floor of plastic panels had a void percentage of 37%. The available floor area for the pigs was 12.2 m2 (0.31 m2 pig1). The slurry pit was 50 cm deep. Before the arrival of the first animals, 600 l water was poured into the pit to have a 5 cm water layer. The available floor space for animals in the room with deep litter was 21.6 m2 (0.54 m2 pig1). Straw deep
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litter was realized with a 30 cm layer before the arrival of the animals. Thereafter, supplementary quantities of straw were provided depending on the cleanliness of the litter. The total amount of wheat straw was 642 kg (8 kg pig1 on average for the 2 batches). For the sawdust deep litter, 2000 kg of sawdust was used to have a 20 cm layer before the arrivals of the pigs. No supplementary amount was provided thereafter, so the average amount for the 2 batches was 26.7 kg pig1. The sawdust had a dry matter (DM) content of 65% and was mostly composed of particles with a diameter of 0.2–2.0 mm, which represented 80% of the weight. At the end of each trial, slurry and deep litter were weighed and their DM content and N content, analysed by the Kjeldah method, were determined. About every 10 d, but not during the gaseous concentration measurements, wastes from the pigs raised on sawdust were dispersed over all the area of the pen and incorporated manually, which was not done with the strawbased litter. In addition, to avoid an excessively high concentration of dust in the air, the sawdust-based litter was moistened the 8th and the 13th days after the arrival of the second batch with respectively 24 and 48 l of water. Each room was ventilated with an exhaust fan and the ventilation rate was adapted automatically to maintain a constant ambient temperature. Fresh air entered through an opening of 0.34 m2 which was connected to the service corridor of the building; the outside air was thereby preheated before entering the experimental rooms. Moreover, a radiator and 2 heat lamps were placed in each room to obtain the piglets required temperature during the first part of the stay. The air temperatures of the 2 rooms and the corridor were measured automatically every hour. The ventilation rates were measured continuously and the hourly means were recorded with an Exavent apparatus (Fancom1) with accuracy as specified by the manufacturer, of 35 m3 h1, i.e. 1% of the maximum ventilation rate of the fan. 2.3. Gas emissions measurement The concentrations of gases in the 2 experimental rooms and the corridor supplying fresh air were measured with an apparatus from Innova Air Tech Instruments (1312 Photoacoustic Multi-gas Monitor) equipped and calibrated for the measurement of NH3, N2O, CH4, CO2 and water vapour (H2O). The air in the experimental rooms was sampled upstream of the exhaust fan and that of the corridor, at 1 m from the air inlet. For each batch, the concentrations were measured 3 times at about 1-week intervals and for 6 consecutive days respectively, i.e. during approximately 45% of the stay. The Multi-gas monitor was programmed by conducting a cycle of 3 measurements every half-hour, once every 10 min, the air being sampled successively in the room with the fully slated floor, the room with the deep litter and the corridor. The emissions were calculated on an hourly basis taking the hourly concentration as the average of the 2 measurements performed per hour at each location. The emissions were expressed in mg h1 utilizing the following formula: E = D (Ci Ce) with D, the hourly mass flow (kg air h1); Ci and Ce, the concentrations of gas in the air of the room and corridor respectively (mg kg1 dry air). The mean emissions per day and per pig were calculated for each series of measurements. 2.4. Statistical analyses Statistical analyses were realized for each trial separately. About performance, initial and final body weights and average daily gains data were collected individually and tested per trial according to the floor system using a general linear model -proc GLM- (SAS, 1999). About gaseous emissions, for each batch and each gas and for the combined data obtained with the 2 batches,
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the differences of the emissions with regard to the floor system were tested in the form of a mixed model for repeated measurements -proc mixed- (SAS, 1999). However, in each trial, because the litters were not changed and the slurry pit not emptied between the 2 batches, the second batch cannot be considered as a real replication of the first batch. 3. Results 3.1. Animal performance The performance is presented in Table 1. The staying duration of a batch was around 6 weeks. During trial 2, accidental losses occurred, respectively two in batch 1 and three in batch 2. In order to maintain equal the pig number in the 2 groups raised either on deep litter or on slatted floor, one healthy pig was removed from one of the experimental room the same day that one mortality was observed in the other room. The mean initial and final weights were respectively 7.14 0.2 and 23.0 1.6 kg (S.D. between 8 groups). The average daily weight gains (ADG) were not significantly different with pigs kept either on slatted floor or on deep litter, with an average of 382 17 g d1. The mean feed conversion ratio (kg feed kg1 gain) was 1.66 0.15. 3.2. Climatic characteristics of the rooms In trial 1, the average temperatures of the air were 23.9 8C in the room with the straw deep litter and 26.4 8C in the room with the slatted floor (Table 2). The mean ventilation rates were 216 and 238 m3 h1 for the 2 rooms respectively. In trial 2, the average temperatures of the air were 22.6 8C in the room with the sawdust deep litter and 24.2 8C in the room with the slatted floor. The mean ventilation rates were 414 and 483 m3 h1 for the 2 rooms respectively.
3.3. Amounts and composition of manure In trial 1, the amounts of straw manure and slurry removed at the end of the experiment were 27.5 kg pig1 at 326 g DM kg1 and 37.0 kg pig1 at 163 g DM kg1 respectively. For trial 2, there were 24.0 kg pig1 sawdust manure (438 g DM kg1) and 32.0 kg pig1 slurry (124 g DM kg1) removed. In trial 1, the deep litter and slurry N contents were 30.7 and 64.5 g kg1 DM respectively and in trial 2, 11.6 and 80.1 g kg1 DM. Taking into account the amounts of deep litter and slurry produced and their DM content, their N content per pig raised could be calculated and were 276 g pig1 for the straw deep litter and 389 g pig1 for slurry in trial 1 and 122 g pig1 for the sawdust deep litter and 318 g pig1 for slurry in trial 2. 3.4. Gas emissions Table 3 presents the mean emissions observed for each batch and Fig. 1 shows the evolution of the emissions from the beginning to the end for each post-weaning period. In trial 1, over the 2 post-weaning periods altogether, raising pigs on straw deep litter produced proportionately around 100% more NH3 (0.61 g NH3-N d1 pig1 vs. 0.31 g NH3-N d1 pig1; P < 0.05) than raising pigs on slatted floor. Differences between CO2, H2O and CH4 emissions were not significant. No N2O was measured from the slurry while the N2O emissions from the straw deep litter were observed only during the stay of the second batch (0.06 g N2O-N d1 pig1). Gas emissions increased regularly from the beginning to the end of each post-weaning period whatever the floor system (Fig. 1). In trial 2 and over the 2 periods altogether, raising pigs on sawdust deep litter produced also per day proportionately more NH3 (52%; 0.55 g NH3-N d1 vs. 0.36 g NH3-N d1; P < 0.01), CO2 (25%; 427 g d1 vs. 341 g d1; P < 0.001) and H2O (65%; 981 g d1 vs. 593 g d1; P < 0.001) and less CH4 (40%; 0.52 g d1 vs.
Table 1 Animal performance. Batch
Trial 1 Straw deep litter
Trial 2 Fully slatted floor
Sawdust deep litter
Fully slatted floor
Pigs number
1 2 1 and 2
40 40 80
40 40 80
38 37 75
38 37 75
Staying duration (d)
1 2 1 and 2
39 46 85
39 46 85
40 40 80
40 40 80
Initial weight (kg)
1 2 Mean S.D.
7.4a 1.1 7.0a 1.2 7.2a 1.2
Final weight (kg)
1 2 Mean S.D.
21.9a 2.7 25.5a 3.8 23.7a 3.3
Average daily gain (g d1)
1 2 Mean S.D.
Feed conversion ratio (kg feed kg1 gain)
1 2 Mean
Drinking water (l) per day
Drinking water (l) per kg ingested feed
373a 59 401a 72 387a 65
7.4a 1.0 7.0a 1.3 7.2a 1.2
7.0b 1.1 7.2b 1.1 7.1b 1.1
6.9b 0.9 7.2b 1.1 7.1b 1.0
21.7a 2.9 25.0a 3.6 23.4a 3.3
22.3b 2.4 22.1b 3.0 22.2b 2.7
21.5b 3.0 23.7b 3.6 22.6b 3.3
368a 62 391a 67 379a 64
381b 52 372b 74 377b 63
362b 66 410b 74 386b 70
1.37 1.76 1.57
1.66 1.81 1.74
1.51 1.77 1.64
1.64 1.73 1.69
1 2 Mean
1.6 1.6 1.6
1.6 1.3 1.5
1.7 1.8 1.8
1.3 1.7 1.5
1 2 Mean
3.1 2.3 2.7
2.6 1.9 2.3
3.0 2.7 2.9
2.2 2.4 2.3
Data within a trial and a line with different superscripts (a, b) are significantly different (P < 0.05).
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Table 2 Mean air temperatures of experimental rooms and service corridor, and mean ventilation rates during the 2 periods. Batch
Trial 1
Trial 2
Straw deep litter room
Fully slatted floor room
Service corridor
Sawdust deep litter room
Fully slatted floor room
Service corridor
(8C) 24.4 1.8 23.4 1.3 23.9 1.6
27.1 1.8 26.7 1.0 26.4 1.6
16.5 1.8 15.4 1.3 15.9 1.7
17.7 1.5 14.9 1.8 16.3 1.6
22.7 0.8 22.5 1.0 22.6 0.9
23.8 1.4 24.5 1.0 24.2 1.2
Ventilation rates (m3 h1) 1 229 80 2 203 60 Mean S.D. 216 71
253 87 224 89 238 88
421 158 407 59 414 109
454 219 511 71 483 145
Air temperatures 1 2 Mean S.D.
– – –
0.86 g d1; P < 0.001) than raising pigs on slatted floor. Practically no N2O emission was observed from the room with slatted floor (0.01 g N2O-N d1 pig1) while the N2O emissions were 0.08 and 0.57 g N2O-N d1 pig1 respectively for the first and the second batches on sawdust deep litter. CO2 and H2O emissions increased regularly from the beginning to the end of each period whatever the floor system. 4. Discussion In each trial, the manure N content was higher in the slurry system than in the two litter systems. These data confirmed previous results with weaned (Nicks et al., 2000) and fattening pigs (Philippe et al., 2007a). The mean NH3 emissions from the slatted floor rooms were similar in the 2 trials (around 0.33 g NH3-N d1 pig1). These emissions were lower than those in the 2 rooms with deep litter (around 0.58 g NH3-N d1 pig1), which can partially explain the higher N content in slurry manure. The results with pigs on litter are in agreement with data of Nicks et al. (2003) but NH3 emission from the slurry system was low compared to data from the literature. The reference values for determining the best available techniques to reduce NH3 emissions are 0.50–0.66 kg NH3-N per weaner place, i.e. 1.35–1.80 g NH3-N d1. Some techniques defined as best available can reduce this level by 60% (European Commission, 2003). The low NH3 emissions of slurry observed
– – –
in this study could be related to the presence of a water layer in the bottom of the slurry pit at the beginning of the experiment and to the use of a plastic floor which is generally cleaner than a concrete floor. Higher NH3 emissions with litter compared to slurry were ever observed in trials with fattening pigs (Philippe et al., 2007a). According to Andersson (1996) a combination of high temperature and high pH, both observed in litter, could explain this difference. However, other factors like feed management – especially protein and fibre levels – and interior conditions can influence the level of NH3 emissions from pig housing. N2O is produced during the nitrification and denitrification processes which normally convert NH3 into inert N2 gas. Nitrification requires aerobic conditions and denitrification requires anaerobic conditions (Monteny et al., 2006). Both conditions can be found in deep litter but not in slurry. However, emissions from manure on the floor can occur in pig houses with slatted floors. So, values of about 2–4% of excreted N were observed with concrete slatted floor system for fattening pigs (Kermarrec, 1999). According to our results there were no N2O emissions with the fully slatted floor probably in relation with the use of plastic floor which is generally cleaner than concrete floor. The emissions from deep litter were lower with straw compared with sawdust (0.03 g N2O-N d1 pig1 vs. 0.32 g N2O-N d1 pig1). This difference between straw and sawdust was already observed by Nicks
Table 3 Gas emissions in the raising of 2 batches of weaned pigs on deep litter with straw or sawdust or on fully slatted floor. Trial 1
Trial 2
Straw deep litter
Fully slatted floor
S.E.
Sig.
Batch 1 NH3 (g N d1 pig1) N2O (g N d1 pig1) CH4 (g d1 pig1) CO2 (g d1 pig1) H2O (g d1 pig1)
0.66 0.00 0.56 327 694
0.29 0.00 1.03 308 634
0.15 – 0.06 38.1 104
NS NS
Batch 2 NH3 (g N d1 pig1) N2O (g N d1 pig1) CH4 (g d1 pig1) CO2 (g d1 pig1) H2O (g d1 pig1)
0.57 0.06 0.95 340 685
0.34 0.00 0.79 298 556
Batches 1 and 2 NH3 (g N d1 pig1) N2O (g N d1 pig1) CH4 (g d1 pig1) CO2 (g d1 pig1) H2O (g d1 pig1)
0.61 0.03 0.75 334 689
0.31 0.00 0.91 303 595
S.E.: mean standard error; Sig.: significance; NS: not significant. * P < 0.05. ** P < 0.01. *** P < 0.001.
Fully slatted floor
S.E.
NS NS
0.55 0.08 0.43 425 889
0.29 0.01 0.75 314 528
0.04 0.05 0.02 11 57.8
0.15 0.03 0.09 28.6 99.8
NS NS NS NS NS
0.55 0.57 0.61 429 1074
0.44 0.00 0.96 367 659
0.07 0.06 0.01 7.65 26.4
NS
0.07 0.01 0.1 19.7 48.1
0.55 0.32 0.52 427 981
0.36 0.01 0.86 341 593
0.04 0.08 0.02 7.15 37
**
NS NS NS NS
*
*
Sawdust deep litter
Sig. *
NS ** * *
** ** * **
** *** *** ***
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Fig. 1. Gas emission (per day and per pig) during the raising of weaned pigs on fully slatted floor (open bars) and on deep litter (closed bars) with 3 series of measurements per batch at the beginning (B), middle (M) and end (E) of each period.
et al. (2003) with 2 batches of weaned pigs (0.11 g N2O-N d1 pig1 vs. 0.69 g N2O-N d1 pig1). It is probably the state of litter aeration that accounts for this difference, being higher in the sawdust-based litter compared to that with straw. Indeed, the
sawdust litter was aerated every 10 d, except during the measurements, in order to favour composting. Kermarrec (1999) has shown that the aeration of sawdust-based litter strongly stimulates the release of N2O. However, the N2O emissions might
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be underestimated due to the fact that they were not measured on the days of sawdust litter aeration. Indeed, in a short laboratory trial (15 d) with continuous measurements, Kermarrec (1999) observed more N2O emissions (+70%) when the sawdust litter was mixed, all other conditions being similar. From deep litters, the nitrification process leads to N2 emissions. To estimate these emissions, the N balance (difference between N input (ingested N + litter N content)/retained N/ excreted N) was calculated on a basis of N retention by pigs equal to 53.6% of N consumption, as reported by Dourmad et al. (1999) for weaned pigs with initial and final weight of 7.5 and 26 kg respectively. On this basis, N2 emissions from the straw and the sawdust deep litter systems were 1.68 and 4.22 g N2N d1 pig1respectively, representing 21 and 52% of excreted N. Applied to results from the slurry system, the N balance calculation led to a negative results (0.3 g N2-N d1 pig1 on average for the 2 trials) indicating a slight over-valuation either of retained N or/and excreted N. CH4 originates from enteric fermentation by animal and degradation of organic components in manure. CH4 from manure is produced under anaerobic conditions and is enhanced by high temperature (Sommer and Møller, 2000). The production by the pigs is related to the amount of gross energy intake of which about 0.6% is eliminated in that form (Schneider and Menke, 1982; Crutzen et al., 1986) and to the level of dietary fibre (Ramonet et al., 2000; Noblet and Le Goff, 2001). The low levels of CH4 emissions observed in these experiments (mean: 0.76 g d1) suggest that production from the 2 experimental rooms came essentially from the digestive tract of animals. These results with pigs on litter are in agreement with data of Nicks et al. (2003) who observed an average CH4 emission with 2 successive batches of weaned pigs raised either on a straw or on a sawdust deep litter of 0.91 and 0.48 g d1 pig1respectively. Results with pigs on slatted floor were however more lower than data from Groot Koerkamp and Uenk (1997) who reported a CH4 emission in commercial farms of 11 g d1 weaner1 kept on partially slatted floor. According to the authors, these values were however 3 times higher than expected according to previous measurements. The CO2 emissions are linked to animal metabolism and the relationship is about 688 g CO2 generated for each 100 W of energy produced by a pig per day (Bruce, 1981). For piglets of 15 kg (the mean weight in the present trials), the thermoneutral heat production is estimated at 66.2 W (Bruce, 1981; Baxter, 1984) and thus the CO2 production at 456 g d1. This value is still higher than the mean value observed in the present study (351 g d1). Pig CO2 production (PCO2 ) is however dependent of other factors than pig weight. It depends also of the animal respiratory quotient (RQ) defined as the volume of CO2 produced divided by the volume of O2 consumed. The lowest RQ, the lowest PCO2 . In weaned pigs, RQ ranges from 0.8 to 1.1 according to the level of feed intake and a RQ decrease from 1.1 to 0.8 decreases PCO2 by 22% (Van Ouwerkerk and Pedersen, 1994). Values of PCO2 observed in this study seem associated with low RQ values. Furthermore, concerning the effect of the floor type, manure fermentation is known to increase CO2 release (Van Ouwerkerk and Pedersen, 1994). Because these gaseous emissions according to the type of floor were different, the impact on environment will be also different. Indeed, the warming potential of the GHG, N2O and CH4 together, can be expressed in CO2 equivalents (CO2eq) using the following 1 equation: CO2 eq ðg d pig1 Þ ¼ 21ECH4 þ 310EN2 O , with ECH4 and EN2 O being the emissions of CH4 and N2O (g d1 pig1). For N2O, indirect emissions from atmospheric deposition of N from NH3 on soils and water surfaces have been added to the direct emissions. The indirect emissions were calculated considering an emission of 0.01 kg N2O-N kg1 emitted NH3-N (Intergovernmental Panel on Climate Change, 2006b). The CO2eq emissions were about 22, 34
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and 168 g d1 pig1 respectively on fully slatted floor, straw deep litter or sawdust deep litter. The difference between the groups was mainly due to the difference in N2O emissions. The production of H2O by animals depends both on their weight and the ambient temperature. The minimal production at 15 kg can be estimated to be 177 g H2O d1, with the maximum values being about 4 times higher (Baxter, 1984). The other sources of H2O emissions are those released from the manure and from animals playing with the drinker. The H2O emissions were in the mean similar in the rooms with slatted floor for the 2 trials (594 g d1 pig1) and were higher in the rooms with deep litter. These observations were previously reported by Philippe et al. (2007a,b) with fattening pigs. Higher H2O emissions with weaned piglets from sawdust deep litter rooms compared with straw deep litter rooms were also observed by Nicks et al. (2003). Water consumption was relatively similar between the two systems in trial 1 (6% or 100 ml d1 pig1 higher for animals on straw vs. slatted floor) but was 17% higher (or 300 ml d1 pig1) for the piglets on sawdust compared to those on slatted floor in trial 2. This could partially explain the difference. However, significantly greater H2O emissions in sawdust deep litter could also be explained by the higher temperature due to fermentation observed in this litter. As H2O emissions are higher with the deep litter system, this system needs higher ventilation rates in ‘‘winter conditions’’ when air relative humidity is the key factor determining the ventilation rate. CO2 and H2O emissions increased regularly from the beginning to the end of the stay of the pigs whatever the floor system. In both trials, these emissions were clearly lower at the beginning of the stay of the second batch than at the end of the stay of the first one, indicating the decisive influence of pig weight on the gaseous emissions. NH3 emissions from the deep litters show a similar evolution and the mean emission at the beginning of the stay of the second batch was, on average of the 2 trials, 78% lower than the emission at the end of the stay of the first batch. This difference was however lower, 24% on average, with pigs on slatted floor. NH3 emissions seem thus more dependent of the manure accumulation as slurry than as deep litter. Such a difference was not observed with CH4 emissions. 5. Conclusion Rearing pigs on deep litter (with straw or sawdust) has a good brand image for the consumer and, generally, a good welfare image for the public. However, raising weaned pigs on deep litter produced more NH3 than raising on slatted floor. With sawdust as litter, there were also more N2O and CO2 emissions but less CH4. According to the warming potentials of GHG gases (N2O and CH4), raising weaned pigs on deep litter, and mainly on sawdust-based deep litter, emitted also more CO2eq. On the other hand, the higher NH3 emissions induced lower N content in the litter compared to the slurry. In conclusion, the fully slatted plastic floor system is better than the deep litter system to limit NH3 and CO2eq emissions related to the raising of weaned pigs. Acknowledgment The research was supported by the Ministry of the Walloon Region of Belgium. References Andersson, M., 1996. Performance of bedding materials in affecting ammonia emissions from pig manure. J. Agric. Eng. Res. 65, 213–222. Aneja, V.P., Blunden, J., James, K., Schlesinger, W.H., Knighton, R., Gilliam, W., Niyogi, D., Cole, S., 2007. Ammonia assessment from agriculture: status and national
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needs. In: Monteny, G.-J., Hartung, E. (Eds.), Ammonia Emissions in Agriculture. Wageningen Academic Publishers, Wageningen, pp. 44–51. Baxter, S., 1984. Intensive pig production–environmental management and design. Granada publishing, London, United Kingdom. Brink, J.C., Kroeze, C., Klimont, Z., 2001. Ammonia abatement and its impact on emissions of nitrous oxide and methane. Part 1. Method. Atmos. Environ. 35, 6299–6312. Bruce, J.M., 1981. Ventilation and temperature control criteria for pigs. In: Clark, J.A. (Ed.), Environmental Aspects of Housing for Animal Production. Butterworths, London, United Kingdom, pp. 197–216. Crutzen, P.J., Aselmann, I., Seiler, W., 1986. Methane production by domestic animals, wild ruminants, other herbivorous fauna, and humans. Tellus B 38, 271–284. Dourmad, J.Y., Se`ve, B., Latimier, P., Boisen, S., Fernandez, J., van der Peet-Schwering, C., Jongbloed, A.W., 1999. Nitrogen consumption, utilisation and losses in pig production in France, The Netherlands and Denmark. Livest. Prod. Sci. 58, 261–264. European Commission, 2003. Integrated pollution prevention and control (IPPC). Reference document on best available techniques for intensive rearing of poultry and pigs. http://www.jrc.es/pub/english.cgi/0/733169 (date of access: October 3, 2008). Groot Koerkamp, P., Uenk, G., 1997. Climatic conditions and aerial pollutants in and emissions from commercial animal production systems in the Netherlands. In: Voermans, J.A.M., Monteny, G.J. (Eds.), Proceedings of the International Symposium Ammonia and Odour Control from Animal Production Facilities. Vinkeloord, The Netherlands p. 139. Intergovernmental Panel on Climate Change, 2006a. 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Vol. 1: General Guidance and Reporting. Prepared by the National Greenhouse Gas Inventories Programme. In: Eggleston, H.S., Buendia, L., Miwa, K., Ngara, T., Tanabe, K. (Eds.), Institute for Global Environmental Strategies, Hayama, Japan. Intergovernmental Panel on Climate Change, 2006b. 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Vol. 4: Agriculture, Forestry and Other Land Use. Prepared by the National Greenhouse Gas Inventories Programme. In: Eggleston, H.S., Buendia, L., Miwa, K., Ngara, T., Tanabe, K. (Eds.), Institute for Global Environmental Strategies, Hayama, Japan. Intergovernmental Panel on Climate Change, 2007. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. In: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M., Miller, H.L. (Eds.), Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Kermarrec, C., 1999. Bilan et transformations de l’azote en e´levage intensif de porcs sur litie`re. Ph.D. Thesis, Universite´ de Rennes 1, France.
Monteny, G.J., Bannink, A., Chadwick, D., 2006. Greenhouse gas abatement strategies for animal husbandry. Agric. Ecosyst. Environ. 112, 163–170. Nicks, B., Laitat, M., Vandenheede, M., De´siron, A., Canart, B., 2000. Water vapour emission and nitrogen balance from a sawdust deep litter system for weaned pigs. Ann. Zootech. 49, 119–128. Nicks, B., Laitat, M., Vandenheede, M., De´siron, A., Verhaeghe, C., Canart, B., 2003. Emissions of ammonia, nitrous oxide, methane, carbon dioxide and water vapour in the raising of weaned pigs on straw-based and sawdust-based deep litters. Anim. Res. 52, 299–308. Nicks, B., Laitat, M., Farnir, F., Vandenheede, M., De´siron, A., Verhaeghe, C., Canart, B., 2004. Gaseous emissions from deep-litter pens with straw or sawdust for fattening pigs. Anim. Sci. 78, 99–107. Noblet, J., Le Goff, G., 2001. Effect of dietary fibre on the energy value of feeds for pigs. Anim. Feed Sci. Technol. 90, 35–52. Philippe, F.X., Laitat, M., Canart, B., Vandenheede, M., Nicks, B., 2007a. Comparison of ammonia and greenhouse gas emissions during the fattening of pigs, kept either on fully slatted floor or on deep litter. Livest. Sci. 111, 144–152. Philippe, F.X., Laitat, M., Canart, B., Vandenheede, M., Nicks, B., 2007b. Gaseous emissions during the fattening of pigs kept either on fully slatted floors or on straw flow. Animal 1, 1515–1523. Ramonet, Y., van Milgen, J., Dourmad, J.Y., Dubois, S., Meunier-Salaun, M.C., Noblet, J., 2000. The effect of dietary fibre on energy utilisation and partitioning of heat production over pregnancy in sows. Br. J. Nutr. 84, 85–94. SAS, 1999. SAS/STAT User’s Guide: Statistics (Version 8). SAS Inst. Inc., Cary, North Caroline, USA. Schneider, W., Menke, K.H., 1982. Untersuchungen u¨ber den energetischen Futterwert von Melasseschnitzeln in Rationen fu¨r Schweine. Z. Tierphysiol. Tierernaehr. Futtermittelk. 48, 233–240. Sommer, S.G., Møller, H.B., 2000. Emission of greenhouse gases during composting of deep litter from pig production—effect of straw content. J. Agric. Sci. 134, 327–335. Tuyttens, F.A.M., 2005. The importance of straw for pig and cattle welfare: a review. Appl. Anim. Behav. Sci. 92, 261–282. Urbain, B., 1997. Toxicite´ de l’ammoniac pour l’appareil respiratoire du porc. Ph.D. Thesis, University of Lie`ge, Belgium. van der Peet-Schwering, C.M.C., Aarnink, A.J.A., Rom, H.B., Dourmad, J.Y., 1999. Ammonia emissions from pig houses in The Netherlands, Denmark and France. Livest. Prod. Sci. 58, 265–269. Van Ouwerkerk, E.N.J., Pedersen, S., 1994. Application of the carbon dioxide mass balance method to evaluate ventilation rates in livestock buildings. In: Proceedings of the XII CIGR World Congress on Agricultural Engineering, vol. 1, Milano, Italy, pp. 516–529.
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Agriculture, Ecosystems and Environment journal homepage: www.elsevier.com/locate/agee
Gaseous emissions from weaned pigs raised on different floor systems Jean-Franc¸ois Cabaraux a,*, Franc¸ois-Xavier Philippe a, Martine Laitat b, Bernard Canart a, Marc Vandenheede a, Baudouin Nicks a a b
Veterinary Ecology and Ethology Unit, Department of Animal Production, Baˆt. B43, Faculty of Veterinary Medicine, University of Lie`ge, Boulevard de Colonster 20, 4000 Lie`ge, Belgium Department of Production Animals Clinic, Baˆt. B42, Faculty of Veterinary Medicine, University of Lie`ge, Boulevard de Colonster 20, 4000 Lie`ge, Belgium
A R T I C L E I N F O
A B S T R A C T
Article history: Received 28 March 2008 Received in revised form 24 November 2008 Accepted 26 November 2008 Available online 20 January 2009
Gaseous emissions from agriculture contribute to a number of environmental effects. Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are greenhouse gases taking part to the global problem of climate change. Ammonia (NH3) emissions are responsible of soil acidification and eutrophication and contribute also to indirect emissions of N2O. This work evaluated the influence of the type of floor on the emissions of these gases in the raising of weaned pigs. Two trials were carried out. In the first trial, the animals were kept either on fully slatted floor or on straw-based deep litter and, in the second one, either on fully slatted floor or on sawdust-based deep litter. For each trial and on each type of floor, 2 successive batches of weaned pigs were raised without changing the litter or emptying the slurry pit between the 2 batches. The rooms were automatically ventilated to maintain a constant ambient temperature. The performance of the animals was not significantly different according to the floor type. In trial 1, the nitrogen contents of the straw deep litter (including the substrate) and slurry were respectively 276 and 389 g pig1. In trial 2, the sawdust deep litter and slurry nitrogen contents were respectively 122 and 318 g pig1. Raising pigs on straw deep litter produced proportionately around 100% more NH3 than raising pigs on slatted floor (0.61 g NH3-N d1 pig1 vs. 0.31 g NH3-N d1 pig1; P < 0.05). Differences in CO2, H2O and CH4 emissions were not significant between systems. Raising pigs on sawdust deep litter produced also proportionately more NH3 (+52%; 0.55 g NH3-N d1 pig1 vs. 0.36 g NH3-N d1 pig1; P < 0.01) but also more CO2 (+25%; 427 g d1 pig1 vs. 341 g d1 pig1; P < 0.001) and H2O (+65%; 981 g d1 pig1 vs. 593 g d1 pig1; P < 0.001) and less CH4 (40%; 0.52 g d1 pig1 vs. 0.86 g d1 pig1; P < 0.001) than raising pigs on slatted floor. Practically no N2O emission was observed from rooms with slatted floor while the N2O emissions were 0.03 and 0.32 g N2O-N d1 pig1 for the straw and sawdust deep litter respectively. The warming potential of the greenhouse gases (N2O + CH4), were about 22, 34 and 168 g CO2 equivalents per day and per pig on fully slatted floor, straw or sawdust deep litter respectively. In conclusion, pollutant gas emissions from rearing of weaned pig seem lower with fully slatted plastic floor system than with deep litter systems. ß 2008 Elsevier B.V. All rights reserved.
Keywords: Weaned pigs Deep litter Slatted floor Ammonia Greenhouse gases Water vapour
1. Introduction Agriculture contributes importantly to pollutant gaseous emissions such as ammonia (NH3), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) (Monteny et al., 2006; Aneja et al., 2007). These gases have a number of environmental bad effects. NH3 contributes to the acidification and eutrophication of soils and waters (Brink et al., 2001) and to indirect emissions of N2O (Intergovernmental Panel on Climate Change, 2006a). Furthermore, NH3 is well known as a toxic gas, irritating the respiratory tract at concentrations exceeding 15 ppm (Urbain, 1997). In
* Corresponding author. Tel.: +32 4 366 59 03; fax: +32 4 366 41 22. E-mail address: [email protected] (J.-F. Cabaraux). 0167-8809/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2008.11.016
Europe, approximately 80% of NH3 production originated from animal production facilities (Brink et al., 2001). According to van der Peet-Schwering et al. (1999), approximately 50% of the ammonia emissions from pig production are from pig housing and slurry storage. The other 50% is emitted during surface application of the slurry. CO2, CH4 and N2O are the most important greenhouse gases (GHG) associated with livestock production. These gases take part to the global problem of climate change. However, agriculture is also a CO2-consumer through plant photosynthesis and the contribution of CO2 to the greenhouse effect is less important than that of CH4 and N2O, whose warming potentials over a 100year period are, respectively, 21 and 310 times that of CO2 (Intergovernmental Panel on Climate Change, 2007). N2O also contributes to the destruction of the ozone shield. Approximately
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40% and more than 50% of the anthropogenic emissions of CH4 and N2O originate from agriculture. Most important agriculture related CH4 sources are animals and their excreta (manure), whereas, most of the N2O is produced in the field (faeces and urine excreted during grazing, nitrogen (N) chemical fertilisers, land applied animal manure) and from animal houses where straw or litter is used (Monteny et al., 2006). The gaseous emissions from livestock houses are thus dependent among others from the housing and floor systems. The collection of wastes in the form of solid manure with litter presents various environmental advantages compared to liquid slurry such as a reduction in the weight of wastes collected, a decrease in the amount of N in the wastes and a decreased olfactory nuisance (Nicks et al., 2003, 2004). Furthermore, the use of straw has also the asset to improve the pig welfare (Tuyttens, 2005). However, the diminution of the N content of the wastes from litter results in the higher emissions of atmospheric N (N2), NH3 and N2O (Nicks et al., 2003, 2004). The Kyoto protocol specifies that each complying country should provide adequate methods and instruments to quantify, monitor and verify GHG emissions and their reductions (Monteny et al., 2006). It is thus important to know precisely the emissions associated with different production techniques. However, very few experiments have compared in standardized conditions gaseous emissions of weaned pigs according to floor systems and therefore, few data are available in the literature. The aim of this study was thus to quantify gaseous emissions in the raising of weaned pigs according to the type of floor (fully slatted floor, straw-based deep litter or sawdust-based deep litter). 2. Material and methods Two trials were carried out successively in experimental rooms located at the Faculty of Veterinary Medicine of Lie`ge University (Belgium). In the first trial, the gaseous emissions were measured with piglets kept either on fully slatted floor or on straw-based deep litter and in the second one, with piglets either on fully slatted floor or on sawdust-based deep litter. 2.1. Animals and feed For each trial and on each type of floor, 2 successive batches of 40 weaned pigs were raised without changing the litter or emptying the slurry pit between the 2 batches. All the pigs were originated from the same farrowing herd and were divided into 2 homogeneous groups according to the sex and the body weight. The pigs were fed ad libitum. Upon their arrival, they were given a transition feed (baby starter) which after 4 d was gradually replaced by a post-weaning feed (starter). Crude protein, lysine and crude fibre contents measured for the baby starter were 17.5, 1.3 and 3.9% and those for the starter, 17.6, 1.2 and 4.3% respectively. The pigs were weighted individually at the beginning and at the end of the experimental period. The quantities of feed ingested and water consumed were determined per batch. 2.2. Experimental rooms Two identical rooms with an area of 30 m2 and a volume of 103 m3 were arranged to house simultaneously a group of 40 weaned pigs on a fully slatted floor in the first one and on a deep litter in the second one. The slatted floor of plastic panels had a void percentage of 37%. The available floor area for the pigs was 12.2 m2 (0.31 m2 pig1). The slurry pit was 50 cm deep. Before the arrival of the first animals, 600 l water was poured into the pit to have a 5 cm water layer. The available floor space for animals in the room with deep litter was 21.6 m2 (0.54 m2 pig1). Straw deep
87
litter was realized with a 30 cm layer before the arrival of the animals. Thereafter, supplementary quantities of straw were provided depending on the cleanliness of the litter. The total amount of wheat straw was 642 kg (8 kg pig1 on average for the 2 batches). For the sawdust deep litter, 2000 kg of sawdust was used to have a 20 cm layer before the arrivals of the pigs. No supplementary amount was provided thereafter, so the average amount for the 2 batches was 26.7 kg pig1. The sawdust had a dry matter (DM) content of 65% and was mostly composed of particles with a diameter of 0.2–2.0 mm, which represented 80% of the weight. At the end of each trial, slurry and deep litter were weighed and their DM content and N content, analysed by the Kjeldah method, were determined. About every 10 d, but not during the gaseous concentration measurements, wastes from the pigs raised on sawdust were dispersed over all the area of the pen and incorporated manually, which was not done with the strawbased litter. In addition, to avoid an excessively high concentration of dust in the air, the sawdust-based litter was moistened the 8th and the 13th days after the arrival of the second batch with respectively 24 and 48 l of water. Each room was ventilated with an exhaust fan and the ventilation rate was adapted automatically to maintain a constant ambient temperature. Fresh air entered through an opening of 0.34 m2 which was connected to the service corridor of the building; the outside air was thereby preheated before entering the experimental rooms. Moreover, a radiator and 2 heat lamps were placed in each room to obtain the piglets required temperature during the first part of the stay. The air temperatures of the 2 rooms and the corridor were measured automatically every hour. The ventilation rates were measured continuously and the hourly means were recorded with an Exavent apparatus (Fancom1) with accuracy as specified by the manufacturer, of 35 m3 h1, i.e. 1% of the maximum ventilation rate of the fan. 2.3. Gas emissions measurement The concentrations of gases in the 2 experimental rooms and the corridor supplying fresh air were measured with an apparatus from Innova Air Tech Instruments (1312 Photoacoustic Multi-gas Monitor) equipped and calibrated for the measurement of NH3, N2O, CH4, CO2 and water vapour (H2O). The air in the experimental rooms was sampled upstream of the exhaust fan and that of the corridor, at 1 m from the air inlet. For each batch, the concentrations were measured 3 times at about 1-week intervals and for 6 consecutive days respectively, i.e. during approximately 45% of the stay. The Multi-gas monitor was programmed by conducting a cycle of 3 measurements every half-hour, once every 10 min, the air being sampled successively in the room with the fully slated floor, the room with the deep litter and the corridor. The emissions were calculated on an hourly basis taking the hourly concentration as the average of the 2 measurements performed per hour at each location. The emissions were expressed in mg h1 utilizing the following formula: E = D (Ci Ce) with D, the hourly mass flow (kg air h1); Ci and Ce, the concentrations of gas in the air of the room and corridor respectively (mg kg1 dry air). The mean emissions per day and per pig were calculated for each series of measurements. 2.4. Statistical analyses Statistical analyses were realized for each trial separately. About performance, initial and final body weights and average daily gains data were collected individually and tested per trial according to the floor system using a general linear model -proc GLM- (SAS, 1999). About gaseous emissions, for each batch and each gas and for the combined data obtained with the 2 batches,
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the differences of the emissions with regard to the floor system were tested in the form of a mixed model for repeated measurements -proc mixed- (SAS, 1999). However, in each trial, because the litters were not changed and the slurry pit not emptied between the 2 batches, the second batch cannot be considered as a real replication of the first batch. 3. Results 3.1. Animal performance The performance is presented in Table 1. The staying duration of a batch was around 6 weeks. During trial 2, accidental losses occurred, respectively two in batch 1 and three in batch 2. In order to maintain equal the pig number in the 2 groups raised either on deep litter or on slatted floor, one healthy pig was removed from one of the experimental room the same day that one mortality was observed in the other room. The mean initial and final weights were respectively 7.14 0.2 and 23.0 1.6 kg (S.D. between 8 groups). The average daily weight gains (ADG) were not significantly different with pigs kept either on slatted floor or on deep litter, with an average of 382 17 g d1. The mean feed conversion ratio (kg feed kg1 gain) was 1.66 0.15. 3.2. Climatic characteristics of the rooms In trial 1, the average temperatures of the air were 23.9 8C in the room with the straw deep litter and 26.4 8C in the room with the slatted floor (Table 2). The mean ventilation rates were 216 and 238 m3 h1 for the 2 rooms respectively. In trial 2, the average temperatures of the air were 22.6 8C in the room with the sawdust deep litter and 24.2 8C in the room with the slatted floor. The mean ventilation rates were 414 and 483 m3 h1 for the 2 rooms respectively.
3.3. Amounts and composition of manure In trial 1, the amounts of straw manure and slurry removed at the end of the experiment were 27.5 kg pig1 at 326 g DM kg1 and 37.0 kg pig1 at 163 g DM kg1 respectively. For trial 2, there were 24.0 kg pig1 sawdust manure (438 g DM kg1) and 32.0 kg pig1 slurry (124 g DM kg1) removed. In trial 1, the deep litter and slurry N contents were 30.7 and 64.5 g kg1 DM respectively and in trial 2, 11.6 and 80.1 g kg1 DM. Taking into account the amounts of deep litter and slurry produced and their DM content, their N content per pig raised could be calculated and were 276 g pig1 for the straw deep litter and 389 g pig1 for slurry in trial 1 and 122 g pig1 for the sawdust deep litter and 318 g pig1 for slurry in trial 2. 3.4. Gas emissions Table 3 presents the mean emissions observed for each batch and Fig. 1 shows the evolution of the emissions from the beginning to the end for each post-weaning period. In trial 1, over the 2 post-weaning periods altogether, raising pigs on straw deep litter produced proportionately around 100% more NH3 (0.61 g NH3-N d1 pig1 vs. 0.31 g NH3-N d1 pig1; P < 0.05) than raising pigs on slatted floor. Differences between CO2, H2O and CH4 emissions were not significant. No N2O was measured from the slurry while the N2O emissions from the straw deep litter were observed only during the stay of the second batch (0.06 g N2O-N d1 pig1). Gas emissions increased regularly from the beginning to the end of each post-weaning period whatever the floor system (Fig. 1). In trial 2 and over the 2 periods altogether, raising pigs on sawdust deep litter produced also per day proportionately more NH3 (52%; 0.55 g NH3-N d1 vs. 0.36 g NH3-N d1; P < 0.01), CO2 (25%; 427 g d1 vs. 341 g d1; P < 0.001) and H2O (65%; 981 g d1 vs. 593 g d1; P < 0.001) and less CH4 (40%; 0.52 g d1 vs.
Table 1 Animal performance. Batch
Trial 1 Straw deep litter
Trial 2 Fully slatted floor
Sawdust deep litter
Fully slatted floor
Pigs number
1 2 1 and 2
40 40 80
40 40 80
38 37 75
38 37 75
Staying duration (d)
1 2 1 and 2
39 46 85
39 46 85
40 40 80
40 40 80
Initial weight (kg)
1 2 Mean S.D.
7.4a 1.1 7.0a 1.2 7.2a 1.2
Final weight (kg)
1 2 Mean S.D.
21.9a 2.7 25.5a 3.8 23.7a 3.3
Average daily gain (g d1)
1 2 Mean S.D.
Feed conversion ratio (kg feed kg1 gain)
1 2 Mean
Drinking water (l) per day
Drinking water (l) per kg ingested feed
373a 59 401a 72 387a 65
7.4a 1.0 7.0a 1.3 7.2a 1.2
7.0b 1.1 7.2b 1.1 7.1b 1.1
6.9b 0.9 7.2b 1.1 7.1b 1.0
21.7a 2.9 25.0a 3.6 23.4a 3.3
22.3b 2.4 22.1b 3.0 22.2b 2.7
21.5b 3.0 23.7b 3.6 22.6b 3.3
368a 62 391a 67 379a 64
381b 52 372b 74 377b 63
362b 66 410b 74 386b 70
1.37 1.76 1.57
1.66 1.81 1.74
1.51 1.77 1.64
1.64 1.73 1.69
1 2 Mean
1.6 1.6 1.6
1.6 1.3 1.5
1.7 1.8 1.8
1.3 1.7 1.5
1 2 Mean
3.1 2.3 2.7
2.6 1.9 2.3
3.0 2.7 2.9
2.2 2.4 2.3
Data within a trial and a line with different superscripts (a, b) are significantly different (P < 0.05).
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Table 2 Mean air temperatures of experimental rooms and service corridor, and mean ventilation rates during the 2 periods. Batch
Trial 1
Trial 2
Straw deep litter room
Fully slatted floor room
Service corridor
Sawdust deep litter room
Fully slatted floor room
Service corridor
(8C) 24.4 1.8 23.4 1.3 23.9 1.6
27.1 1.8 26.7 1.0 26.4 1.6
16.5 1.8 15.4 1.3 15.9 1.7
17.7 1.5 14.9 1.8 16.3 1.6
22.7 0.8 22.5 1.0 22.6 0.9
23.8 1.4 24.5 1.0 24.2 1.2
Ventilation rates (m3 h1) 1 229 80 2 203 60 Mean S.D. 216 71
253 87 224 89 238 88
421 158 407 59 414 109
454 219 511 71 483 145
Air temperatures 1 2 Mean S.D.
– – –
0.86 g d1; P < 0.001) than raising pigs on slatted floor. Practically no N2O emission was observed from the room with slatted floor (0.01 g N2O-N d1 pig1) while the N2O emissions were 0.08 and 0.57 g N2O-N d1 pig1 respectively for the first and the second batches on sawdust deep litter. CO2 and H2O emissions increased regularly from the beginning to the end of each period whatever the floor system. 4. Discussion In each trial, the manure N content was higher in the slurry system than in the two litter systems. These data confirmed previous results with weaned (Nicks et al., 2000) and fattening pigs (Philippe et al., 2007a). The mean NH3 emissions from the slatted floor rooms were similar in the 2 trials (around 0.33 g NH3-N d1 pig1). These emissions were lower than those in the 2 rooms with deep litter (around 0.58 g NH3-N d1 pig1), which can partially explain the higher N content in slurry manure. The results with pigs on litter are in agreement with data of Nicks et al. (2003) but NH3 emission from the slurry system was low compared to data from the literature. The reference values for determining the best available techniques to reduce NH3 emissions are 0.50–0.66 kg NH3-N per weaner place, i.e. 1.35–1.80 g NH3-N d1. Some techniques defined as best available can reduce this level by 60% (European Commission, 2003). The low NH3 emissions of slurry observed
– – –
in this study could be related to the presence of a water layer in the bottom of the slurry pit at the beginning of the experiment and to the use of a plastic floor which is generally cleaner than a concrete floor. Higher NH3 emissions with litter compared to slurry were ever observed in trials with fattening pigs (Philippe et al., 2007a). According to Andersson (1996) a combination of high temperature and high pH, both observed in litter, could explain this difference. However, other factors like feed management – especially protein and fibre levels – and interior conditions can influence the level of NH3 emissions from pig housing. N2O is produced during the nitrification and denitrification processes which normally convert NH3 into inert N2 gas. Nitrification requires aerobic conditions and denitrification requires anaerobic conditions (Monteny et al., 2006). Both conditions can be found in deep litter but not in slurry. However, emissions from manure on the floor can occur in pig houses with slatted floors. So, values of about 2–4% of excreted N were observed with concrete slatted floor system for fattening pigs (Kermarrec, 1999). According to our results there were no N2O emissions with the fully slatted floor probably in relation with the use of plastic floor which is generally cleaner than concrete floor. The emissions from deep litter were lower with straw compared with sawdust (0.03 g N2O-N d1 pig1 vs. 0.32 g N2O-N d1 pig1). This difference between straw and sawdust was already observed by Nicks
Table 3 Gas emissions in the raising of 2 batches of weaned pigs on deep litter with straw or sawdust or on fully slatted floor. Trial 1
Trial 2
Straw deep litter
Fully slatted floor
S.E.
Sig.
Batch 1 NH3 (g N d1 pig1) N2O (g N d1 pig1) CH4 (g d1 pig1) CO2 (g d1 pig1) H2O (g d1 pig1)
0.66 0.00 0.56 327 694
0.29 0.00 1.03 308 634
0.15 – 0.06 38.1 104
NS NS
Batch 2 NH3 (g N d1 pig1) N2O (g N d1 pig1) CH4 (g d1 pig1) CO2 (g d1 pig1) H2O (g d1 pig1)
0.57 0.06 0.95 340 685
0.34 0.00 0.79 298 556
Batches 1 and 2 NH3 (g N d1 pig1) N2O (g N d1 pig1) CH4 (g d1 pig1) CO2 (g d1 pig1) H2O (g d1 pig1)
0.61 0.03 0.75 334 689
0.31 0.00 0.91 303 595
S.E.: mean standard error; Sig.: significance; NS: not significant. * P < 0.05. ** P < 0.01. *** P < 0.001.
Fully slatted floor
S.E.
NS NS
0.55 0.08 0.43 425 889
0.29 0.01 0.75 314 528
0.04 0.05 0.02 11 57.8
0.15 0.03 0.09 28.6 99.8
NS NS NS NS NS
0.55 0.57 0.61 429 1074
0.44 0.00 0.96 367 659
0.07 0.06 0.01 7.65 26.4
NS
0.07 0.01 0.1 19.7 48.1
0.55 0.32 0.52 427 981
0.36 0.01 0.86 341 593
0.04 0.08 0.02 7.15 37
**
NS NS NS NS
*
*
Sawdust deep litter
Sig. *
NS ** * *
** ** * **
** *** *** ***
90
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Fig. 1. Gas emission (per day and per pig) during the raising of weaned pigs on fully slatted floor (open bars) and on deep litter (closed bars) with 3 series of measurements per batch at the beginning (B), middle (M) and end (E) of each period.
et al. (2003) with 2 batches of weaned pigs (0.11 g N2O-N d1 pig1 vs. 0.69 g N2O-N d1 pig1). It is probably the state of litter aeration that accounts for this difference, being higher in the sawdust-based litter compared to that with straw. Indeed, the
sawdust litter was aerated every 10 d, except during the measurements, in order to favour composting. Kermarrec (1999) has shown that the aeration of sawdust-based litter strongly stimulates the release of N2O. However, the N2O emissions might
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be underestimated due to the fact that they were not measured on the days of sawdust litter aeration. Indeed, in a short laboratory trial (15 d) with continuous measurements, Kermarrec (1999) observed more N2O emissions (+70%) when the sawdust litter was mixed, all other conditions being similar. From deep litters, the nitrification process leads to N2 emissions. To estimate these emissions, the N balance (difference between N input (ingested N + litter N content)/retained N/ excreted N) was calculated on a basis of N retention by pigs equal to 53.6% of N consumption, as reported by Dourmad et al. (1999) for weaned pigs with initial and final weight of 7.5 and 26 kg respectively. On this basis, N2 emissions from the straw and the sawdust deep litter systems were 1.68 and 4.22 g N2N d1 pig1respectively, representing 21 and 52% of excreted N. Applied to results from the slurry system, the N balance calculation led to a negative results (0.3 g N2-N d1 pig1 on average for the 2 trials) indicating a slight over-valuation either of retained N or/and excreted N. CH4 originates from enteric fermentation by animal and degradation of organic components in manure. CH4 from manure is produced under anaerobic conditions and is enhanced by high temperature (Sommer and Møller, 2000). The production by the pigs is related to the amount of gross energy intake of which about 0.6% is eliminated in that form (Schneider and Menke, 1982; Crutzen et al., 1986) and to the level of dietary fibre (Ramonet et al., 2000; Noblet and Le Goff, 2001). The low levels of CH4 emissions observed in these experiments (mean: 0.76 g d1) suggest that production from the 2 experimental rooms came essentially from the digestive tract of animals. These results with pigs on litter are in agreement with data of Nicks et al. (2003) who observed an average CH4 emission with 2 successive batches of weaned pigs raised either on a straw or on a sawdust deep litter of 0.91 and 0.48 g d1 pig1respectively. Results with pigs on slatted floor were however more lower than data from Groot Koerkamp and Uenk (1997) who reported a CH4 emission in commercial farms of 11 g d1 weaner1 kept on partially slatted floor. According to the authors, these values were however 3 times higher than expected according to previous measurements. The CO2 emissions are linked to animal metabolism and the relationship is about 688 g CO2 generated for each 100 W of energy produced by a pig per day (Bruce, 1981). For piglets of 15 kg (the mean weight in the present trials), the thermoneutral heat production is estimated at 66.2 W (Bruce, 1981; Baxter, 1984) and thus the CO2 production at 456 g d1. This value is still higher than the mean value observed in the present study (351 g d1). Pig CO2 production (PCO2 ) is however dependent of other factors than pig weight. It depends also of the animal respiratory quotient (RQ) defined as the volume of CO2 produced divided by the volume of O2 consumed. The lowest RQ, the lowest PCO2 . In weaned pigs, RQ ranges from 0.8 to 1.1 according to the level of feed intake and a RQ decrease from 1.1 to 0.8 decreases PCO2 by 22% (Van Ouwerkerk and Pedersen, 1994). Values of PCO2 observed in this study seem associated with low RQ values. Furthermore, concerning the effect of the floor type, manure fermentation is known to increase CO2 release (Van Ouwerkerk and Pedersen, 1994). Because these gaseous emissions according to the type of floor were different, the impact on environment will be also different. Indeed, the warming potential of the GHG, N2O and CH4 together, can be expressed in CO2 equivalents (CO2eq) using the following 1 equation: CO2 eq ðg d pig1 Þ ¼ 21ECH4 þ 310EN2 O , with ECH4 and EN2 O being the emissions of CH4 and N2O (g d1 pig1). For N2O, indirect emissions from atmospheric deposition of N from NH3 on soils and water surfaces have been added to the direct emissions. The indirect emissions were calculated considering an emission of 0.01 kg N2O-N kg1 emitted NH3-N (Intergovernmental Panel on Climate Change, 2006b). The CO2eq emissions were about 22, 34
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and 168 g d1 pig1 respectively on fully slatted floor, straw deep litter or sawdust deep litter. The difference between the groups was mainly due to the difference in N2O emissions. The production of H2O by animals depends both on their weight and the ambient temperature. The minimal production at 15 kg can be estimated to be 177 g H2O d1, with the maximum values being about 4 times higher (Baxter, 1984). The other sources of H2O emissions are those released from the manure and from animals playing with the drinker. The H2O emissions were in the mean similar in the rooms with slatted floor for the 2 trials (594 g d1 pig1) and were higher in the rooms with deep litter. These observations were previously reported by Philippe et al. (2007a,b) with fattening pigs. Higher H2O emissions with weaned piglets from sawdust deep litter rooms compared with straw deep litter rooms were also observed by Nicks et al. (2003). Water consumption was relatively similar between the two systems in trial 1 (6% or 100 ml d1 pig1 higher for animals on straw vs. slatted floor) but was 17% higher (or 300 ml d1 pig1) for the piglets on sawdust compared to those on slatted floor in trial 2. This could partially explain the difference. However, significantly greater H2O emissions in sawdust deep litter could also be explained by the higher temperature due to fermentation observed in this litter. As H2O emissions are higher with the deep litter system, this system needs higher ventilation rates in ‘‘winter conditions’’ when air relative humidity is the key factor determining the ventilation rate. CO2 and H2O emissions increased regularly from the beginning to the end of the stay of the pigs whatever the floor system. In both trials, these emissions were clearly lower at the beginning of the stay of the second batch than at the end of the stay of the first one, indicating the decisive influence of pig weight on the gaseous emissions. NH3 emissions from the deep litters show a similar evolution and the mean emission at the beginning of the stay of the second batch was, on average of the 2 trials, 78% lower than the emission at the end of the stay of the first batch. This difference was however lower, 24% on average, with pigs on slatted floor. NH3 emissions seem thus more dependent of the manure accumulation as slurry than as deep litter. Such a difference was not observed with CH4 emissions. 5. Conclusion Rearing pigs on deep litter (with straw or sawdust) has a good brand image for the consumer and, generally, a good welfare image for the public. However, raising weaned pigs on deep litter produced more NH3 than raising on slatted floor. With sawdust as litter, there were also more N2O and CO2 emissions but less CH4. According to the warming potentials of GHG gases (N2O and CH4), raising weaned pigs on deep litter, and mainly on sawdust-based deep litter, emitted also more CO2eq. On the other hand, the higher NH3 emissions induced lower N content in the litter compared to the slurry. In conclusion, the fully slatted plastic floor system is better than the deep litter system to limit NH3 and CO2eq emissions related to the raising of weaned pigs. Acknowledgment The research was supported by the Ministry of the Walloon Region of Belgium. References Andersson, M., 1996. Performance of bedding materials in affecting ammonia emissions from pig manure. J. Agric. Eng. Res. 65, 213–222. Aneja, V.P., Blunden, J., James, K., Schlesinger, W.H., Knighton, R., Gilliam, W., Niyogi, D., Cole, S., 2007. Ammonia assessment from agriculture: status and national
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needs. In: Monteny, G.-J., Hartung, E. (Eds.), Ammonia Emissions in Agriculture. Wageningen Academic Publishers, Wageningen, pp. 44–51. Baxter, S., 1984. Intensive pig production–environmental management and design. Granada publishing, London, United Kingdom. Brink, J.C., Kroeze, C., Klimont, Z., 2001. Ammonia abatement and its impact on emissions of nitrous oxide and methane. Part 1. Method. Atmos. Environ. 35, 6299–6312. Bruce, J.M., 1981. Ventilation and temperature control criteria for pigs. In: Clark, J.A. (Ed.), Environmental Aspects of Housing for Animal Production. Butterworths, London, United Kingdom, pp. 197–216. Crutzen, P.J., Aselmann, I., Seiler, W., 1986. Methane production by domestic animals, wild ruminants, other herbivorous fauna, and humans. Tellus B 38, 271–284. Dourmad, J.Y., Se`ve, B., Latimier, P., Boisen, S., Fernandez, J., van der Peet-Schwering, C., Jongbloed, A.W., 1999. Nitrogen consumption, utilisation and losses in pig production in France, The Netherlands and Denmark. Livest. Prod. Sci. 58, 261–264. European Commission, 2003. Integrated pollution prevention and control (IPPC). Reference document on best available techniques for intensive rearing of poultry and pigs. http://www.jrc.es/pub/english.cgi/0/733169 (date of access: October 3, 2008). Groot Koerkamp, P., Uenk, G., 1997. Climatic conditions and aerial pollutants in and emissions from commercial animal production systems in the Netherlands. In: Voermans, J.A.M., Monteny, G.J. (Eds.), Proceedings of the International Symposium Ammonia and Odour Control from Animal Production Facilities. Vinkeloord, The Netherlands p. 139. Intergovernmental Panel on Climate Change, 2006a. 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Vol. 1: General Guidance and Reporting. Prepared by the National Greenhouse Gas Inventories Programme. In: Eggleston, H.S., Buendia, L., Miwa, K., Ngara, T., Tanabe, K. (Eds.), Institute for Global Environmental Strategies, Hayama, Japan. Intergovernmental Panel on Climate Change, 2006b. 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Vol. 4: Agriculture, Forestry and Other Land Use. Prepared by the National Greenhouse Gas Inventories Programme. In: Eggleston, H.S., Buendia, L., Miwa, K., Ngara, T., Tanabe, K. (Eds.), Institute for Global Environmental Strategies, Hayama, Japan. Intergovernmental Panel on Climate Change, 2007. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. In: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M., Miller, H.L. (Eds.), Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Kermarrec, C., 1999. Bilan et transformations de l’azote en e´levage intensif de porcs sur litie`re. Ph.D. Thesis, Universite´ de Rennes 1, France.
Monteny, G.J., Bannink, A., Chadwick, D., 2006. Greenhouse gas abatement strategies for animal husbandry. Agric. Ecosyst. Environ. 112, 163–170. Nicks, B., Laitat, M., Vandenheede, M., De´siron, A., Canart, B., 2000. Water vapour emission and nitrogen balance from a sawdust deep litter system for weaned pigs. Ann. Zootech. 49, 119–128. Nicks, B., Laitat, M., Vandenheede, M., De´siron, A., Verhaeghe, C., Canart, B., 2003. Emissions of ammonia, nitrous oxide, methane, carbon dioxide and water vapour in the raising of weaned pigs on straw-based and sawdust-based deep litters. Anim. Res. 52, 299–308. Nicks, B., Laitat, M., Farnir, F., Vandenheede, M., De´siron, A., Verhaeghe, C., Canart, B., 2004. Gaseous emissions from deep-litter pens with straw or sawdust for fattening pigs. Anim. Sci. 78, 99–107. Noblet, J., Le Goff, G., 2001. Effect of dietary fibre on the energy value of feeds for pigs. Anim. Feed Sci. Technol. 90, 35–52. Philippe, F.X., Laitat, M., Canart, B., Vandenheede, M., Nicks, B., 2007a. Comparison of ammonia and greenhouse gas emissions during the fattening of pigs, kept either on fully slatted floor or on deep litter. Livest. Sci. 111, 144–152. Philippe, F.X., Laitat, M., Canart, B., Vandenheede, M., Nicks, B., 2007b. Gaseous emissions during the fattening of pigs kept either on fully slatted floors or on straw flow. Animal 1, 1515–1523. Ramonet, Y., van Milgen, J., Dourmad, J.Y., Dubois, S., Meunier-Salaun, M.C., Noblet, J., 2000. The effect of dietary fibre on energy utilisation and partitioning of heat production over pregnancy in sows. Br. J. Nutr. 84, 85–94. SAS, 1999. SAS/STAT User’s Guide: Statistics (Version 8). SAS Inst. Inc., Cary, North Caroline, USA. Schneider, W., Menke, K.H., 1982. Untersuchungen u¨ber den energetischen Futterwert von Melasseschnitzeln in Rationen fu¨r Schweine. Z. Tierphysiol. Tierernaehr. Futtermittelk. 48, 233–240. Sommer, S.G., Møller, H.B., 2000. Emission of greenhouse gases during composting of deep litter from pig production—effect of straw content. J. Agric. Sci. 134, 327–335. Tuyttens, F.A.M., 2005. The importance of straw for pig and cattle welfare: a review. Appl. Anim. Behav. Sci. 92, 261–282. Urbain, B., 1997. Toxicite´ de l’ammoniac pour l’appareil respiratoire du porc. Ph.D. Thesis, University of Lie`ge, Belgium. van der Peet-Schwering, C.M.C., Aarnink, A.J.A., Rom, H.B., Dourmad, J.Y., 1999. Ammonia emissions from pig houses in The Netherlands, Denmark and France. Livest. Prod. Sci. 58, 265–269. Van Ouwerkerk, E.N.J., Pedersen, S., 1994. Application of the carbon dioxide mass balance method to evaluate ventilation rates in livestock buildings. In: Proceedings of the XII CIGR World Congress on Agricultural Engineering, vol. 1, Milano, Italy, pp. 516–529.