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Influence of in-house composting of reused litter onlitter quality, ammonia volatilisation and incidenceof broiler foot pad dermatitisR.S. Martinsa, M.J. Hötzela & R. Polettoa

a Laboratório de Etologia Aplicada e Bem-Estar Animal, Departamento de Zootecniae Desenvolvimento Rural, Universidade Federal de Santa Catarina, Rodovia AdmarGonzaga, 1346, Itacorubi, Florianópolis, SC, 88034–001, BrazilAccepted author version posted online: 02 Sep 2013.Published online: 08 Jan 2014.

To cite this article: R.S. Martins, M.J. Hötzel & R. Poletto (2013) Influence of in-house composting of reused litter onlitter quality, ammonia volatilisation and incidence of broiler foot pad dermatitis, British Poultry Science, 54:6, 669-676,DOI: 10.1080/00071668.2013.838747

To link to this article: http://dx.doi.org/10.1080/00071668.2013.838747

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Influence of in-house composting of reused litter on litter quality, ammoniavolatilisation and incidence of broiler foot pad dermatitisR.S. MARTINS, M.J. HÖTZEL AND R. POLETTO*

Laboratório de Etologia Aplicada e Bem-Estar Animal, Departamento de Zootecnia e Desenvolvimento Rural,Universidade Federal de Santa Catarina, Rodovia Admar Gonzaga, 1346, Itacorubi, Florianópolis, SC, 88034–001,Brazil

Abstract 1. The objectives of this study were to evaluate the residual effects of two windrow compostingmethods for reused litter on its quality (pH, moisture, ammonia), ammonia (NH3) volatilisation and theprevalence (scores 0–4) of foot pad dermatitis (FPD) and hock burn (HB) on d 1, 7, 14 and 21 of age inbroilers. Litter was allowed to compost for 8 d within a 14-d interval between flocks.2. The composting methods studied were with or without a PVC plastic sheet. The same procedures wereapplied for three consecutive flocks, with litter initially having been used for 12 flocks. Data were analysedwith a mixed model of repeated measures of day, with main effects and interactions of day, compostingmethod, litter age (block) and house nested within method.3. At d 1, litter NH3 and NH3 volatilisation were higher in the covered litter method. Litter moistureincreased to 45.3% as broilers aged. The incidence of FPD also increased with age. No signs of HB werefound in any bird throughout the trials.4. There was no effect of litter composting methods on the prevalence of FPD or body weight at any age.5. Litter moisture should be controlled to avoid NH3 volatilisation reaching critical levels. Windrowcomposting of litter with a PVC plastic sheet may not be required when considering the broiler housingenvironment.

INTRODUCTION

The use of the same litter to raise multiple flocksis widely employed in countries such as Brazil andthe United States (Thaxton et al., 2003; Nagarajet al., 2007; Roll et al., 2011), which are majorbroiler producers and exporters (USDA/FAS,2012). To make this practice viable, it is importantto compost the reused litter between flocks. In-house composting of reused broiler litter betweenflocks is an effective way to reduce or eliminatepathogens (Lavergne et al., 2006; Macklin et al.,2006). However, the practice of rearing birds onreused litter may also increase the potential forthe development of foot pad dermatitis (FPD)(Macklin et al., 2008). This results from the low

litter quality, mainly due to high concentrations ofammonia (NH3) and elevated moisture content(Berg, 2004; Bilgili et al., 2009; Shepherd andFairchild, 2010).

FPD, also known as contact dermatitis, is aninflammation characterised by necrotic lesions inthe plantar surface of the foot pads and toes ofbroilers and turkeys (Greene et al., 1985;Shepherd and Fairchild, 2010). Development ofFPD is observed in broilers as young as 7 d of ageand lesions may become more severe as broilersget older or they may heal if litter conditions areimproved (Martland, 1985; Hashimoto et al.,2011). Hock burns (HBs) and breast blisters canalso be referred to as contact dermatitis, as theyresult from similar conditions that predispose

Correspondence to: R.S. Martins, Laboratório de Etologia Aplicada e Bem-Estar Animal, Departamento de Zootecnia e Desenvolvimento Rural,Universidade Federal de Santa Catarina, Rodovia Admar Gonzaga, 1346, Itacorubi, Florianópolis, SC, 88034–001, Brazil. E-mail: rsmartins00@yahoo.com.br

*Current address for R. Poletto is Instituto Federal do Rio Grande do Sul (IFRS), Rodovia RS 135, km 25, Distrito Engenheiro Luiz Englert, Sertão, RS,99170–000, Brazil

Accepted for publication 27 June 2013.

British Poultry Science, 2013Vol. 54, No. 6, 669–676, http://dx.doi.org/10.1080/00071668.2013.838747

© 2013 British Poultry Science Ltd

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birds to FPD (Greene et al., 1985; Martland, 1985;Shepherd and Fairchild, 2010). In addition tobeing an indicator of litter quality and manage-ment, more recently, the incidence and preva-lence of FPD have been adopted as indicators ofbroiler welfare (Algers and Berg, 2001). Severeconditions of FPD may cause pain and impairbirds’ walking ability, thus making their access tofeed and water resources more difficult(Martland, 1985; Bilgili et al., 2009).

In-house composting is performed by pilingup the litter into windrows down the length of thebroiler house, where it should be allowed to com-post for a minimum of 7 d (Lavergne et al., 2006;Macklin et al., 2006). The use of a PVC plasticsheet to cover the windrows is an alternativemethod adopted by the Brazilian broiler industry(Silva et al., 2007) and aims to concentrate NH3 inlitter for its sterilising effect against micro-organ-isms (Macklin et al., 2006) and undesirable insects(Silva et al., 2007). Nevertheless, when using thecovered method, NH3 in the litter may beretained for longer, thus further increasingNH3volatilisation and the development of FPD inthe next production cycle.

Thus, we hypothesised that windrow compost-ing of reused broiler litter with a PVC plasticsheet, compared to the usual method of compost-ing litter without cover, would lead to higher con-centrations of NH3 in the litter and thus in theatmosphere, promoting the development of FPDand HB. Also, body weight gain could be nega-tively affected by higher concentrations of NH3

(Miles et al., 2004). Therefore, the objectives ofthe current study were to evaluate the residualeffects of two methods of windrow compostingfor reused broiler litter on litter quality (pH,moisture, NH3), NH3 volatilisation and in theincidence of FPD and HB during the first threeweeks of age in broiler chickens.

The main purpose of the three-week record-ing period was to verify residual effects of thelitter composting process on the developmentof FPD, rather than to assess FPD progressionduring the complete rearing cycle. In theauthors’ understanding, extending the FPD andlitter evaluation period for longer than threeweeks would concur with occurrence of uncon-trolled factors that could mask or confoundresults of the composting treatments. This justifi-cation is especially relevant because FPD inci-dence is affected by many factors related tolitter quality maintenance, which becomes moredifficult as broilers grow, and as free space formovement in the house decreases. Another rea-son to record FPD in the initial three weeks onlywas that these first weeks may be the most criticalfor the development of FPD, mainly due tohigher sensibility of the feet, as there is less epi-dermis at this young age.

MATERIALS AND METHODS

Experimental design

This study was approved by the UniversidadeFederal de Santa Catarina’s Animal CareCommittee, protocol number PP00779. Theexperiment was carried out in a commercialfarm from February to August 2012, using 4 com-mercial broiler houses in Southern Brazil, near toSanta Catarina’s capital, Florianópolis city (lati-tude ~ 27°36′57.77”S, longitude ~ 48°32′29.21”O). This region has a subtropical climatecharacterised by hot, humid summers and gener-ally mild to cool winters. All broiler houses(1200 m2 each) were equipped with a positivepressure system for ventilation, automatic feeders(ratio of 1:50 birds) and nipple drinkers (ratio of1:25 birds). Birds were reared under similar envir-onmental conditions and uniform litter manage-ment practices.

For the study, d-old female chicks from acommercial strain of broilers (Cobb-500) werehoused at a stocking density of 11.25 birds/m2

(or 30.37 kg/m2) and were fed on a commercialdiet to meet the minimum nutritional require-ments described in the Brazilian Tables of AvianNutrition (Rostagno et al., 2011). Birds weremanually harvested and slaughtered at an averageof 47 d of age; all pre-slaughter and slaughterprocedures strictly followed the current Brazilianlegislation (BRASIL, 2000).

Broiler houses had concrete flooring beddedwith a mixture of reused material composed ofwood shavings and rice husks. The litter had adepth of approximately 25 cm and had beenreused for 11 flocks prior to the start of the study.

Experimental treatments

On the day after broiler harvesting, the com-pacted, high-moisture sublayer of litter (cake)was removed throughout each house and theremaining litter was piled into windrows in thecentre of the house, the piles measuring approxi-mately 100 m × 1.15 m × 4 m (Figure 1). A 14-dinterval between flocks was used, when litter wascomposted for 8 d.

The two methods of windrow in-house com-posting of broiler litter used in the study were (a)uncovered litter, and (b) covered litter with a PVCplastic sheet 150 microns thick, as shown inFigures 1a and 1b. After composting, the litterwas spread throughout each house, which wasventilated for 5 to 6 d prior to the placement ofthe chicks. A total volume of 15 m3 of new litterwas top-dressed on the old litter in each new flock.

In each block representing litter age, the 4experimental houses were split into two houses(replicates) per litter composting method and all

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experimental procedures were repeated for threesuccessive flocks (litter with 12, 13 and 14 flocks).This experimental design yielded 6 replicates pertreatment, as illustrated in Figure 2.

Litter sampling and measurements

Litter sampling, NH3 gas measurement and FPDand HB assessments were performed on d 1 (pla-cement of chicks), 7, 14 and 21. The proceduresdescribed below were carried out following thesame methodology in all houses and for all threereplications of the study. For analysis of pH, moist-ure and NH3 in the litter, samples were collectedthroughout each house at 18 points, in a zigzagpattern at the whole depth of the litter, frombottom to top through approximately 25 cm(Goan and Walker, 2000), thereby collectinghomogenous samples. This sampling proceduremethod was relevant because, as a part of the littermanagement practices during the growing period,litter was de-caked and mixed uniformly at leastonce a week. Samples were stored in zip-lock plas-tic bags at 4°C, and analysed within 24 h.

Determination of pH

For the determination of litter pH, 10 g of eachsample was dissolved into 50 ml of distilled waterand mixed intermittently for 30 minutes (Tedescoet al., 1995). The pH readings were taken using adigital pH meter previously calibrated (DM-22,Digimed, Piracicaba, São Paulo, Brazil).

Moisture content

Litter moisture content (%) was determined byweighing 20 g of each litter sample and placing itin an oven set at 65°C for 48 h (Tedesco et al.,1995). Samples were reweighed following the dry-ing process in order to determine the moisturecontent.

Ammonia released from broiler litter

The amount of NH3 released by the broiler littersamples was determined by micro diffusion(Hernandes and Cazetta, 2001). This method con-sisted of placing fresh broiler litter samples(100 g) into a glass container (500 cm3), whereanother flask (50 cm3) containing 10 cm3 of boricacid (H3BO3) solution 2% (w/v) was added ontop of the litter sample. After incubation for 18 hat 30°C, boric acid was titrated with a sulphuricacid solution (H2SO4) at 0.05 N, and to it wasadded a mixture of methyl red 0.2% (w/v) withbromocresol green 0.1% (w/v). NH3 releasedfrom litter (mg/100g) was converted into ppm/100g according to the following equation:

NH3 ¼ Vt � N � 17� 10

where NH3 is the amount of NH3 (ppm) releasedin 100 g of fresh litter sample; Vt is the volume ofsulphuric acid spent in titration (ml); N is thenormality of sulphuric acid, 0.05N; 17 is themolar mass of NH3 and 10 is the conversion coef-ficient from mg to ppm.

Figure 1. In-house windrow composting of reused litter for 8 . (A) Uncovered litter (B) covered litter with PVC plastic sheet (150 micronthick). Reused litter was composted for 8 d with no addition of water.

Figure 2. Scheme of the experimental design. (a) Houses with litter composted with the addition of a PVC plastic sheet and (b) houses withlitter composted without addition of a PVC plastic sheet.

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Litter management

Litter management (litter de-caking and mixing)during rearing of birds was performed at least oned prior to weekly samplings and bird evaluation. Ineach house, litter management was done with theaid of a garden rake and a de-caking litter machine(Agritech, Yanmar Tc 14, São Paulo, Brazil).

Ammonia volatilisation into the atmosphere

In each house, NH3 volatilisation (ppm) into theatmosphere was measured using a digital NH3

meter (DG-200, Instrutherm, Piracicaba, SaoPaulo, Brazil). The NH3 gas was sampled at 18points down the length of the houses: 6 pointsbetween the feeder and drinker lines, 6 pointsnear to drinkers and the last 6 points away fromdrinkers and feeders. All gas samplings wererecorded at the birds’ height between 11 am and 1pm The management of curtains and ventilationwas similar for all houses prior to and during datacollection.

Assessment of FPD and HB

In order to assess the incidence of FPD and HB,10 birds were gently picked up from 10 locationsin each house (n = 100). Birds were trapped forassessment in a circle made of a flexible woodenboard in two areas near to drinkers, two areasnear to feeders, three areas near the side walland three areas away from drinkers and feeders(resting area), according to the Welfare QualityAssessment Protocol for Poultry (WQAPP, 2009).

A scoring scale was used to assess the inci-dence of FPD and HB (WQAPP, 2009). In thescoring scale, 0 represented no evidence of FPDand HB, 1 and 2 represented minimum evidenceof FPD and HB and 3 and 4 represented evidenceof FPD and HB. Birds were also weighed andreleased immediately after FPD and HB evalua-tions. External and in-house temperatures wererecorded using a portable digital thermometer(C-02, Instrutherm, Piracicaba, São Paulo, Brazil)and relative humidity inside broiler houses wasmaintained between 50% to 70%, according totechnical recommendation.

Statistical analysis

The experiment was set in a block design withblocks determined by litter age, resulting in 6replications per treatment. Data analysis was per-formed using the Statistical Analysis System (SASSoftware Inst. Inc., Cary, NC, USA). All quantita-tive variables were assessed for normality. Dataanalyses were computed with a mixed model ana-lysis of variance (PROC MIXED) using repeatedmeasurements of day. The statistical modelincluded terms for the fixed effects of litter com-posting methods (treatments), broiler age or day,and block (litter age) and their interactions andhouse nested within treatment (as covariate).Mean differences were evaluated by Tukey’s posthoc test and results are shown as means ± SEM.Multiple linear regression analysis was carried outas an additional analysis to correlate the incidenceof FPD score 3 with litter parameters (moistureand NH3), broiler age and broiler body weight.For all statistical analyses, differences with P < 0.05were considered significant, while those withP < 0.1 were considered a trend towardssignificance.

RESULTS

Litter parameters according to windrowcomposting methods

Results on litter parameters respective to eachcomposting method are presented in Table 1.On d 7, litter pH in the covered method washigher compared to the uncovered compostingmethod (composting treatment × broiler age;P < 0.05). Concentrations of litter NH3 on d 1and 7 were also higher in the covered method(composting treatment × broiler age; P < 0.05),whereas litter moisture did not differ between thelitter composting methods studied at any time(litter composting treatment × broiler age;P > 0.05). In addition, no fixed effects of houseswere observed (P > 0.05).

Litter pH differed among the three blocks(block 1: 8.3; block 2: 8.5; and block 3:8.6 ± 0.02; P < 0.05). Litter moisture in blocks 2

Table 1. Litter pH, moisture content (%) and NH3 released from litter (ppm) in the uncovered and covered litter treatment in a three-weekgrowing period

Litter composting treatmentLitter

parameters d 1 d 7 d 14 d 21 SEM

Uncovered litter pH 8.49a 8.08a 8.54a 8.56a 0.03Moisture (%) 15.79a 20.81a 23.11a 27.76a 0.82Ammonia (ppm) 23.51b 11.94c 17.51b 19.27b 1.72

Covered litter pH 8.52a 8.29b 8.50a 8.59a 0.03Moisture (%) 16.25a 19.41a 23.45a 26.73a 0.82Ammonia (ppm) 35.43a 20.36b 16.84b 25.63b 1.72

a,b,cWithin a row, values not sharing a common superscript letter are significantly different P ≤ 0.(05).

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and 3 was greater than that in block 1 (block 1:17.1%; block 2: 23.1%; and block 3: 24.8% ± 0.7%;P < 0.05). The NH3 released from litter in block 3was higher compared with that of block 2 andblock 1 (block 1: 19.4; block 2: 18.3; and block 3:26.2 ± 1.2 ppm; P < 0.05).

Ammonia volatilisation to the atmosphere

The NH3 volatilisation into the atmosphere(ppm) for each litter composting method is pre-sented in Figure 3. On placement of chicks (d 1),the NH3 volatilisation in the uncovered litter com-posting method was almost twice as high as that inthe covered litter method (20.0 vs. 10.2 ± 1.3 ppm,respectively; litter composting treatment × broilerage; P < 0.05). NH3 volatilisation decreased by d 7,varying from 7 ppm to 13 ppm until the thirdweek of evaluation and no longer presented dif-ferences between litter composting methods (lit-ter composting treatment × broiler age; P > 0.05).NH3 volatilisation differed among all three blocks(block 1: 5.3; block 2: 17.1; and block 3:12.6 ± 0.8 ppm; P < 0.05). There was no evidenceof house effects (P > 0.05).

Incidence of FPD and HB

There was an increase in FPD prevalence from21% at 7 d of age to 55% at 21 d of age, whereasthe incidence of FPD scores 0 and 1 notablydecreased as broilers aged (day effect, P <0.05;Table 2). There was no statistical evidence thatthe composting methods tested in the currentstudy affected the prevalence of scores 0, 1, 2, 3or 4 of FPD in broilers at any age 7, 14 or 21 d)(litter composting treatment × broiler age;P > 0.05; Table 2). There was no evidence ofhouse or block effects on FPD prevalence(P > 0.05) and no signs of HB lesions werefound in any bird examined throughout theexperimental period.

Body weight gain and mortality

The litter composting methods did not influencebody weight gain (Figure 4) (litter compostingmethod × broiler age; P > 0.05). There was noevidence of house or block effects on weightgain (P > 0.05). Flock mortality rate during thefull rearing period (approximately 7 weeks) ran-ged between 4% and 6%.

Figure 3. Ammonia volatilszation (ppm) on d 1, 7, 14 and 21 into the houses where litter was composted with or without a PVC plasticsheet. Litter composting treatment× broiler age a,b P < 0.05.

Table 2. Incidence and score prevalence of foot pad dermatitis (FPD) on d 7, 14 and 21 in broilers reared on the uncovered or coveredlitter treatment

Broiler age (d)

FPD scoreLitter composting

treatment 7 14 21 SEM

0 uncovered 29.3% 17.5% 10.8% 3.6covered 38.8% 26.2% 11.8% 3.6

1 uncovered 21.3% 6.3% 5.3% 1.2covered 16.8% 7.8% 6.2% 1.2

2 uncovered 27.8% 23.7% 27.0% 2.5covered 23.7% 23.7% 28.0% 2.5

3 uncovered 21.3% 52.5% 56.2% 3.7covered 20.7% 42.2% 53.8% 3.7

4 uncovered 0.2% 0.0% 0.7% 0.1covered 0.0% 0.2% 0.2% 0.1

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External and in-house temperatures

External and in-house temperatures did not differbetween the litter composting methods during thethree-week growing period (litter compostingtreatment × broiler age; P > 0.05; Table 3).

External temperature differed among thethree blocks (block 1: 28.3°C; block 2: 20.3°C;and block 3: 22.01°C ± 0.1°C; P < 0.05), whereasin-house temperature did not differ among blocks(block 1: 28.0°C; block 2: 27.7°C; and block 3:27.6°C ± 0.1°C; P > 0.05). No fixed effects ofhouses were observed for the measurement of in-house temperature (P > 0.05).

Multiple linear regression for FPD score 3

There was a positive correlation between FPDscore 3 (evidence of FPD according to WQAPP,2009) with broiler age (r2 = 0.61; P < 0.01) andlitter moisture (r2 = 0.50; P < 0.01). There were nosignificant correlations between FPD score 3 andbroiler body weight or levels of litter NH3

(r2 = 0.005 e r2 = 0.17; P < 0.01, respectively).

DISCUSSION

In-house windrow composting of reused litter witha PVC plastic sheet resulted in higher concentra-tions of litter NH3 and thus higher NH3 volatilisa-tion at placement of the chicks. Wet litter (>35%)combined with alkaline pH promotes bacterialgrowth which decomposes uric acid, thereby

generating NH3 (Carey et al., 2004). However,even with the alkaline pH conditions, none ofthe experimental houses subjected to the coveredlitter composting method, a treatment thatretained more ammonia in the litter, exceededthe maximum NH3 reference concentrations of20 ppm (Council Directive, 2007). Therefore,these findings suggest that litter moisture below30%, as observed in the litters studied, may havecontributed to prevent higher NH3 emissions inthe broiler environment.

In the three-week growing period, the inci-dence of FPD did not differ between the two littercomposting methods, and the higher concentra-tions of litter NH3 released from the covered littermethod at week 1 (d 1 and d 7) did not increasethe occurrence or severity of FPD. The latter find-ing is in agreement with the results reported byNagaraj et al. (2007) and Youssef et al. (2011), whoalso reported no effects of litter NH3 alone in theaetiology of FPD in broilers and turkeys.According to the authors, other factors associatedwith litter quality and FPD aetiology should beinvestigated, apart from NH3.

In the current study, both litter moisture con-tent and the prevalence of score 3 FPD increased,showing a positive correlation and indicating thatlitter moisture may play a role in the onset of FPDlesions. These results corroborate previous studiesthat consider litter moisture as the leading factorfor development of FPD in broilers and turkeys(Greene et al., 1985; Martland, 1985; Youssef et al.,2011). In fact, litter moisture content greater than

Figure 4. Average weekly weight of broilers reared on uncovered or covered litter composting treatment. ns = non significant.

Table 3. External and house temperature (°C) in houses in which litter was composted with and without a PVC plastic tarp

Broiler age (d)

Temperature (°C)Litter composting

treatment 1 7 14 21 SEM

External temperature uncovered litter 23.7 24.3 23.0 23.3 0.202covered litter 24.2 24.4 22.7 23.0 0.202

House temperature uncovered litter 31.1 28.5 26.6 24.8 0.232covered litter 31.1 28.5 27.5 24.2 0.232

Litter composting treatment × broiler age: there was no effect of litter composting treatments on external and house temperatures, P > 0.05.

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30% has been strongly associated with a high pre-valence of FPD in broilers and turkeys, leading topoor animal welfare (Martland, 1985; Mayne et al.,2007; Youssef et al., 2010; Wu and Hocking, 2011).

The incidence of FPD in the current studywas very similar to that reported by Santos et al.(2002), who found an incidence of FPD rangingbetween 50% and 70% in a Brazilian flock at 20 dof age. Apart from litter moisture, another expla-nation for the high prevalence of FPD found inthe initial growing period may be the greateractivity of the birds at a young age. When birdsare more active, the contact of their feet with litteris more intense, which may increase the incidenceof FPD (de Jong et al., 2012). Further studiesshould be conducted in order to evaluate theprogression of HB and FPD lesions, in additionto air and litter quality parameters, until the timeof slaughter.

That fact that the incidence of FPD also had apositive correlation with broiler age may partiallysuggest that stocking density could be involved inthe development of the lesions (Buijs et al., 2009).Yet, the stocking density adopted in this study waswithin the broiler welfare protocols (EuropeanCommission, 2000) and by three weeks of age –which is when this study ended – it is still reasonablylow, as measured in kg/m2. According to Dawkinset al. (2004), the incidence of FPD is more likely tobe influenced by house environmental conditions,which may worsen as broilers grow, than by stockingdensity itself. Hence, it is also worth considering theeffect of time per se on FPD. Because it takes time forlesions to develop, they are likely to be more pre-valent during weeks two and three of the growingperiod compared with week one.

One hypotheses that may explain the absenceof HB is that they seem mostly to occur whenbroilers are older and heavier (Broom andReefmann, 2005; Hepworth et al., 2010).

Despite the fact that the experiment was car-ried out in Southern Brazil (subtropical climate –hot, humid summers and generally mild to coolwinters), during months that ranged from the endof summer (block 1), over autumn (block 2) tobeginning of winter (block 3), time of the yearhad no apparent effect on FPD incidence (veri-fied as a block effect). This outcome may be asso-ciated with frequency of litter mixing and cakeremoval and the effectiveness of ventilation inthe houses, essential practices employed to con-trol litter moisture and consequently NH3 emis-sion and development of FPD (Ritz et al., 2009).

In conclusion, the incidence of FPD in broilerchickens was not affected by the litter compostingmethods in a three-week growing period. Also, thehigher concentrations of NH3 released from thecovered litter method did not intensify the devel-opment of FPD. It is suggested that litter moisture

content should be controlled, preferably below30%, in order to limit NH3 volatilisation to harm-ful concentrations. The use of the litter compost-ing method with PVC plastic sheet may not berequired when considering the subsequent broilerhouse environment.

ACKNOWLEDGEMENTS

We thank the Graduate Program in Agroecossistemasof Universidade Federal de Santa Catarina, for finan-cial support. MJH was supported by CNPq (PQ308919/2009-2). Rosangela Poletto was supported byCAPES/Reuni. We are also grateful for the supportfrom the slaughterhouse and the broiler grower.

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