Systematic evaluation of in-house broiler litter windrowing effects on production benefits and environmental impact

Transcription

1 2014 Poultry Science Association, Inc. Systematic evaluation of in-house broiler litter windrowing effects on production benefits and environmental impact Y. Liang,* 1 J. B. Payne, C. Penn, G. T. Tabler, S. E. Watkins,# K. W. VanDevender,* and J. L. Purswell ǁ * Department of Biological and Agricultural Engineering, University of Arkansas, Fayetteville 72701; Department of Biosystems and Agricultural Engineering, and Department of Plant and Soil Sciences, Oklahoma State University, Stillwater 74074; Department of Poultry Science, Mississippi State University Extension Service, Starkville, MS 39762; # Center of Excellence for Poultry Science, University of Arkansas, Fayetteville 72701; and ǁ USDA Agricultural Research Service, Poultry Research Unit, Starkville, MS Primary Audience: Flock Supervisors, Researchers, Poultry Producers SUMMARY In-house windrowing of broiler litter between flocks has been adopted by producers to reduce pathogens and improve litter quality before chick placement. In this study, 5 consecutive windrow trials were conducted in commercial broiler houses for their effect on litter bacterial populations, organic matter stabilization, cumulative ammonia emissions, and nutrient transformation and compared with litter conditioning (tilling) in adjacent houses. No significant reduction of Clostridium spp. and Escherichia coli populations was found in windrowed litter from d 0 to 7. No significant difference of 7-d mortality was found between windrow and nonwindrow houses. The windrowed house resulted in better foot quality than the nonwindrowed house from 1 of 3 scored flocks. Water-soluble phosphorus increased in both windrowed and nonwindrowed litter; therefore, appreciable biotic and abiotic activity occurred in litter with both treatments after flocks were removed. Overall, no negative effect of windrow treatments on litter quality for agronomic applications was observed. Both the control and windrow treatments resulted in a decrease in litter moisture content (2 to 5%) likely beneficial to bird health conditions. High ammonia emissions persisted after windrow spreading; therefore, a need may exist for an extended period of ventilation or a litter amendment as crucial before chick placement. Litter amendment at a low dose was effective in lowering ammonia concentrations after windrowing and was more economical comparing to operating fans in winter conditions. Key words: broiler, windrowing, bacteria, litter, ammonia, temperature 2014 J. Appl. Poult. Res. 23 : Corresponding author: yliang@uark.edu

2 626 JAPR: Research Report DESCRIPTION OF PROBLEM In-house windrow composting of built-up broiler litter between flocks is being adopted in some production complexes in the United States. Although a typical composting process is known to stabilize organic materials, kill weed seeds, and reduce pathogens [1], the necessity to attain sufficiently high temperatures for an extended period is critical. The nature of modern litter management strategies and relatively short downtimes between flocks of broiler production creates challenges for successful adoption of windrowing as in-house composting. For example, producers best management practices in achieving drier litter during grow-out are in conflict with establishing a fast yet successful windrowing process, because most litter has a lower moisture content than what is required for optimal heating of the litter during windrow. It is uncertain under what litter condition water should be added, and if so, whether windrowing can eventually reduce the litter moisture content. Researchers [2] reported no difference in Clostridium populations recovered from litter windrow composted versus uncomposted when the litter was windrowed for 7 d without turning or adjustment of initial moisture content; however, they observed a significant reduction in Salmonella populations. Both aerobic and anaerobic bacterial counts were lower in composted than uncomposted litter before chick placement [3]. A decrease of anaerobic bacteria by windrow treatment on d 17 was found compared with nonwindrow treatment [4]. The increased temperatures created by windrowing litter can lead to increased ammonia volatilization during and following the windrowing process. Upon windrow disturbance (turning and respread), ammonia is often volatilized to the ambient environment, together with moisture vaporization. If not managed properly, unexpected high ammonia concentrations could sustain for extended periods after windrowing and negatively affect the subsequent flock. The dynamics of ammonia release as affected by air exchange (a result of building ventilation rate) is not well understood. The time or cost necessary to prepare the litter after in-house windrowing are not clearly defined. The objectives of the current study were (1) to determine the effect of litter windrowing or conditioning between broiler flocks on litter bacterial populations, and (2) to monitor and compare the organic matter stabilization, cumulative ammonia emission, and nutrient transformation from the litter windrowing and litter conditioning process. MATERIALS AND METHODS Broiler Houses and Windrow Experiments Field experiments were conducted at the University of Arkansas Division of Agriculture Applied Broiler Research Farm. The farm consists of 4 commercial broiler houses each measuring m ( ft). The farm operates under a standard broiler contract with a local integrator to raise chickens of 2.5 kg target weight. Each house had an initial placement of 21,040 chicks, with average growth periods of 48 d. Typical downtimes (periods between flocks when houses were empty) were 2 to 3 wk, except for a 12-week period from December 2011 to February All houses had a packed dirt floor underneath the bedding materials. New bedding material consisting of pine shavings was placed in all houses in March Five windrow trials were conducted on built-up litter (Table 1). Litter in windrowing houses was formed into windrows using a 75- hp tractor and a litter windrow blade [5]. These blades are commonly used on poultry farms due to their lower prices compared with other more expensive windrowing options. When used properly, the blade is capable of incorporating any compressed hardened litter (hard pan) into the windrow. Windrowing experiments were conducted in 2 houses (W_1 and W_2) for 7 to 13 d, with the other 2 houses using litter conditioning methods [6]. One of the 2 litter conditioning houses was used as a control house for obtaining litter nutrient and microbial samples. Caked litter was removed from the litter-conditioned houses between flocks with a tractor and commercial decaking machine [7], but not the windrowing houses. During the windrowing period, windrows were turned once to aerate the piles and allow for a more homogenous mixture. During windrow construction, turning, and respreading, 4- to m diameter exhaust fans were used

3 Liang et al.: BROILER LITTER WINDROWING 627 Table 1. Windrow trials conducted on built-up litter over 5 consecutive grow cycles Trial Windrow construction Windrow turning, d Windrow spreadout, d Flocks on same litter, n Sampled for microbial analysis 1 May 10, Jul. 10, Yes 3 Sep. 13, Nov. 22, Apr. 12, Yes to maintain an acceptable working condition inside the house. After windrow construction, 1 or 2 fan(s) were used continuously during monitoring. At least 7 d elapsed between the time of windrow spreading and new chick placement. For subsequent flocks after windrow trials, 7-d mortality rates were collected. Moisture content of litter in windrowing houses was determined 3 d before bird harvest to determine the needs of water addition for the windrow. Water was added to litter in 1 of the windrow houses (W_ 2) for trials 3, 4, and 5, but not trials 1 or 2. Approximately 3,500 L of water were uniformly added by an overhead sprinkler system (designed for other purposes) to the litter immediately before windrows were formed. Litter Mass Determination and Sampling Litter density and depth from the W_1 house were measured on the day of bird harvest to determine litter mass before in-house windrowing. Depth of litter was measured using a 10- cm diameter steel pipe of 0.5 m in length. One end of the pipe was sharpened to allow cutting through the litter down to the packed dirt floor. The exterior surface of the pipe was marked to allow reading of litter depth after its insertion. Depth measurements were made in 12 locations, 6 from the brood half and 6 from nonbrood half. Litter density was measured using a bucket. A 19-L polyvinyl chloride bucket was filled with litter to the top, gently dropped on the floor 3 times to allow settling, and refilled to the top again before weighing. The volume of the bucket was estimated by weighing the bucket filled with water to the brim. Litter density was determined by the recorded weight and volume of the bucket. Litter density from 12 locations in the brood and off-brood half was measured. Litter samples for nutrient analysis were taken from the W_1, W_2, and control houses pre- (time 0) and postwindrowing (time 1) or conditioning of all 5 trials. Time 0 samples were taken immediately after the first-pass conditioning for control, or immediately after windrows were constructed in the windrowing houses, whereas time 1 were taken the same day before spreading the windrows, except for trial 5. Litter samples from trial 5 were taken on d 7 for the purpose of being consistent with the sampling timing of microbial analysis for trial 2 (described herein). In each sampling event, 8 composite samples consisting of litter within a vertical portion were removed from the length of the pile. For microbial analysis, litter samples were taken from the W_1, W_2, and control houses at time 0 and time 1 of windrowing or conditioning after the second and fifth flocks on the same litter. Six composite litter samples were aseptically taken within established windrows in each house. Of the 6 windrow composite samples, 3 were collected from the internal of pile and 3 were collected from the pile surface. For the control house, 3 composite samples were aseptically collected following a zigzag pattern throughout the house. Composite samples consisted of 10 collection locations each weighing approximately 10 g. Each composite sample was pooled in a resealable bag, stored on ice, and transported to the University of Arkansas, Division of Agriculture, Veterinary Diagnostic Laboratory in Fayetteville for sample analysis. Upon arrival, samples were analyzed for Clostridium spp., Escherichia coli, and Staphylococcus aureus. Windrow Temperature Internal temperature of windrowed litter at 1 ft below the peak of the pile at 4 locations was measured with temperature sensors [8] and logged every 15 min using external data loggers [9]. Surface temperature of the pile at 2

4 628 JAPR: Research Report locations was measured with temperature sensors [10]. For the control, litter temperature at 4 locations about 5 cm under the litter surface throughout the house was recorded. Sample Analysis Moisture content was determined by differences in weight after air drying. Air-dried and ground poultry litter was analyzed for total nutrients (P, K, Mg, Ca, Na, Mn, Cl, Cu, Fe, Zn, and Mo [11]). Total C and N were analyzed on field samples with a Leco Truspec dry combustion analyzer [12]. Litter ph was determined with a ph probe at solid to solution ratio of 1:5 after an equilibration time of 45 min. Water-soluble P, Ca, Mg, K, and Na were extracted at 1:10 soil-todeionized water ratio, 1 h of reaction time, followed by filtration with a 0.45-µm filter before analysis by inductively coupled argon plasmaatomic emission spectroscopy. Results from the total digestions were used to calculate percent mass reduction (percent of initial litter mass that was degraded) based on the increase (relative to fresh litter) in concentration of nongaseous, easily recoverable, and plentiful elements P, Ca, and K. Clostridium spp. Upon arriving at the laboratory, 10 g of each composite sample were placed in a sterile 4.5-oz specimen container and 90 ml of sterile saline were added to create a 1:10 dilution of the initial sample. Each container was incubated in a shaking water bath at 75 C for 45 min. Each sample was serially diluted by pipetting 1 ml into 9-mL saline blanks. Using a 1-mL pipet, 0.1 ml of each diluted sample was spread plated onto blood agar [13] and incubated anaerobically at 37 C overnight. Following incubation, the plates were examined for growth and colonies were counted. One suspect colony was picked and streaked onto 2 blood agar plates. One plate was incubated aerobically and one plate was incubated anaerobically at 37 C overnight. Growth observed on both plates was interpreted as Clostridium spp. negative. E. coli. Ten grams of each composite sample were serially diluted in sterile saline as described above. Using a 1-mL pipet, 0.1 ml of each diluted sample was spread plated onto Maconkey agar [13] and incubated at 37 C for 24 h. Following incubation, the plates were examined for growth and colonies were counted. Staph. aureus. Ten grams of each composite sample were serially diluted in sterile saline as previously described. Using a 1-mL pipet, 0.1 ml of each diluted sample was spread plated onto Columbia CNA agar [13] and incubated at 37 C for 24 h. Following incubation, the plates were examined for growth and colonies were counted. Foot Scores Prior to harvest of flocks 4 and 5, 100 birds in the W_1 and control house were evaluated for foot scores. In flock 6, 100 birds per house were evaluated in all 4 houses for the flock to be sold. A wire catch pen was used to randomly confine approximately 30 to 40 birds in each quartile of the barn. Birds were randomly selected from the penned group and the feet (or bottom of the feet) were examined and scored [14] without inverting the birds. A 0 score indicated an unblemished foot with no visible burn or abrasion; a 1 score indicated a burn or abrasion approximately the size of a pencil eraser which had slight penetration into the tissue; a score of 2 indicated a larger burn that penetrated well into the tissue of the foot. All procedures were approved by the Animal Care and Use Committee at the University of Arkansas, Division of Agriculture, Agricultural Experiment Station. Ammonia Emission Monitoring Aerial emission monitoring started with the first flock on new bedding (March 2011), and ended at flock 6 (June 2012), covering 5 windrow trials and 6 grow-out cycles. The emission monitoring system consisted of the ammonia concentration monitoring instrument, a fan operation monitoring system, and a data acquisition and control system. All instruments were housed in an environmentally controlled trailer positioned in between the W_1 and W_2 houses. Ammonia concentrations were semicontinuously monitored from 3 selected locations in each house and an outside location using a photoacoustic analyzer [15]. One sampling was near a minimum ventilation sidewall exhaust fan in the brooding half of the house, the sec-

5 Liang et al.: BROILER LITTER WINDROWING 629 ond sampling was near another sidewall exhaust fan (nonbrooding area), and the third sampling location was near the center of the tunnel exhaust fan area of the house. The ambient air sample intake line was located under the eave above the cool cell inlets. Air sampling lines from the house sampling points to the instrument trailer were protected with insulation and temperature-controlled resistive heating cable to prevent in-line moisture condensation. Hourly sampling of concentrations was achieved by sequentially sampling 6 interior air sampling locations (each measured for 6.5 min) and the ambient air sample (measured for 20 min). When windrows were constructed, turned, or spread out in a house, concentrations at the exhaust were measured exclusively to allow calculation of emissions occurring throughout the duration of the event, typically lasting from 1 to 2 h. Data collection was interrupted twice during grow-out in 2011, due to a malfunction of the air conditioning unit of the instrumentation trailer in June and an instrument failure in August. This resulted in 2 incomplete emission measurements of grow-out cycles. Ventilation rates of the houses were calculated by fan capacities, calibrated in situ using Fan Assessment Numeration System, and duty cycles recorded by individual current switches installed on the fans. Analogue outputs from the current switches on 2-min intervals were recorded by an external data logger [16]. Measurement of the house static pressure differential was made with one static pressure sensor [17] in each house. Indoor and outdoor temperature and RH were measured with 2 and 1 transmitters [18], respectively. Analog outputs of static pressure and temperature and RH readings were recorded by the same external data logger. Emission Rate Calculation Ammonia emission rate was calculated by integrating the measured building ventilation rates and the net ammonia concentrations corrected to standard condition [19]. Statistical Analysis Paired t-tests were conducted between d 0 and 7 for each bacterium, nutrient, and for each windrow treatment [20]. Foot scores were analyzed using the GLM procedure of SAS by flock and by treatment, with birds as the replicate. RESULTS AND DISCUSSION Temperature and Moisture Windrow piles reached peak temperature in about 2 d (Figure 1). Peak internal temperature varied from 56 to 65 C, whereas the duration of internal temperature exceeding 55 C varied from 2 to 4 d in different trials (Table 2). Higher moisture content of litter in W_2 treatments resulted in higher peak temperature (Table 1). Windrow turning allowed release of heat and moisture. The second temperature rise after turning indicated rejuvenated microbial activity due to the aeration and mixing process. Peak surface temperature of windrow piles was between 29 and 43 C. Temperatures of nonwindrowed litter rose above ambient within 24 h of the first pass of litter conditioning, and remained elevated for 2 d before decreasing close to indoor air temperature (Figure 1). Litter characteristics before windrow construction (time 0) and after (time 1) are shown in Table 3. Litter moisture content determined at time 0 was low compared with values reported elsewhere [21]. This could be due to the sampling timing of the current study, in which litter samples were collected after windrow construction, or decaking and first-pass conditioning in the control house. A significant decrease in litter moisture content occurred in all treatments during the 7- to 13-d period (2 to 5%; P < 0.05), regardless of windrowing treatment. With the assistance of continuous ventilation, both litter conditioning and windrowing were able to dry litter effectively. Litter Nutrient Litter ph values of samples at time 0 were close to 7.0, lower than ph values of 8.0 to 9.0 reported in the literature [21, 22]. Litter ph significantly dropped during the windrow period for the windrow treatments (P < 0.05), but not for the control treatment (Table 3). The loss of gaseous ammonia likely contributed to the decrease in ph. No significant difference between

6 630 JAPR: Research Report Table 2. Maximum internal temperatures for control house and 2 windrow houses, and time (h) exceeding temperatures of 40, 50, and 55 C for 5 consecutive trials 1 T max, C Time >40 C, h Time >50 C, h Time >55 C, h Trial Control W_1 W_2 W_1 W_2 W_1 W_2 W_1 W_ N/A Control = nonwindrow house; W_1 = windrow house with low-moisture litter; W_2 = windrow house with high-moisture litter; T max = maximum internal temperature; N/A = not available. time 0 and time 1 occurred for any treatment in regard to total nitrogen concentration, except for a slight increase in the windrow treatment with high moisture (W_2). Windrows resulted in a slight but significant decrease in total carbon (P < 0.05). Surprisingly, some water-soluble nutrients decreased in windrow treatments. This was observed for Ca, K, S, B, Fe, Cu, Al, and Mn. However, Mg and P increased in solubility in windrow treatments (P < 0.05; Table 4). The increase in P solubility is likely due to the mineralization of phytate-p [23, 24]. The control treatment consistently resulted in a significant increase in water-soluble nutrients, suggesting that an appreciable degree of biotic and abiotic activity occurred in the control treatment after flocks were removed. Changes in the total concentrations of nongaseous nutrients are indicators of changes in the mass of the litter material (i.e., oxidation of organic matter to water and carbon dioxide). When organic matter is degraded and the nongaseous nutrients remain, it makes the total concentration of these nutrients increase even though the total mass of the nongaseous nutrients remains unchanged. For the windrow treatments, few significant changes in total nutrient Figure 1. Temperature (T) profiles of windrowed (W_1 and W_2) and nonwindrowed litter (control) and the air temperature inside the house (T_air) and outside (T_out).

7 Liang et al.: BROILER LITTER WINDROWING 631 Table 3. Mean 1 litter moisture content, ph, total nitrogen (TN), and total carbon (TC) content of litter samples collected at the onset (time 0) and end (time 1) of litter management for 5 consecutive trials Moisture, % ph TN, % of DM TC, % of DM Item 2 Time 0 Time 1 SEM Time 0 Time 1 SEM Time 0 Time 1 SEM Time 0 Time 1 SEM Control 21.5 a 15.9 b b 7.15 a b 33.0 a 0.44 W_ a 14.6 b a 6.79 b a 30.7 b 0.23 W_ a 17.3 b a 6.75 b b 3.56 a a 31.5 b 0.29 a,b Different superscripts within a row, within a parameter indicate significant differences (P < 0.05). 1 Data shown are the means of 5 trials and 8 sampling points per trial and time. 2 W_1 = windrow house with low-moisture litter; W_2 = windrow house with high-moisture litter. Table 4. Mean 1 water-soluble elements (mg/kg, dry weight basis) of litter samples collected at the onset (time 0) and end (time 1) of litter management for 5 consecutive trials Na Ca Mg K P Item Time 0 Time 1 SEM Time 0 Time 1 SEM Time 0 Time 1 SEM Time 0 Time 1 SEM Time 0 Time 1 SEM Control 7,475 b 8,357 a 162 1,122 1, b 1,092 a 51 22,307 b 24,117 a 303 1,686 b 2,096 a 105 W_1 2 7,669 a 7,401 b 120 1,243 a 1,126 b ,247 a 21,384 b 189 1,736 b 1,885 a 70 W_2 2 8,114 a 7,817 b 120 1,288 a 1,159 b b 981 a 44 23,820 a 23,117 b 236 1,738 b 2,106 a 87 a,b Different superscripts within a row, within a parameter indicate significant differences (P < 0.05). 1 Data shown are the means of 5 trials and 8 sampling points per trial and time. 2 W_1: windrow house with low moisture litter; W_2: windrow house with high moisture litter.

8 632 JAPR: Research Report Table 5. Mean 1 total phosphorus, calcium, and potassium (dry weight basis) collected at the onset (time 0) and end (time 1) of litter management for 5 consecutive trials and calculated degradation (% deg) of litter samples based on those concentrations P, mg/kg Ca, mg/kg K, mg/kg % deg by K % deg by Ca % deg by P Time 0 Time 1 SEM Time 0 Time 1 SEM Time 0 Time 1 SEM Item 2 Control 15,057 b 17,355 a ,603 b 33,450 a ,623 b 28,348 a W_1 14,603 14, ,260 30, ,971 25, W_2 16,074 b 16,539 a ,483 32, ,436 b 27,319 a a,b Different superscripts within a row, within a parameter indicate significant differences (P < 0.05). 1 Data shown are the means of 5 trials and 8 sampling points per trial and time. 2 W_1 = windrow house with low-moisture litter; W_2 = windrow house with high-moisture litter. concentrations were observed (Table 5). Alternatively, the control treatment often had significantly higher total nutrient concentrations 7 to 10 d after flocks were removed. Among these nutrients, P, Ca, and K are the most reliable for calculating percent degradation due to their high abundance and ease in solubilization during digestion. Based on that, it appears that the control treatment had more degradation than the windrow treatments. Reasons for this are unknown; however, it seems as though the windrow conditions were less conducive to organic matter degradation compared with the control treatment that was not windrowed. Ultimately, no negative effect of windrow treatments on litter quality was noted with regard to agronomic applications. Both the control and windrow treatments resulted in a decrease in litter moisture content, which is likely beneficial to bird health conditions. Microbial Flocks 2 and 5 had d 0 (time 0) and 7 (time 1) litter samples analyzed for Clostridium spp., E. coli, and Staph. aureus populations. The minimum detection limit was 2 log cfu/g. For data comparison, all nondetect values were assigned one-half the detection limit (1 log cfu/g). In flocks 2 and 5, Clostridium and E. coli were detected (Table 6); however, Staph. aureus was undetectable in either flock (data not shown). Clostridium populations were reduced to below the detection limit in treatment groups from d 0 to 7; however, reductions were not significant. Escherichia coli populations were reduced to below the detection limit in both treatment and control groups from d 0 to 7; however, significant reductions were only reported in the higher moisture windrow (W_2) treatment. This may have been due to a higher starting population of E. coli recovered from the higher moisture windrow group. The continuous high temperatures (>55 C) achieved through proper composting will destroy most pathogens and viruses [25 28]. Internal windrow temperatures in all treatment groups were >55 C. The lack of significant differences found in Clostridium and E. coli populations may have been due to a low population level recovered on d 0 and the small sample size. Cumulative mortality rates of first

9 Liang et al.: BROILER LITTER WINDROWING 633 Table 6. Average log cfu/gram 1 of Clostridium spp. and Escherichia coli of surface and internal litter samples in flocks 2 and 5 Clostridium E. coli Item 2 d 0 d 7 SEM d 0 d 7 SEM Control surface Trial Trial W_1 surface Trial Trial W_2 surface Trial Trial a 1.0 b 0.25 W_1 internal Trial Trial W_2 internal Trial Trial a,b Different superscripts within a row, within a parameter indicate significant differences (P < 0.05). 1 Average of 3 composite litter samples. 2 W_1 = windrow house with low-moisture litter; W_2 = windrow house with high-moisture litter. 7-d after chick placement were not significantly different, ranging from 0.4 to 2.4%. Foot Scores All scores were relatively low for all flocks and houses (Table 7). Flock 4 had no differences in foot scores, whereas flock 5 in the control house had a significantly higher foot score than W_1 house. Flock 6 had no significant difference in foot scores for the 2 treatments. When all flocks were combined, a significant difference (P < 0.05) was observed, with the windrowed house having a lower (or better) foot score. Whereas many factors contribute to foot pad dermatitis, the primary factor appears to be litter moisture content [29]. Windrow process completely shifts litter and redistributes moisture away from water lines. Although litter moisture levels of control and windrow houses in the present study were not statistically different, it is speculated that areas under water lines could be drier in windrow houses than those of control houses for the first few days of brooding. The inconsistency of the results indicates other contributing factors existed. Litter Production Litter depths in the windrowed house increased from 7.3 cm at the end of the first flock to 13.8 cm at the end of the fifth flock (Figure 2). Litter bulk density averaged 531 kg/m 3. This was lower than the density of 600 to 705 kg/m 3 reported previously [30], which could be affected by difference of bedding materials (100% rice hulls in earlier study), ventilation, and drinker management. As a result of density and depth measurement in the current study, total litter mass calculated was 114 t at the end Table 7. Average foot scores from chickens of 3 flocks raised on windrowing or nonwindrowing litter Treatment Flock 4 Flock 5 Flock 6 All flocks combined Nonwindrow a a Windrow b b SEM P-value a,b Different superscripts within a column indicate significant differences (P < 0.05).

10 634 JAPR: Research Report therefore less accumulation of litter mass at the end of flock 5. Ammonia Concentration after Windrowing Figure 2. Density and depth of accumulated broiler litter from 5 consecutive flocks in a commercial broiler house and corresponding quantity of litter. of a 5-flock grow-out, compared to 134 t at the end of a 6-flock grow-out [31]. The 3-mo resting period from early December 2011 to February 2012 could have resulted in extended mass loss, Windrows were spread out on d 7 in May 2011 (trial 1). Houses were ventilated for 3 d at ambient temperatures before being preheated with minimum ventilation (120 s on s off with three 0.9-m diameter fans) starting d 10. Preheat intentionally started early for this flock to test the ammonia concentrations as a result of windrowing. Ammonia levels rose from <10 ppm under ambient condition to >30 ppm at house temperature of around 30 C. Ammonia levels persisted at 30 ppm for 3 d under the minimum ventilation rates (Figure 3). Ammonia concentration level dropped to around 15 ppm on d 15 (from onset of windrow) before bird placement. At least 4 d were necessary to purge ammonia with proper ventilation before the ammonia level was suitable for chick placement. Trial 3 windrows were spread out on d 13 (Sep. 27, 2011). The W_1 house was ventilated by two 1.2-m diameter fans for more than 24 h before programmed into minimum ventilation (three 0.9-m diameter exhaust fans on timer of 40 s on s off). Ammonia concentrations Figure 3. Hourly ammonia concentrations in brood section and corresponding ventilation rates before chick placement (trial 1). bd = bird.

11 Liang et al.: BROILER LITTER WINDROWING 635 Figure 4. Hourly ammonia concentrations in brood section and corresponding ventilation rates before and after litter amendment was applied to brood section, a day earlier than chick placement (trial 3). were >40 ppm in the initial minimum ventilation stage (Oct. 5, 2011; Figure 4). Litter amendment was applied to the brood section 24 h before chick placement, based on integrator recommendation (0.49 kg/m 2 ). Ammonia concentrations dropped below 10 ppm 12 h after amendment application and stabilized around 10 ppm at time of chick placement. Litter amendment was effective in reducing ammonia volatilization from windrowed litters, especially if time is short before chick placement. Assuming litter amendment costs $0.66 per kg, the expense of a low-dose application in a half-house brood section is about $240. This cost was lower than the scenario of higher fan run time during cold weather with no addition of a litter amendment, which could easily exceed propane usage of 400 L per day ($190 fuel per day assuming $0.47/L of propane). Ammonia Emissions High transient ammonia emissions occurred during windrow construction, turning, and spreading (Figure 5). Average ammonia emission rate during the 5 windrow periods was 6.52 ± 1.74 kg/d per house. Researchers [32] previously reported an average ammonia emission of 8.77 ± 8.27 kg/d per house with no birds in a broiler house (dimensions of m). The ammonia emissions from the current study were slightly lower than previous studies, likely due to lower litter moisture, less litter mass, or smaller floor area (therefore lower emitting surface). In our study, hourly NH 3 emissions up to 3,800 g/h per house were recorded using litter windrowing, compared with between 212 to 1,107 g/h per house from a typical litter management of blading, disking, and harrowing reported elsewhere [33]. The average ammonia emission rate during grow-out periods from 4 flocks of complete data was 8.65 ± 1.60 kg/d per house (excluding 2 incomplete data collected during flocks 2 and 3). Cumulative ammonia emission during a flock increased from flock 1 raised on new beddings to flock 6 raised on built-up litter (Figure 6). Higher average emission rates (14.55 ± 8.99 kg/d per house) were found for flocks reared to 52 d of market age [31]. The reason for lower ammonia emission rates from our study could be due to the smaller house size, younger market age (48 d), and the lower ph values of the litter (Table 3). Ammonia emitted from windrowing

12 636 JAPR: Research Report Figure 5. Hourly ammonia emission rates (ER) during 5 windrow trials from 2 windrow houses (W_1 and W_2). periods was about 13% of that emitted during grow-out cycles on an annual basis. CONCLUSIONS AND APPLICATIONS 1. Higher litter moisture content resulted in higher windrow temperature. 2. Litter moisture content decreased from both windrow and nonwindrow treatments. 3. Clostridium spp. populations were reduced to below the detection limit in treatment groups after 7 d of windrowing; however, significant reductions Figure 6. Cumulative ammonia emission rates (ER) during windrowing and grow out cycles from windrow 1.

13 Liang et al.: BROILER LITTER WINDROWING 637 were not observed. Escherichia coli populations were reduced to below the detection limit after 7 d of windrowing, but treatment effects were not observed. The lack of significant differences in Clostridium and E. coli populations may have been due to a low population level recovered on d 0 and the small sample size. 4. Foot scores were similar in the windrow and control houses in 2 of the 3 flocks evaluated, but were better in the windrow than control house in 1 of 3 flocks evaluated. 5. Without litter amendment, at least 4 d with proper ventilation were necessary to purge ammonia during preheating before chick placement. Alternatively, litter amendment at low dose was effective in reducing ammonia volatilization after windrowing and was more economical than operating fans in winter condition. 6. Ammonia emissions were high during windrowing activities and immediately following windrow spreading. Litter windrowing contributed about 13% of the estimated annual ammonia emissions. REFERENCES AND NOTES 1. Haug, R. T The Practical Handbook of Compost Engineering. CRC Press Inc., Boca Raton, FL. 2. Macklin, K. S., J. B. Hess, and S. F. Bilgili In-house windrow composting and its effects on food borne pathogens. J. Appl. Poult. Res. 17: Macklin, K. S., J. B. Hess, S. F. Bilgili, and R. A. Norton Effects of in-house composting of litter on bacterial levels. J. Appl. Poult. Res. 15: Barker, K. J., C. D. Coufal, J. L. Purswell, J. D. Davis, H. M. Parker, M. T. Kidd, C. D. McDaniel, and A. S. Kiess In-house windrowing of a commercial broiler farm during the summer months and its effect on litter composition. J. Appl. Poult. Res. 20: Priefert Litter Back Blade, Priefert Manufacturing Co. Inc., Mt. Pleasant, TX. 6. Priefert 7 Litter Saver, Model 90, Priefert Manufacturing Co. Inc., Mt. Pleasant, TX. 7. Lewis Brothers Manufacturing Inc., Baxley, GA. 8. TMC50-HD, Onset Computer Corp., Bourne, MA. 9. HOBO U12 4-channel, Onset Computer Corp., Bourne, MA. 10. HOBO U Pro v2, Onset Computer Corp., Bourne, MA. 11. EPA 3050 acid digestion method followed by inductively couple argon plasma-atomic emission spectroscopy solution analysis. Environmental Protection Agency Acid digestion of sediments, sludges, and soils. Method In SW-846. Test Methods for Evaluating Solid Waste. Vol. 1. Environmental Protection Agency, Washington, DC. 12. Nelson, D. W., and L. E. Sommers Total carbon, organic carbon, and organic matter. Pages in Methods of Soil Analysis. Part 3: Chemical Methods. D. L. Sparks, A. L. Page, P. A. Helmke, R. H. Loeppert, P. N. Soltanpour, M. A. Tabatabai, C. T. Johnston, M. E. Sumner, ed. Soil Science Society of America Inc., American Society of Agronomy, Inc., Madison, WI. 13. Remel, Lenexa, KS. 14. Nagaraj, M., C. A. P. Wilson, J. B. Hess, and S. F. Bigili Effect of high-protein and all-vegetable diets on the incidence and severity of pododermatitis in broiler chickens. J. Appl. Poult. Res. 16: Innova 1412, Innova AirTech Instruments A/S, Ballerup, Denmark. 16. CR1000, Campbell Scientific Inc. Logan, UT. 17. Model 264, Setra, Boxborough, MA. 18. HMT100, Vaisala, Finland. 19. Ammonia emission rate calculation: 3 e ER = Q ρ NH NH e e i e i = 1 ρ w T P m std a, V T P m a std where ER = ammonia emission rate for the house (g/hr per house); Q e = ventilation rate of the portion of the house at location e (sidewall or tunnel end) at field temperature and barometric pressure (m 3 /hr per house); [NH 3 ] i, [NH 3 ] e = NH 3 concentration of incoming or exhaust house ventilation air in ppm; w m = molecular weight of ammonia, g/ mol; V m = molar volume of NH 3 gas at standard temperature (0 C) and pressure (1 atm), m 3 /mol; T std = standard temperature, K; T a = absolute house temperature, ( C ) K; P std = standard barometric pressure, kpa; P a = atmospheric barometric pressure for the site elevation, kpa; ρ e or ρ i = air density at outside or incoming location, kg da m 3 moist air. 20. SAS Institute Statistical Analysis Software. Version 9.3. SAS Inst., Cary, NC. 21. Singh, A., J. R. Bicudo, A. L. Tinoco, I. F. Tinoco, R. S. Gates, K. D. Casey, and A. J. Pescatore Characterization of nutrients in built-up broiler litter using trench and random walk sampling methods. J. Appl. Poult. Res. 13: Coufal, C. D., C. Chavez, P. R. Niemeyer, and J. B. Carey Effects of top-dressing recycled broiler litter on litter production, litter characteristics, and nitrogen mass balance. Poult. Sci. 85: Warren, J. G., C. J. Penn, J. M. McGrath, and K. Sistani The impact of alum additions on organic P transformations in poultry litter and soils receiving alum-treated poultry litter. J. Environ. Qual. 37: Penn, C. J., J. Vitale, S. Fine, J. Payne, J. G. Warren, H. Zhang, M. Eastman, and S. L. Herron Alternative poultry litter storage for improved transportation and use as a soil amendment. J. Environ. Qual. 40: Glanville, T. D., T. L. Richard, J. D. Harmon, D. L. Reynolds, and S. S. Sadaka Environmental impact

14 638 JAPR: Research Report and biosecurity of composting for emergency disposal of livestock mortalities. Proc. Am. Soc. Ag. Eng. Annu. Int. Meet. Las Vegas, NV. American Society of Agricultural & Biological Engineers, St. Joseph, MO. 26. Kalbasi, A., S. Mukhtar, S. E. Hawkins, and B. W. Auvermann Carcass composting for management of farm mortalities: A review. Compost Sci. Util. 13: Kalbasi, A., S. Mukhtar, S. E. Hawkins, and B. W. Auvermann Design, utilization, biosecurity, environmental and economic considerations of carcass composting. Compost Sci. Util. 14: Wilkinson, K. G The biosecurity of on-farm mortality composting. J. Appl. Microbiol. 102: Tabler, T., J. Wells, H. M. Yakout, and Y. Liang What Causes Footpad Dermatitis in Poultry? Publication Mississippi State University Extension Service. 30. Brewer, S. K., T. A. Costello, and I. L. Berry Mass, bulk and nutrient accumulation in re-used broiler litter. Paper No ASAE Annual Meeting, ASABE, St. Joseph. MO. 31. Liang, Y., G. T. Tabler, and K. W. VanDevender Ammonia emissions from downtime litter management in broiler housing. Proc. Int. Sym. Air Qual. Manure Manag. Ag., Dallas, TX. American Society of Agricultural & Biological Engineers, St. Joseph, MO. 32. Burns, R. T., H. Xin, R. S. Gates, H. Li, D. G. Overhults, L. Moody, and J. Earnest Ammonia emissions from broiler houses in the southeastern United States. Proc. Int. Sym. Air Qual. Waste Manag. Ag. Sept. 2007, American Society of Agricultural & Biological Engineers, St. Joseph, MO. 33. Topper, P. A., E. F. Wheeler, J. S. Zajaczkowski, R. S. Gates, H. Xin, Y. Liang, and K. D. Casey Ammonia emission from two empty broiler houses with built-up litter. Trans. ASAE 51: Acknowledgments Funding for this project was provided by the United States Poultry and Egg Association (Tucker, GA) and the University of Arkansas Division of Agriculture (Little Rock). The authors thank Chance Williams and David Mc- Creery (University of Arkansas, Fayetteville) for their assistance with the experiments.