J. Appl. Poult. Res.
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J APPL POULT RES 2008. 17:348-353. doi:10.3382/japr.2007-00113
© 2008 Poultry Science Association
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Research Reports

Vertical Stratification of Ammonia in a Broiler House1

D. M. Miles2

USDA-ARS, Genetics and Precision Agriculture Research Unit, 810 Hwy 12 East, MS State, MS 39762

2 Corresponding author: dana.miles{at}ars.usda.gov


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
The broiler industry is not immune to the problematic nature of NH3 production in animal rearing facilities. Though the headlines of today focus on environmental impact considerations, the detrimental effects of the house air quality on farmers and birds remain considerable for industry viability. This research investigated the vertical stratification of in-house NH3 combined with sampling position down the center of the house and with different NH3 analysis technologies. The results indicated that reuse of litter and house ventilation correlate to trends in NH3 concentration at particular measurement heights. When tunnel ventilation was primary, NH3 concentrations decreased vertically with increasing distance from the litter surface. However, with lower outside temperatures, little ventilation, and a stagnant house atmosphere, no concentration gradient was evident. The work also demonstrated significant variability among professionally calibrated instruments and traditionally used pull tubes. Characterization of interior air quality of broiler houses should consider sampling height to effectively address bird exposure.

Key Words: ammonia • broiler • litter • house management


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Gaseous NH3 is produced from the microbial breakdown of nitrogenous compounds, including uric acid, in poultry feces. Ventilation rate, litter temperature, pH, and moisture influence its volatilization from broiler litter [1, 2]. Delayed clean-out and practices designed to conserve energy (e.g., low ventilation rate, limited area brooding) intensify the pollutant gas concentration within houses [3, 4]. Ocular and respiratory disorders [1, 2, 5, 6] as well as diminished performance (at 50 ppm [7] and at 25 ppm [8]) in broilers have been reported in conjunction with NH3 exposure.

The principal focus regarding NH3 today is the quantity exiting animal facilities. A nationwide, 2-yr monitoring study (2006 to 2008), the US EPA Air Quality Consent Agreement, is underway to develop baseline emission factors for animal facilities. For broilers, the NH3 concentration measured near exhaust fans is coupled with building ventilation rates to develop emission factors [9]. The samples measured near the exhaust may not be relevant to the concentration experienced by the birds. Though many nterrelated parameters affect emission factors, increased bird and litter age have been linked to increased emission factors [9, 10]

Accurately measuring NH3 in broiler rearing facilities is not trivial. Ammonia molecules are highly water soluble; their polarity and geometry increase the tendency to adsorb onto surfaces, causing potentially erroneous readings when samples are transported through tubing [11], even to a highly accurate (and high-cost) instrument (e.g., chemiluminescent or photoacoustic, >$25,000). Lower-cost alternatives, such as electrochemical types ($500 to $2,000), have been designed for NH3 leak detection in other industries but cannot withstand the constancy of NH3 concentration in broiler houses without rejuvenation and periodic calibration [12]. Affordable NH3 detection equipment is sorely needed for on-farm interior air quality assessment and control, because farmers and service personnel may become desensitized (unable to detect even high concentrations) with continued exposure to NH3 [13].

Ammonia is lighter than air and, thus, may initially be thought to have greater concentrations with increasing height from the floor. However, the broiler house floor-litter provides the source of NH3, and the birds may effectively insulate air flow (and arrest dilution) near the floor. Beyond these gross physical factors, dynamic relationships exist for NH3 release from the litter pore space to the house air. The hypothesis of this research is that a vertical stratification of NH3 exists in broiler houses where the concentration is greater near the floor. Knowledge of concentration at bird height is lacking. The objectives of this work were (1) to determine the vertical characteristics of NH3 concentration inside a broiler house under commercial management and (2) to compare instruments for single point measurements of NH3 concentration.


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
The research described here occurred during the first 2 broiler growouts after total cleanout and replacing the house bedding with clean wood shavings. Pine shavings (200 yd3 of green shavings) were placed on the house soil pad at an approximate depth of 4 in. House maintenance between flocks included removing approximately 6.5 loads (175 ft3/load) of cake, with moisture ranging from 24 to 44%, using a Lewis Brothers No. 4 Housekeeper [14]. The commercial, curtain-sided house measured 43 x 400 ft and is located in Mississippi. Bird and house management were prescribed by the integrator, which determined the environmental conditions under which the research was conducted. Gas and litter sample characteristics are reported for d 40 of flock 1, which was in the middle of September (fall), and on d 42 of flock 2, early in December (winter). Both flocks had a nominal chick placement of 21,000, and NH3 samplings were carried out with the curtains completely closed.

Measurements were performed at 3 positions down the center of the broiler house. The middle position was the lengthwise midpoint of the house; a second position was 100 ft toward the cooling pad end of the house relative to the middle; and the final position was located 100 ft away from the middle toward the exhaust fans at the end of the house. Near the end of each flock, litter samples (approximately 0.75 gal) were collected from the upper 1 in. of the litter surface at each position. Samples were analyzed for moisture, pH, and nutrient content. Clean shaving samples collected before the first flock were subjected to the same analyses. Moisture was determined by loss in weight after drying bedding samples for 48 h at 65°C, and pH was measured using a litter:deionized water ratio of 1:5. Nutrients were determined via combustion analysis (% N) [15] and inductively coupled plasma (% P, % K) [16]

Other parameters determined at each site included litter and air temperature, relative humidity, and air speed. Litter surface temperature was measured at each position using an infrared thermometer [17]. A pocket weather meter [18] was used to measure ambient house temperature (°F), relative humidity (%), and air speed (mph) at each position down the house as well as at each vertical sampling location, described below.

NH3 Measurements
Ammonia concentration during the 2 flocks was measured at each position and included the addition of measurements at vertical sampling heights. The vertical sampling locations were as follows: (1) the litter surface, (2) 1 ft above the litter surface (approximately bird beak height), and (3) at 3.3 ft from the litter surface (a comfortable position for the person performing the measurement, such as the grower or service person might measure).

Three different measurement technologies were used to measure the aerial NH3 concentration. These included a photoacoustic multigas analyzer [19], 2 (same model and calibration history) portable electrochemical gas leak detectors [20], and traditional pull tubes [21]. All sampling was performed in triplicate in succession. The experimental design was a completely randomized design with a factorial treatment structure of 3 vertical sampling heights and 4 instrument types. House position, relative to the center of the house, was also included in the model. Sampling heights and house positions were measured randomly for each flock. The pump cycle for the photoacoustic analyzer (approximately 70 s) determined the interval for simultaneously recording the measurement value from each of the 4 instruments. Because of the range among the data, log transformation was utilized with the MIXED procedure of SAS [22]. Log means transformed back to the original scale are defined as geometric means, which provide a better measure of centrality for the data than arithmetic means. Geometric means with the probability of observing significant differences among the treatments, based on {alpha} = 0.05, are reported in Figures 1Go, 2Go, and 3Go.


Figure 1
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  		Figure 1. Geometric means for NH3 concentration at the vertical measurement locations: the litter surface, 1 ft above the surface, and 3.3 ft above the litter surface for d 40 of flock 1 (mid-September on fresh litter) and d 42 of flock 2 (early December on reused litter). For each flock, differing letter designations indicate significant differences in measurement height for NH3 concentration (P ≤ 0.05; flock 1 LSD = 1.07 ppm; flock 2 Lsd = 1.04).

 

Figure 2
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  		Figure 2. Geometric means for NH3 concentration measured down the center of the house at positions: 100 ft toward cooling pads, middle, and 100 ft toward exhaust fans, on d 40 of flock 1 (mid-September on fresh litter) and d 42 of flock 2 (early December on reused litter). For each flock, differing letters indicate significant differences down the center of the house for NH3 concentration (P ≤ 0.05; flock 1 LSD = 1.07 ppm; flock 2 LSD = 1.04).

 

Figure 3
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  		Figure 3. Geometric means for NH3 concentration measured by various instruments: the Innova photoacoustic multigas analyzer, 2 electrochemical gas leak detectors (Manning 1 and 2), and pull tubes for d 40 of flock 1 (mid-September on fresh litter) and d 42 of flock 2 (early December on reused litter). For each flock, differing letters indicate significant differences among instruments for NH3 concentration (P ≤ 0.05; flock 1 LSD = 1.08 ppm; flock 2 LSD = 1.05)

 

   RESULTS AND DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Flocks 1 and 2 demonstrate dissimilar trends in the vertical distribution of NH3 (Figure 1Go). As measurement height increases in flock 1, the mean concentration of NH3 decreases from 11.2 to 4.4 ppm, supporting the hypothesis that the birds can be subjected to greater concentrations that may not be reflected in measurements made above them. However, in flock 2, the litter surface and 3.3-ft height concentrations appear similar (23.5 and 23.0 ppm), whereas the 1-ft height exhibits lower NH3 (20.6 ppm). These differing trends are likely attributed to the differences in ventilation between the fall and winter seasons, as evidenced by the measured air speed, relative humidity, and air and litter temperatures on the sampling days of each flock. Relative humidity was noticeably greater in flock 1 vs. flock 2 (84.8 ± 1.0 vs. 51.7 ± 2.1%), whereas air temperatures were more analogous between the flocks, 74.9 ± 0.9°F in the first flock and 72.0 ± 1.4°F in the second. Also, litter temperatures were comparable, 77.2 ± 0.3°F in flock 1 and 73.8 ± 1.9°F in flock 2. Air speeds averaged 4.8 ± 0.9 mph in flock 1 and 0.6 ± 0.6 mph in flock 2. Ventilation rates (air speed) through the house are greater during warmer days to cool the broilers late in the growout and are lower during cooler days. Exterior house temperature for d 40, flock 1 during the 10:00 a.m. measurement was 80.2°F, whereas d 42 of flock 2, the outside temperature at this same time of day was 59.5°F

In a similar fashion, flock 1 and flock 2 differ with respect to house sampling position measurements (Figure 2Go). In flock 1, moving from near the cooling pads toward the exhaust fans, the NH3 levels increase significantly for each 100-ft position change (4.6, 7.0, and 9.4 ppm). However, for flock 2, the winter flock with decreased ventilation, the measured NH3 concentrations do not differ significantly (21.9, 22.4, and 22.7 ppm). Inference provides that these results are again attributed to the differing ventilation for each season. The movement of air on d 40 in flock 1 may be characterized as tunnel mode, generating air speeds from 3 to 5.8 mph, whereas the low rates (up to only 1.2 mph) or lack of any measured air flow in flock 2 typify a stagnant atmosphere.

Figure 3Go presents the comparison of state-of-the-art technology (photoacoustic), which is the only instrument evaluated that accounts for moisture in the sample, to more common methods (electrochemical and colorimetric) used in NH3 broiler research. The variability among the methods is present in both flocks and is not consistent between the flocks. Although the electrochemical gas leak detectors (Manning 1 and 2) had been calibrated by the manufacturer before the experiment, they differed from one another during the sampling of both flocks. Assuming the most accurate measurement was performed by the photoacoustic instrument (Innova) [23], Manning 1 exceeded the actual aerial NH3 concentration in flock 1 but was similar to the Innova in flock 2. Relatively, Manning 2 and the pull tubes underestimated the aerial concentration in both flocks. In flock 1, the two exhibited similar readings, but the pull tubes were substantially less than all other instruments in flock 2.

Debatable operation of pull tubes has been previously shown. Wheeler et al. [13] reported the pull tube uncertainty within approximately 25% of the actual concentration (±12.5 ppm if the actual is 50 ppm), having evaluated the tubes and an electrochemical sensor [24] in commercial layer houses. Though the instruments operated satisfactorily when subjected to 50 ppm calibration gas, tube accuracy was questionable in the low level environment of the houses. The study also found that the electrochemical sensor required frequent calibration and was prone to drift [13].

The greater magnitude of NH3 in the house in flock 2, the winter growout on reused litter, can be seen in Figures 1Go, 2Go, and 3Go. It was expected that the second flock on the reused pine shavings would yield greater NH3 in the house atmosphere. For broilers grown on reused litter (4 to 5 flocks), a recent study reported that NH3 could not be maintained below 25 ppm during minimum ventilation [25]. In flock 1, mean NH3 concentration ranged from 4.3 to 12.1 ppm, but in flock 2, the range was 14.7 to 27 ppm NH3.


   CONCLUSIONS AND APPLICATIONS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
REFERENCES AND NOTES
 

  1. Trends in vertical stratification of NH3 concentration in a broiler house correlate to ventilation rate. During tunnel ventilation at the end of flock 1 (on new litter), NH3 concentration decreased vertically with increasing distance from the litter surface. However, in the lower ventilation regime of flock 2 (on reused litter), the litter surface and 3.3-ft measurements were similar.
  2. If the objective for NH3 quantification is to assess bird exposure, the height of the measurement should be placed at bird height and the performance (e.g., relative accuracy) of the type of measuring device should be considered by the integrator, grower, or researcher.
  3. Proper and up-to-date instrument calibration is essential to the accuracy of determining aerial NH3 concentrations.


   FOOTNOTES
 
1 Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA. Back


   REFERENCES AND NOTES
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 

  1. Al Homidan, A., J. F. Robertson, and A. M. Petchey. 2003. Review of the effect of ammonia and dust concentrations on broiler performance. Worlds Poult. Sci. J. 59:340–349.[CrossRef][Web of Science]
  2. Anderson, D. P., C. W. Beard, and R. P. Hanson. 1964. The adverse effects of ammonia on chickens including resistance to infection with Newcastle disease virus. Avian Dis. 8:369–379.[CrossRef][Web of Science]
  3. Carr, L. E., F. W. Wheaton, and L. W. Douglass. 1990. Empirical models to determine ammonia concentrations from broiler chicken litter. Trans. ASAE 33:1337–1342.[Web of Science]
  4. Reece, F. N., B. J. Bates, and B. D. Lott. 1979. Ammonia control in broiler houses. Poult. Sci. 58:754–755.[Web of Science]
  5. Charles, D. R., and C. G. Payne. 1966. The influence of graded levels of atmospheric ammonia on chickens. I. Effects on respiration and on the performance of broilers and replacement growing stock. Br. Poult. Sci. 7:177–187.[Medline]
  6. Valentine, H. 1964. A study of the effect of different ventilation rates on the ammonia concentrations in the atmosphere of broiler houses. Br. Poult. Sci. 5:149–159.[CrossRef]
  7. Miles, D. M., S. L. Branton, and B. D. Lott. 2004. Atmospheric ammonia is detrimental to the performance of modern commercial broilers. Poult. Sci. 83:1650–1654.[Abstract/Free Full Text]
  8. Reece, F. N., B. D. Lott, and J. W. Deaton. 1981. Low concentrations of ammonia during brooding decrease broiler weight. Poult. Sci. 60:937–940.[Web of Science]
  9. Casey, K. D., R. S. Gates, E. F. Wheeler, H. Xin, J. L. Zajaczkowski, P. A. Topper, and Y. Liang. 2004. Ammonia emissions from Kentucky broiler houses during winter, spring, and summer. Paper No. 29 in Proc. A&WMA’s 97th Annu. Conf. and Exhib.: Sustainable Development: Gearing Up for the Challenge, Indianapolis, IN. Air and Waste Manage. Assoc., Pittsburgh, PA.
  10. Redwine, J. S., R. E. Lacey, S. Mukhtar, and J. B. Carey. 2002. Concentration and emissions of ammonia and particulate matter in tunnel-ventilated broiler houses under summer conditions in Texas. Trans. ASAE 45:1101–1109.[Web of Science]
  11. Mukhtar, S., A. J. Rose, S. C. Capareda, C. N. Boriack, R. E. Lacey, B. W. Shaw, and C. B. Parnell Jr. 2003. Assessment of ammonia adsorption onto Teflon and LDPE tubing used in pollutant stream conveyance. Agric. Eng. Int., CIGR J. Sci. Res. Dev. 5:1–13.
  12. Xin, H., T. Wang, R. S. Gates, E. F. Wheeler, K. D. Casey, and A. J. Heber. 2002. A portable system for continuous ammonia measurement in the field. Paper 024168 in Proc. ASAE Annu. Int. Mtg./CIGR XVth World Congress, Chicago, IL. Am. Soc. Agric. Eng., St. Joseph, MI.
  13. Wheeler, E. F., R. W. J. Weiss, and E. Weidenboerner. 2000. Evaluation of instrumentation for measuring aerial ammonia in poultry houses. J. Appl. Poult. Res. 9:443–452.[Abstract/Free Full Text]
  14. Lewis Bros., Baxley, GA.
  15. Thermo Finnigan model Flash EA1112 Series, Elan-tech Inc., Lakewood, NJ.
  16. Model 1000, Thermo Jarrell-Ash, Franklin, MA.
  17. Raynger ST, Raytek Corporation, Santa Cruz, CA.
  18. Kestril 3000, Nielsen Kellerman, Chester, PA.
  19. Innova 1312, California Analytical, Orange, CA.
  20. EC-P1, Honeywell Analytics, Lincolnshire, IL.
  21. Gastec detector tubes, no. 3L (0.5 to 78 ppm, using 1 pump for the optimal range of 0 to 30 ppm), in conjunction with a Sensidyne/Gastec pump (kit 800), Nexteq, Tampa, FL.
  22. SAS Institute, Inc. 2000. SAS System for Microsoft Windows. Version 8 (TS M1). SAS Institute Inc., Cary, NC.
  23. Gates, R. S., J. L. Taraba, N. S. Ferguson, and L. W. Turner. 1997. A technique for determining ammonia equilibrium and volatilization from broiler litter. Paper no. 974074 in the Proceedings for the ASAE Annual International Meeting, Minneapolis, MN. Am. Soc. Agric. Eng., St. Joseph, MI.
  24. Drager PolytronII, Draeger Safety Inc., Pittsburgh, PA.
  25. Wheeler, E. F., K. D. Casey, J. S. Zajaczkowski, P. A. Topper, R. S. Gates, H. Xin, Y. Liang, and A. Tanaka. 2003. Ammonia emissions from U.S. poultry houses: Part III–Broiler houses. Pages 159–166 in Proc. 3rd Int. Conf.: Air Pollution from Agricultural Operations III, Research Triangle Park, NC. ASAE Publ. No. 701P1403. Am. Soc. Agric. Eng., St. Joseph, MI.




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