- Email: [email protected]
Spatial Distribution of Death Losses in Broiler Flocks
2002 Poultry Science Association, Inc.
Spatial Distribution of Death Losses in Broiler Flocks G. T. Tabler,*,1 I. L. Berry,† H. Xin,† and T. L. Barton§
Primary Audience: Flock Supervisors, Growers, Integrators SUMMARY Mortality in poultry flocks continues to be a major economic loss to broiler growers and integrators. Also, disposal of dead chickens in an environmentally safe manner is becoming increasingly demanding. Accurate descriptions of mortality patterns within broiler houses may prove beneficial with respect to an overall management strategy to minimize death losses during flock growouts. To characterize mortality patterns, locations of dead chickens in four productionscale broiler houses with an east-west orientation were monitored during a 6-mo period in 1992 covering three consecutive flocks in northwest Arkansas. Overall mortality was not affected by the two different ventilation systems used (i.e., conventional cross ventilation with mist cooling in summer vs. tunnel ventilation with pad cooling in summer). Higher mortalities were observed along the north and south sidewalls and centerlines of the houses (e.g., under measurement instruments) and in areas where natural lighting was obstructed (e.g., behind ventilation fans and cooling pads). Key words: broiler, broiler house, conventional ventilation, death location, mortality, tunnel ventilation 2002 J. Appl. Poult. Res. 11:388–396
DESCRIPTION OF PROBLEM Mortality of birds in poultry production facilities represents a major economic loss for poultry producers and the integrators who usually own the birds. Not only do these dead birds represent lost income, they also represent a disposal problem that must be addressed in an environmentally friendly way. Disposal of dead birds becomes an even larger issue for producers each year as more attention is focused on the environment. Further, poultry production continues to increase in areas already 1
crowded with production facilities, and in many instances people are moving into the same areas and suddenly find themselves neighbors with existing production facilities. Mortality at broiler operations can result from a variety of causes. The most predominant causes during the 1992 research period were ascites, sudden death syndrome (SDS), leg problems, and heat prostration. Today, with improved genetics that have somewhat alleviated ascites, leg problems are perhaps a greater area of concern with broilers being held for
To whom correspondence should be addressed: [email protected].
Downloaded from http://japr.oxfordjournals.org/ at East Tennessee State University on June 26, 2015
*Department of Poultry Science, University of Arkansas, Fayetteville, Arkansas 72701; †Department of Biological and Agricultural Engineering, University of Arkansas, Fayetteville, Arkansas 72701; ‡Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, Iowa 50011; and §Department of Poultry Science, Cooperative Extension Service, University of Arkansas, Fayetteville, Arkansas 72701
TABLER ET AL: DEATH LOSS IN BROILER FLOCKS
in younger birds. This leads to the consideration of mortality patterns as a possible means of evaluating localized environments within broiler houses. Most growers and flock supervisors are aware that many dead chickens will be concentrated in certain locations, such as along sidewalls and perhaps near the ends of houses. However, the exact causes of these patterns remains somewhat of a mystery. Do the concentrations result from increased numbers of deaths due to poorer environments in those same areas? Do the concentrations simply result from greater numbers of birds that inhabit a certain area or a greater proportion of time spent in some areas vs. others? Do ailing birds prefer different areas than healthy birds? In response to the questions above, the objectives of this research were to 1) determine and describe spatial distribution of mortality that occurred in typical 1992 broiler growing environments and 2) determine if mortality distribution patterns were associated with environmental variations.
MATERIALS AND METHODS To accurately assess mortality distribution patterns, the location of each dead chicken was recorded daily for three consecutive flocks of 75,200 birds each, from June to December 1992. The birds were the ninth, tenth, and eleventh flocks grown in four commercial-scale broiler houses constructed in 1990, operated by the University of Arkansas and located 12 miles west of Fayetteville, Arkansas, for the purpose of studying energy-efficiency-related to broiler production. Broilers were grown under a standard 1992 industry production contract with a local integrator, who recommended broiler management practices for the flocks. Broiler Houses The four broiler houses were each 40 ft (12.2 m) wide by 400 ft (122 m) long and were equipped with temporary partitions at the lengthwise center for half-house brooding of young chicks. Two houses were constructed with cross-ventilation cooling fans located diagonally along the south wall and low-pressure (120 psi) foggers. The other two houses had
Downloaded from http://japr.oxfordjournals.org/ at East Tennessee State University on June 26, 2015
longer growout periods to reach heavier weights. Heat prostration and SDS continue to be major issues facing the industry. Ascites refers to the accumulation of edematous fluid within the body cavity. Several situations influence its occurrence in broilers: 1) atmospheric hypoxia, 2) housing environment, 3) respiratory diseases, 4) rapid growth rates, 5) high energy diets, 6) toxins, 7) pellets vs. mash, 8) ad libitum vs. restricted feeding, and 9) feed additives such as NaCl [1, 2, 3, 4, 5]. Sudden death syndrome (SDS) is reported as a major cause of death in broiler flocks in many countries around the world [6, 7, 8, 9]. Attempts to cure the disease have, largely, proved unsuccessful. Mortality resulting from heat stress continues to be a problem during hot weather. Increased stocking density and genetic emphasis on faster growth rates along with increased breast meat yield and heavier harvest weights further exacerbate heat-related problems. Reduced feed intake, depressed rates of gain, and increased mortality rates often result when broilers are subjected to high summer temperatures, particularly near the end of the growout cycle. Heat-related mortality has decreased somewhat because of increased insulation and advanced cooling systems (e.g., foggers, misters, evaporative cooling pads) in contemporary production facilities. In addition to the above-mentioned causes of broiler mortality, several other factors may also influence mortality rates. Genetics, sex of bird, health and immune status of breeder flock and hatchery sanitation, longer growout periods, and degree of on-farm culling may all affect mortality within a normal range when acute mortality does not result from temperature stress or disease. Average mortality of male broilers in four production-scale houses over 10 8-wk growth periods was 6.8% [10]. With 6-wk growing periods, mortality can be 4% or less. The increasing production of heavy broilers (8-wk or longer growout periods) for deboning and further processing markets has increased the need for more sophisticated environmental systems in broiler housing. Part of this need results from increased mortality occurring after 6 wk, which represents a much greater financial loss to growers and integrators than mortality
389
390 tunnel ventilation with static pressure-controlled air inlets and evaporative cooling pads. A detailed description of the houses and the environmental control systems was given by Berry et al. [11] and Xin et al. [12]. Flock Management
Data Collection and Analyses The location of each dead chicken in each of the four houses was recorded for three con-
secutive flocks. Locations were estimated using printed numbers placed at 10-ft increments lengthwise along the north wall of each house and known locations of walls, feed lines, water lines, and roof ridge line across the houses. By using these reference points, each dead bird could be recorded to the nearest 1 ft on an X-Y coordinate system. Dead birds were collected twice daily with all data recorded and later transferred to a spreadsheet for analysis. Data were analyzed using scatter diagrams, frequency distributions, and analyses of variance. Scatter diagrams were initially used to analyze the data. Lengthwise locations were plotted on the X-axis and crosswise locations on the Y-axis. These diagrams gave preliminary indications of mortality patterns and guided further analyses. During the second stage of analysis, frequency distributions were plotted for locations in 2-ft increments widthwise and 20-ft increments lengthwise. Major trends in the locations of mortality were evident from these distributions. Finally, lengthwise and widthwise mortalities were transformed by adding 1 to the counts, taking the square roots, and testing separately in analyses of variance with the independent factors of flock, house, and location.
RESULTS AND DISCUSSION Overall mortalities for Flocks 9, 10, and 11 were 7.81, 7.68, and 7.53%, respectively. These mortality levels were typical of other 1992 flocks and indicated that little of the mortality in the ninth (summer) flock was associated with high temperatures or heat stress. The scatter diagram in Figure 1 indicates the halfhouse mortality pattern obtained during the 14d brooding period and is representative of every house (cross- and tunnel-ventilated) for each of the flocks studied. Two distinct rows of heavy mortality concentrations were located at the 10- and 30-ft locations across the house, which exactly coincided with the locations of the feed and water lines. This result simply indicates that the young chicks spent most of their time near feed and water, with subsequent higher concentrations of mortality at these locations. Except for noting the early half-house mortality above, the remainder of the analyses was
Downloaded from http://japr.oxfordjournals.org/ at East Tennessee State University on June 26, 2015
The environmental conditions and management practices for all houses were identical when possible and conformed to 1992 integrator guidelines. However, for Flock 9 in the summer of 1992, due to differences in house cooling capabilities, unavoidable differing environmental conditions occurred. Newly hatched chicks were delivered to all four houses on the same day, but chicks were not always from the same breeder flock or hatchery. Therefore, differences in chick quality and initial mortality were inevitable. Bedding material consisted of a mixture of rice hulls and pine shavings, which were added after a total litter cleanout in the spring of 1992. The three flocks in this study were the second, third, and fourth flocks grown on the same litter. Feed was provided by two lines of pantype feeders placed 10 ft from the north and south sides of the houses. Two lines of nipple waterers were located 3 ft on either side of each feed line. Chicks were half-house brooded for the first 13 to 14 d, during which time feed was provided ad libitum. In addition to the feed pans, 150 plastic feed trays (75 for each feed line used in conjunction with feeder drop tubes) were provided during the half-house brooding stage. After this period, the feed trays were removed, and the birds were released into the whole house and placed on a mealtime feeding program that consisted of six meals per day, with each meal and between-meal interval lasting 2 h. Incandescent light was provided at 0.9 footcandles at bird level. The lighting program consisted of continuous light the first week, natural photoperiod only during the second week, and alternating 2-h periods of night light thereafter until harvest. During the final 6 wk of growth, 2-h night lighting periods corresponded to night-time feeding periods.
JAPR: Research Report
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performed on birds older than 5 wk. Even though mortality varied somewhat with age (brooding vs. growout), Figures 2 to 6 and Tables 1 to 2 are based on all mortality beyond 5 wk of age because of the greater financial losses to growers and integrators represented by such deaths.
An example of the mortality distribution during the final 3 wk of growth in a crossventilated house is illustrated in Figure 2. This pattern is representative of both cross-ventilated houses for each of the three flocks monitored. Although the distribution was more random than during the 14-d brooding period, dis-
FIGURE 2. Spatial distribution of dead chickens during the last 3 wk of growth for Flock 9 in a cross-ventilated house.
Downloaded from http://japr.oxfordjournals.org/ at East Tennessee State University on June 26, 2015
FIGURE 1. Spatial distribution of dead chickens during the 2-wk brooding period for Flock 9 in a cross-ventilated house. The feed lines were located at the 10- and 30-ft south-north coordinates, respectively.
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tinct patterns do appear. More noticeable concentrations of mortality occurred along the sidewalls of the house and at the centerline of the house. Initially, the center concentrations
were thought to be a result of errors in judging the lateral distance; however, they were consistently observed during the later flocks when conscious efforts were made to avoid a center-
FIGURE 4. Three-flock average of crosswise distribution density of dead chickens in a cross-ventilated house during the last 3 wk of growth.
Downloaded from http://japr.oxfordjournals.org/ at East Tennessee State University on June 26, 2015
FIGURE 3. Spatial distribution of dead chickens during the last 3 wk of growth for Flock 9 in a tunnel-ventilated house. (Two 100-ft sections of cooling pad were located in the south sidewall, one starting at the west end of the building and the other starting 160 ft from the west end.)
TABLER ET AL: DEATH LOSS IN BROILER FLOCKS
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line bias. Less noticeable concentrations are also evident at the 10- and 30-ft locations across the house, which again correspond to locations of feed and water.
The mortality distribution pattern for the final 3 wk of Flock 9 in a tunnel-ventilated house is shown in Figure 3. This pattern is representative of both tunnel-ventilated houses
FIGURE 6. Three-flock average of lengthwise distribution density of dead chickens in a tunnel-ventilated house during the last 3 wk of growth.
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FIGURE 5. Three flock average of lengthwise distribution density of dead chickens in a cross-ventilated house during the last 3 wk of growth.
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TABLE 1. Analysis of variance of crosswise distribution of mortality of broilers from 5 wk to harvest Source
SSA
1 2 3 6 19 57 38 114 240
6,071.61 131.74 51.78 191.20 406.02 29.58 38.28 58.75 6,978.96
MS
F
21.3696 0.5189 1.0075 0.5153
41.463** 1.006 1.954*
A SS = sum of squares; MS = mean square; F = estimated value of the F-statistic. *P < 0.05. **P < 0.001.
throughout the 1992 study with three flocks. This pattern of mortality is quite similar to the one observed in the cross-ventilated house, except that more mortalities appeared to occur in front of the two 100-ft sections of evaporative cooling pads and air inlets. Figure 4 shows the average crosswise mortality density in one of the cross-ventilated houses for the final 3 wk of all three flocks. This crosswise density pattern is representative of the cross- and tunnel-ventilated houses during the 1992 study. For all three flocks, more mortality occurred at the sidewalls and at the centerline of the houses. A slight concentration of mortality at the 11 and 31 ft (near locations of feed and water lines) is also noted.
Figure 5 shows the three-flock average lengthwise mortality density for the same cross-ventilated house. The only lengthwise peak of mortality occurred at 50 ft from the west end of the house. Both of the tunnelventilated houses had much more lengthwise variation in mortality. As indicated in Figure 6, high concentrations of mortality occurred at the 0-to-80-, 150-to-220-, and 380-to-400-ft locations. The first two concentrations generally corresponded to the 100-ft sections of fresh air inlets and cooling pads along the south wall. However, study of the scatter diagram in Figure 3 indicates the mortality concentrations occurred along the north sidewall as well as along the south sidewall in front of the inlets. The
TABLE 2. Analysis of variance of lengthwise distribution of mortality of broilers from 5 wk to harvest Source Mean Flock (F) House (H) F×H Location (L) H×L Ven.B × L INS.C × L V×I×L F×L F×H×L Total
df
SSA
1 2 3 6 19 57 19 19 19 38 114 240
6,480.80 118.86 53.26 213.32 35.24 31.92 13.23 9.11 9.57 13.54 32.02 6,978.96
MS
F
1.8547 0.5600 0.6966 0.4795 0.5040 0.3565 0.2809
6.601** 1.993** 2.479* 1.707 1.794 1.269
SS = sum of squares; MS = mean square; F = estimated value of the F-statistic. Two cross-ventilated and two tunnel-ventilated houses. C Two wood tress and two steel tress houses with ceiling insulation R-values of 19 and 10, respectively. Each house type used both ventilation systems. *P < 0.01. **P < 0.001. A B
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Mean Flock (F) House (H) F×H Location (L) H×L F×L F×H×L Total
df
TABLER ET AL: DEATH LOSS IN BROILER FLOCKS
wall, but no noticeable differences in mortality were observed along the north wall. The concentrations of mortality along the pad-and-inlet and exhaust-fan sections of the tunnel-ventilated houses are thought to be a result of birds seeking out or having a preference for those darkened areas. The inlet areas would generally have higher quality air, but temperature and relative humidity might have been more variable. Regardless, a higher concentration of chickens was often observed in the darker areas of the houses during daylight hours. Another behavioral aspect that might have affected the locations of dead birds was an apparent preference by birds in all houses for resting places adjacent to higher objects or surfaces. Older birds tended to seek out the 8-in. concrete footings in the steel frame houses, as these provided a higher and preferred place to rest. A partial explanation to the concentration of mortalities near the centerlines of the houses might have been the placement of instruments (total volume of about 1 ft3) at the 50, 150, 250, and 350 ft along the centerline of each house. The instruments were suspended about five feet from the floor on a PVC pipe that extended to the floor, and those sites were often focal points for resting birds. Slight concentrations near these locations can be observed by close examination of Figures 2 and 3. The above observations refer to birds that were apparently healthy. Poultry managers have often noted that ailing chickens can be seen resting in locations protected from other birds, such as under feed pans and in building corners. In the houses of this study, the sidewalls and the centerlines would be the most isolated from areas of high bird activity near feeders and waterers.
CONCLUSIONS AND APPLICATIONS Results of spatial distribution of broiler mortality for three flocks in four production-scale houses during 1992 revealed the following. 1. Dead birds were concentrated along sidewalls and darkened areas of the houses during later growth periods when mortality represented a major economic loss. 2. Neither the cross-ventilation system nor the tunnel-ventilation system was shown to have a proven advantage over the other in bird mortality. 3. Bird behavior and the psychological mechanisms responsible for such behavior seemed to have the dominant role in determining mortality patterns.
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third concentration occurred in the east end of the house where light and natural ventilation were obstructed by the tunnel exhaust fans. The analyses of variation on mortality from 5 wk to harvest (Tables 1 and 2) tend to support the significance of the above observations. In these analyses, flock, house, and flock-house variations were anticipated and treated as blocks in the design. Location, in 20 equal increments, and its interactions were used as treatment and error estimates. Variation in mortality at the crosswise locations was highly significant, as indicated by Figure 4. The lack of significance in the house × location interaction suggested that the tendency of the chickens to die near the sides and midlines was similar in all houses, regardless of the ventilation style. The analysis of the lengthwise mortality distributions in Table 2 also showed that location was a highly significant factor. In contrast to Table 1, the house × location interaction was highly significant. This resulted in separation of the ventilation and insulation interactions and indicated that the two ventilation systems had a significant effect on the mortality location. This difference was assumed to result from the accumulations of dead birds in the pad-and-inlet and exhaust fan sections of the tunnel-ventilated houses. Consideration of all the experimental results suggested that bird behavior was the dominant factor in determining the location of mortality. Earlier conjecture that perhaps more mortality occurred in poorly ventilated house sections was not confirmed by the experimental data. More dead birds were found along the sidewalls with either type of ventilation system. In this study, the cross-ventilated houses may have had “dead-air” spots along the north
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4. Environmental variations in temperature, relative humidity, and wind speed (although not documented) did not seem to directly determine mortality patterns; however, these variations might have affected bird behavior to indirectly establish distinctive mortality patterns.
REFERENCES AND NOTES
2. Julian, R. J. 1987. The effect of increased sodium in the drinking water on right ventricular hypertrophy, right ventricular failure, and ascites in broiler chickens. Avian Pathol. 16:61–71. 3. Hoeer, F. J. 1988. Pathogenesis of ascites. Poult. Dig. 47:8–12. 4. Shane, S. M. 1988. Understanding ascites. Indian River Breeder Update IV(2):1–6.
7. Brigden, J. L., and C. Riddell. 1975. A survey of mortality in four broiler flocks in western Canada. Can. Vet. J. 16:194–200. 8. Riddell, C., and J. P. Orr. 1980. Chemical studies of blood, and histological studies of the heart of broiler chickens dying from acute death syndrome. Avian Dis. 29:90–102. 9. Steele, P., and J. Edgar. 1982. Importance of acute death syndrome in mortalities in broiler flocks. Aust. Vet. J. 58:63–66. 10. Xin, H., I. L. Berry, T. L. Barton, and G. T. Tabler. 1994. Feed and water consumption, growth, and mortality of male broilers. Poult. Sci. 73:610–616.
5. Wideman, R. F. 1988. Ascites in poultry. Monsanto Nutr. Update 6(2):1–7.
11. Berry, I. L., R. C. Benz, and H. Xin. 1991. A controller for combining natural and mechanical ventilation of broilers. ASAE Technical Paper No. 914038. ASAE, St. Joseph, MI.
6. Volk, M., M. Herceg, B. Marzan, M. Kralj, S. Meknic, and V. Tadic. 1974. Investigations of fatal syncope in broiler chickens. 1. Frequency of occurrence, clinical symptoms, pathomorphological findings and pathogenesis. Vet. Arhiv 44:14–23.
12. Xin, H., I. L. Berry, T. L. Barton, and G. T. Tabler. 1994. Temperature and humidity profiles of broiler houses with experimental conventional and tunnel ventilation systems. Appl. Eng. Agric. 10:535–542.
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1. Anderson, L. S., M. Gleeson, A. L. Haigh, and V. Molong. 1986. Respiratory responses of the domestic fowl to low level carbon dioxide exposure. Res. Vet. Sci. 40:99–104.
Spatial Distribution of Death Losses in Broiler Flocks G. T. Tabler,*,1 I. L. Berry,† H. Xin,† and T. L. Barton§
Primary Audience: Flock Supervisors, Growers, Integrators SUMMARY Mortality in poultry flocks continues to be a major economic loss to broiler growers and integrators. Also, disposal of dead chickens in an environmentally safe manner is becoming increasingly demanding. Accurate descriptions of mortality patterns within broiler houses may prove beneficial with respect to an overall management strategy to minimize death losses during flock growouts. To characterize mortality patterns, locations of dead chickens in four productionscale broiler houses with an east-west orientation were monitored during a 6-mo period in 1992 covering three consecutive flocks in northwest Arkansas. Overall mortality was not affected by the two different ventilation systems used (i.e., conventional cross ventilation with mist cooling in summer vs. tunnel ventilation with pad cooling in summer). Higher mortalities were observed along the north and south sidewalls and centerlines of the houses (e.g., under measurement instruments) and in areas where natural lighting was obstructed (e.g., behind ventilation fans and cooling pads). Key words: broiler, broiler house, conventional ventilation, death location, mortality, tunnel ventilation 2002 J. Appl. Poult. Res. 11:388–396
DESCRIPTION OF PROBLEM Mortality of birds in poultry production facilities represents a major economic loss for poultry producers and the integrators who usually own the birds. Not only do these dead birds represent lost income, they also represent a disposal problem that must be addressed in an environmentally friendly way. Disposal of dead birds becomes an even larger issue for producers each year as more attention is focused on the environment. Further, poultry production continues to increase in areas already 1
crowded with production facilities, and in many instances people are moving into the same areas and suddenly find themselves neighbors with existing production facilities. Mortality at broiler operations can result from a variety of causes. The most predominant causes during the 1992 research period were ascites, sudden death syndrome (SDS), leg problems, and heat prostration. Today, with improved genetics that have somewhat alleviated ascites, leg problems are perhaps a greater area of concern with broilers being held for
To whom correspondence should be addressed: [email protected].
Downloaded from http://japr.oxfordjournals.org/ at East Tennessee State University on June 26, 2015
*Department of Poultry Science, University of Arkansas, Fayetteville, Arkansas 72701; †Department of Biological and Agricultural Engineering, University of Arkansas, Fayetteville, Arkansas 72701; ‡Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, Iowa 50011; and §Department of Poultry Science, Cooperative Extension Service, University of Arkansas, Fayetteville, Arkansas 72701
TABLER ET AL: DEATH LOSS IN BROILER FLOCKS
in younger birds. This leads to the consideration of mortality patterns as a possible means of evaluating localized environments within broiler houses. Most growers and flock supervisors are aware that many dead chickens will be concentrated in certain locations, such as along sidewalls and perhaps near the ends of houses. However, the exact causes of these patterns remains somewhat of a mystery. Do the concentrations result from increased numbers of deaths due to poorer environments in those same areas? Do the concentrations simply result from greater numbers of birds that inhabit a certain area or a greater proportion of time spent in some areas vs. others? Do ailing birds prefer different areas than healthy birds? In response to the questions above, the objectives of this research were to 1) determine and describe spatial distribution of mortality that occurred in typical 1992 broiler growing environments and 2) determine if mortality distribution patterns were associated with environmental variations.
MATERIALS AND METHODS To accurately assess mortality distribution patterns, the location of each dead chicken was recorded daily for three consecutive flocks of 75,200 birds each, from June to December 1992. The birds were the ninth, tenth, and eleventh flocks grown in four commercial-scale broiler houses constructed in 1990, operated by the University of Arkansas and located 12 miles west of Fayetteville, Arkansas, for the purpose of studying energy-efficiency-related to broiler production. Broilers were grown under a standard 1992 industry production contract with a local integrator, who recommended broiler management practices for the flocks. Broiler Houses The four broiler houses were each 40 ft (12.2 m) wide by 400 ft (122 m) long and were equipped with temporary partitions at the lengthwise center for half-house brooding of young chicks. Two houses were constructed with cross-ventilation cooling fans located diagonally along the south wall and low-pressure (120 psi) foggers. The other two houses had
Downloaded from http://japr.oxfordjournals.org/ at East Tennessee State University on June 26, 2015
longer growout periods to reach heavier weights. Heat prostration and SDS continue to be major issues facing the industry. Ascites refers to the accumulation of edematous fluid within the body cavity. Several situations influence its occurrence in broilers: 1) atmospheric hypoxia, 2) housing environment, 3) respiratory diseases, 4) rapid growth rates, 5) high energy diets, 6) toxins, 7) pellets vs. mash, 8) ad libitum vs. restricted feeding, and 9) feed additives such as NaCl [1, 2, 3, 4, 5]. Sudden death syndrome (SDS) is reported as a major cause of death in broiler flocks in many countries around the world [6, 7, 8, 9]. Attempts to cure the disease have, largely, proved unsuccessful. Mortality resulting from heat stress continues to be a problem during hot weather. Increased stocking density and genetic emphasis on faster growth rates along with increased breast meat yield and heavier harvest weights further exacerbate heat-related problems. Reduced feed intake, depressed rates of gain, and increased mortality rates often result when broilers are subjected to high summer temperatures, particularly near the end of the growout cycle. Heat-related mortality has decreased somewhat because of increased insulation and advanced cooling systems (e.g., foggers, misters, evaporative cooling pads) in contemporary production facilities. In addition to the above-mentioned causes of broiler mortality, several other factors may also influence mortality rates. Genetics, sex of bird, health and immune status of breeder flock and hatchery sanitation, longer growout periods, and degree of on-farm culling may all affect mortality within a normal range when acute mortality does not result from temperature stress or disease. Average mortality of male broilers in four production-scale houses over 10 8-wk growth periods was 6.8% [10]. With 6-wk growing periods, mortality can be 4% or less. The increasing production of heavy broilers (8-wk or longer growout periods) for deboning and further processing markets has increased the need for more sophisticated environmental systems in broiler housing. Part of this need results from increased mortality occurring after 6 wk, which represents a much greater financial loss to growers and integrators than mortality
389
390 tunnel ventilation with static pressure-controlled air inlets and evaporative cooling pads. A detailed description of the houses and the environmental control systems was given by Berry et al. [11] and Xin et al. [12]. Flock Management
Data Collection and Analyses The location of each dead chicken in each of the four houses was recorded for three con-
secutive flocks. Locations were estimated using printed numbers placed at 10-ft increments lengthwise along the north wall of each house and known locations of walls, feed lines, water lines, and roof ridge line across the houses. By using these reference points, each dead bird could be recorded to the nearest 1 ft on an X-Y coordinate system. Dead birds were collected twice daily with all data recorded and later transferred to a spreadsheet for analysis. Data were analyzed using scatter diagrams, frequency distributions, and analyses of variance. Scatter diagrams were initially used to analyze the data. Lengthwise locations were plotted on the X-axis and crosswise locations on the Y-axis. These diagrams gave preliminary indications of mortality patterns and guided further analyses. During the second stage of analysis, frequency distributions were plotted for locations in 2-ft increments widthwise and 20-ft increments lengthwise. Major trends in the locations of mortality were evident from these distributions. Finally, lengthwise and widthwise mortalities were transformed by adding 1 to the counts, taking the square roots, and testing separately in analyses of variance with the independent factors of flock, house, and location.
RESULTS AND DISCUSSION Overall mortalities for Flocks 9, 10, and 11 were 7.81, 7.68, and 7.53%, respectively. These mortality levels were typical of other 1992 flocks and indicated that little of the mortality in the ninth (summer) flock was associated with high temperatures or heat stress. The scatter diagram in Figure 1 indicates the halfhouse mortality pattern obtained during the 14d brooding period and is representative of every house (cross- and tunnel-ventilated) for each of the flocks studied. Two distinct rows of heavy mortality concentrations were located at the 10- and 30-ft locations across the house, which exactly coincided with the locations of the feed and water lines. This result simply indicates that the young chicks spent most of their time near feed and water, with subsequent higher concentrations of mortality at these locations. Except for noting the early half-house mortality above, the remainder of the analyses was
Downloaded from http://japr.oxfordjournals.org/ at East Tennessee State University on June 26, 2015
The environmental conditions and management practices for all houses were identical when possible and conformed to 1992 integrator guidelines. However, for Flock 9 in the summer of 1992, due to differences in house cooling capabilities, unavoidable differing environmental conditions occurred. Newly hatched chicks were delivered to all four houses on the same day, but chicks were not always from the same breeder flock or hatchery. Therefore, differences in chick quality and initial mortality were inevitable. Bedding material consisted of a mixture of rice hulls and pine shavings, which were added after a total litter cleanout in the spring of 1992. The three flocks in this study were the second, third, and fourth flocks grown on the same litter. Feed was provided by two lines of pantype feeders placed 10 ft from the north and south sides of the houses. Two lines of nipple waterers were located 3 ft on either side of each feed line. Chicks were half-house brooded for the first 13 to 14 d, during which time feed was provided ad libitum. In addition to the feed pans, 150 plastic feed trays (75 for each feed line used in conjunction with feeder drop tubes) were provided during the half-house brooding stage. After this period, the feed trays were removed, and the birds were released into the whole house and placed on a mealtime feeding program that consisted of six meals per day, with each meal and between-meal interval lasting 2 h. Incandescent light was provided at 0.9 footcandles at bird level. The lighting program consisted of continuous light the first week, natural photoperiod only during the second week, and alternating 2-h periods of night light thereafter until harvest. During the final 6 wk of growth, 2-h night lighting periods corresponded to night-time feeding periods.
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performed on birds older than 5 wk. Even though mortality varied somewhat with age (brooding vs. growout), Figures 2 to 6 and Tables 1 to 2 are based on all mortality beyond 5 wk of age because of the greater financial losses to growers and integrators represented by such deaths.
An example of the mortality distribution during the final 3 wk of growth in a crossventilated house is illustrated in Figure 2. This pattern is representative of both cross-ventilated houses for each of the three flocks monitored. Although the distribution was more random than during the 14-d brooding period, dis-
FIGURE 2. Spatial distribution of dead chickens during the last 3 wk of growth for Flock 9 in a cross-ventilated house.
Downloaded from http://japr.oxfordjournals.org/ at East Tennessee State University on June 26, 2015
FIGURE 1. Spatial distribution of dead chickens during the 2-wk brooding period for Flock 9 in a cross-ventilated house. The feed lines were located at the 10- and 30-ft south-north coordinates, respectively.
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tinct patterns do appear. More noticeable concentrations of mortality occurred along the sidewalls of the house and at the centerline of the house. Initially, the center concentrations
were thought to be a result of errors in judging the lateral distance; however, they were consistently observed during the later flocks when conscious efforts were made to avoid a center-
FIGURE 4. Three-flock average of crosswise distribution density of dead chickens in a cross-ventilated house during the last 3 wk of growth.
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FIGURE 3. Spatial distribution of dead chickens during the last 3 wk of growth for Flock 9 in a tunnel-ventilated house. (Two 100-ft sections of cooling pad were located in the south sidewall, one starting at the west end of the building and the other starting 160 ft from the west end.)
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line bias. Less noticeable concentrations are also evident at the 10- and 30-ft locations across the house, which again correspond to locations of feed and water.
The mortality distribution pattern for the final 3 wk of Flock 9 in a tunnel-ventilated house is shown in Figure 3. This pattern is representative of both tunnel-ventilated houses
FIGURE 6. Three-flock average of lengthwise distribution density of dead chickens in a tunnel-ventilated house during the last 3 wk of growth.
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FIGURE 5. Three flock average of lengthwise distribution density of dead chickens in a cross-ventilated house during the last 3 wk of growth.
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TABLE 1. Analysis of variance of crosswise distribution of mortality of broilers from 5 wk to harvest Source
SSA
1 2 3 6 19 57 38 114 240
6,071.61 131.74 51.78 191.20 406.02 29.58 38.28 58.75 6,978.96
MS
F
21.3696 0.5189 1.0075 0.5153
41.463** 1.006 1.954*
A SS = sum of squares; MS = mean square; F = estimated value of the F-statistic. *P < 0.05. **P < 0.001.
throughout the 1992 study with three flocks. This pattern of mortality is quite similar to the one observed in the cross-ventilated house, except that more mortalities appeared to occur in front of the two 100-ft sections of evaporative cooling pads and air inlets. Figure 4 shows the average crosswise mortality density in one of the cross-ventilated houses for the final 3 wk of all three flocks. This crosswise density pattern is representative of the cross- and tunnel-ventilated houses during the 1992 study. For all three flocks, more mortality occurred at the sidewalls and at the centerline of the houses. A slight concentration of mortality at the 11 and 31 ft (near locations of feed and water lines) is also noted.
Figure 5 shows the three-flock average lengthwise mortality density for the same cross-ventilated house. The only lengthwise peak of mortality occurred at 50 ft from the west end of the house. Both of the tunnelventilated houses had much more lengthwise variation in mortality. As indicated in Figure 6, high concentrations of mortality occurred at the 0-to-80-, 150-to-220-, and 380-to-400-ft locations. The first two concentrations generally corresponded to the 100-ft sections of fresh air inlets and cooling pads along the south wall. However, study of the scatter diagram in Figure 3 indicates the mortality concentrations occurred along the north sidewall as well as along the south sidewall in front of the inlets. The
TABLE 2. Analysis of variance of lengthwise distribution of mortality of broilers from 5 wk to harvest Source Mean Flock (F) House (H) F×H Location (L) H×L Ven.B × L INS.C × L V×I×L F×L F×H×L Total
df
SSA
1 2 3 6 19 57 19 19 19 38 114 240
6,480.80 118.86 53.26 213.32 35.24 31.92 13.23 9.11 9.57 13.54 32.02 6,978.96
MS
F
1.8547 0.5600 0.6966 0.4795 0.5040 0.3565 0.2809
6.601** 1.993** 2.479* 1.707 1.794 1.269
SS = sum of squares; MS = mean square; F = estimated value of the F-statistic. Two cross-ventilated and two tunnel-ventilated houses. C Two wood tress and two steel tress houses with ceiling insulation R-values of 19 and 10, respectively. Each house type used both ventilation systems. *P < 0.01. **P < 0.001. A B
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Mean Flock (F) House (H) F×H Location (L) H×L F×L F×H×L Total
df
TABLER ET AL: DEATH LOSS IN BROILER FLOCKS
wall, but no noticeable differences in mortality were observed along the north wall. The concentrations of mortality along the pad-and-inlet and exhaust-fan sections of the tunnel-ventilated houses are thought to be a result of birds seeking out or having a preference for those darkened areas. The inlet areas would generally have higher quality air, but temperature and relative humidity might have been more variable. Regardless, a higher concentration of chickens was often observed in the darker areas of the houses during daylight hours. Another behavioral aspect that might have affected the locations of dead birds was an apparent preference by birds in all houses for resting places adjacent to higher objects or surfaces. Older birds tended to seek out the 8-in. concrete footings in the steel frame houses, as these provided a higher and preferred place to rest. A partial explanation to the concentration of mortalities near the centerlines of the houses might have been the placement of instruments (total volume of about 1 ft3) at the 50, 150, 250, and 350 ft along the centerline of each house. The instruments were suspended about five feet from the floor on a PVC pipe that extended to the floor, and those sites were often focal points for resting birds. Slight concentrations near these locations can be observed by close examination of Figures 2 and 3. The above observations refer to birds that were apparently healthy. Poultry managers have often noted that ailing chickens can be seen resting in locations protected from other birds, such as under feed pans and in building corners. In the houses of this study, the sidewalls and the centerlines would be the most isolated from areas of high bird activity near feeders and waterers.
CONCLUSIONS AND APPLICATIONS Results of spatial distribution of broiler mortality for three flocks in four production-scale houses during 1992 revealed the following. 1. Dead birds were concentrated along sidewalls and darkened areas of the houses during later growth periods when mortality represented a major economic loss. 2. Neither the cross-ventilation system nor the tunnel-ventilation system was shown to have a proven advantage over the other in bird mortality. 3. Bird behavior and the psychological mechanisms responsible for such behavior seemed to have the dominant role in determining mortality patterns.
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third concentration occurred in the east end of the house where light and natural ventilation were obstructed by the tunnel exhaust fans. The analyses of variation on mortality from 5 wk to harvest (Tables 1 and 2) tend to support the significance of the above observations. In these analyses, flock, house, and flock-house variations were anticipated and treated as blocks in the design. Location, in 20 equal increments, and its interactions were used as treatment and error estimates. Variation in mortality at the crosswise locations was highly significant, as indicated by Figure 4. The lack of significance in the house × location interaction suggested that the tendency of the chickens to die near the sides and midlines was similar in all houses, regardless of the ventilation style. The analysis of the lengthwise mortality distributions in Table 2 also showed that location was a highly significant factor. In contrast to Table 1, the house × location interaction was highly significant. This resulted in separation of the ventilation and insulation interactions and indicated that the two ventilation systems had a significant effect on the mortality location. This difference was assumed to result from the accumulations of dead birds in the pad-and-inlet and exhaust fan sections of the tunnel-ventilated houses. Consideration of all the experimental results suggested that bird behavior was the dominant factor in determining the location of mortality. Earlier conjecture that perhaps more mortality occurred in poorly ventilated house sections was not confirmed by the experimental data. More dead birds were found along the sidewalls with either type of ventilation system. In this study, the cross-ventilated houses may have had “dead-air” spots along the north
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4. Environmental variations in temperature, relative humidity, and wind speed (although not documented) did not seem to directly determine mortality patterns; however, these variations might have affected bird behavior to indirectly establish distinctive mortality patterns.
REFERENCES AND NOTES
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