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1. LRH: R. Monleon et al.
RRH: Mortality in two commercial turkey strains
Causes of Mortality in Two Commercial Turkey Strains
Raised Concurrently Under Simulated Commercial Conditions
R. Monleon, M. Alfonso, J. S. Guy, D. Wages, and H. J. BarnesA
Poultry Health Management, Department of Population Health & Pathobiology, College
of Veterinary Medicine, North Carolina State University,
4700 Hillsborough St., Raleigh, NC 27606, U.S.A.
For submission to: Avian Diseases
A
Corresponding Author. Dr. H. John Barnes, Poultry Health Management, Department
of Population Health & Pathobiology, College of Veterinary Medicine, North Carolina
State University, 4700 Hillsborough Street, Raleigh, NC 27606.
Tel: (919) 513-6273. Fax: (919) 513-6383. Email: john_barnes@ncsu.edu

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SUMMARY. Patterns and causes of mortality were determined for two commercial
turkey strains (StL, n =998; StR, n =1005) raised together under simulated commercial
conditions. All parameters (incubation, transport, etc.) were identical except for breeder
flock age, which was 40 wks for StL and 53 wks for StR. Brooding and growout were
done according to the Integrator’s guidelines. All combined (StL and StR) mortality
(9.6%) was necropsied to determine the most probable cause of death or reason for
culling. Total StR mortality was 3.3% higher than StL mortality, and the patterns and
causes thereof differed in comparison with previous studies. Significant differences (p =
< 0.05) in causes of mortality between strains were observed for yolk sac infection: StR
(7.4%) vs. StL (2.4%), and for spontaneous cardiomyopathy: StL (2.6%) vs. StR (0.9%).
Other causes of mortality did not significantly differ between the two strains.
RESUMEN. Los patrones y las causas de mortalidad fueron determinados en dos estirpes
comerciales distintas de pavos (StL, n =998; StR, n =1005) que fueron criados juntos
bajo condiciones comerciales simuladas. Todos los parametros (incubacion, transporte,
etc) fueron iguales excepto la edad de los reproductores , que era 40 semanas para StL y
53 semanas para StR, todos los demas parametros eran identicos. La crianza se hizo de
acorde a las guias del Intergrador. Al total de la mortalidad (StL y StR) (9.6%) le fue
practicada necropsia, y se determino la causa mas probable de muerte o razon de
descarte. La mortalidad en StR fue un 3.3% mas alta que en StL. Los patrones y las
causas de mortalidad difirieron en comparacion con estudios previos. Diferencias
significativas fueron observadas en las causas de mortalidad entre estirpes en O/P/S: StR
(7.4%) contra StL (2.4%) y en cardiomiopatia espontanea: StL (2.6%) contra StR (0.9%).
Otras causas de mortalidad no difirieron significativamente entre las dos estirpes.

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Keywords: turkey, mortality, spontaneous cardiomyopathy, omphalitis.
Abbreviations: MD=Musculoskeletal diseases, O/P/S=Omphalitis/Peritonitis/Septicemia,
SC=Spontaneous cardiomyopathy, SO=Starve-out, StL=Strain L, StR=Strain R.

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In 2004, 264 million turkeys with an average weight of 12.3 kg were raised in the
USA at an average price of $0.92 per kg, and with 10.4% average loss due to mortality
(8, 9). Determining the etiology of mortality in turkey flocks would be the first step in
initiating a comprehensive health plan. Limited accurate information is available that
summarizes data regarding incidence and prevalence of the various diseases affecting
commercial turkeys and contributing to mortality. As these mortality losses substantially
decrease profits in the poultry industry, recognizing the underlying causes of high
mortality can lead to improved flock management which can then be translated into
increased revenue.
It has been reported in a study of 38 consecutive flocks of broiler chickens (16)
that peak mortality occurs between days 3-4 with a subsequent decrease until day 10,
followed by a pause, then a gradual increase from day 30 until processing. Xin et al. (16)
also demonstrated a similar pattern in a different study. To date, no related studies
regarding patterns of mortality have been conducted with commercial meat turkeys.
However, a report from the Iowa State University Extension (11) describes data
on health problems from a 12-year survey mailed directly to Iowa meat-type turkey
growers between 1983 and 1994, comprising a total number of flocks ranging from 118
to 441 per year, with an average flock size of 10,700 turkeys. The survey covered
numerous aspects of turkey health, including questions regarding specific causes of
health problems and the resulting mortality percentage from those specific problems.
Colibacillosis was the most serious health problem, affecting 30.2% of all flocks with an
average mortality of 3.9%, followed by leg problems (16.3% / 5.1%) and dissecting
aneurysm (14.4% / 1.3%).

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In another recent study conducted with 35,706 meat-type turkeys submitted to the
Fresno and Turlock branches of the California Animal Health and Food Safety
Laboratory System between 1989 and 2001, Shivaprasad et al. (15) reported
colibacillosis (2678 [16.7%]), poult enteritis syndrome (1857 [11.6%]), and turkey coryza
(B. avium) (1119 [7.0%]) as the three major identified diseases. Notwithstanding these
results, the study suggested that data may not have represented all the mortality
conditions seen in the farms, as it was based on submissions to the diagnostic laboratory.
The specific objective of the study described here was to determine the causes of
mortality in two commercial turkey strains raised together under simulated commercial
conditions in order to provide a better understanding of mortality and to improve the
current knowledge of patterns and causes of mortality. Additionally, a comparison of
patterns of mortality reported by Tabler et al. (16) with our data was done to determine if
their findings could be extrapolated to turkey flocks.
MATERIALS AND METHODS
Case materials. This study was conducted between August 2004 and November
2004. Two thousand and three female poults comprised of approximately equal numbers
of two different primary breeder strains, Strain L (n=998) and Strain R (n=1005), were
obtained on the day of hatch from a turkey integrator in North Carolina. Strains were
identified by different conditioning patterns of the first toe: the left toe was amputated on
Strain L (StL) poults while the right toe was amputated on Strain R (StR) poults. All
poults received infrared beak conditioning as well as microwave conditioning of toes 2,
3, and 4. StL poults came from a 40 week-old breeder flock, whereas StR poults came

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from breeder hens that were 53 weeks old. Fifty turkeys were weighed weekly by strain
until week 3 and 30 by strain weekly thereafter. Data was recorded to obtain weekly
average body weight and other statistical parameters.
Housing. Turkeys were co-mingled and raised together in a 12.1 m x 42.7 m
cross-ventilated, curtain-sided, commercial-style poultry house with automatic feeding
and watering systems located at the Teaching Animal Unit at the College of Veterinary
Medicine, North Carolina State University in Raleigh until they were removed at 81d of
age for processing. Both strains were processed concurrently as it was not practical to
separate them prior to their removal. Fresh pine shavings were used for bedding. Litter
(mixture of bedding and turkey droppings) was removed from the house between flocks
with no recycling. Ventilation was provided by three 122 cm diameter enhanced side-
wall cooling fans located on the south side and overhead rotatory fans. Light was
provided for 24 hrs the first day, 23 hours until day 14, 20 hours until day 21, 18 hours
until day 28, and then 16 hours daily until load-out. Brooding, heating and ventilation
were supplied according to the integrator’s guidelines.
The house was equipped with 2 rows of Plasson®
bell-type drinkers (brooder
drinker space was at 0.9 cm per bird or 125 birds per drinker and finishing drinker space
was at 1.3 cm per bird or 90 birds per drinker), 2 rows of commercial turkey hen pan
feeders (brooder feeder space was at 2.2cm per bird or 50 birds per feed pan and finishing
feeder space was at 5.3 cm per bird or 20 birds per feed pan), and 2 rows of incandescent
light bulbs (12 40W light bulbs per row). Litter, under-drinkers and feeders was raked
daily until week 8. Turkeys were fed commercial feed (Table 1) manufactured and
supplied by the integrator and provided municipal, chlorinated water ad libitum. No

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drugs or vaccines were administered during grow out except for coccidiostats and growth
promoters contained in the integrator’s feed rations, including monensin, virginiamycin,
and bambermycin.
Biosecurity. Measures included the wearing of coveralls and plastic boots, boot
washing with an acid phenolic disinfectant (LpH®
, STERIS Corporation, Mentor, OH
44060), and visitor restriction. The farm is isolated from other commercial poultry
operations, however, a swine farrowing house is located within 50 m, and a flock of free-
living Canada geese (Branta canadensis) resides near the barn. One flock of turkeys is
raised in the barn per year following a flock of commercial broiler chickens. The house
is thoroughly cleaned and disinfected after the removal of each flock and has a downtime
of approximately 4 months between flocks.
Mortality. The turkey flock was examined at least three times per day. Mortality
was gathered at each visit and stored at 4C until examination. Birds unresponsive to
stimuli, lame to the point that they could not readily eat or drink, and those severely
persecuted by other birds in the flock were culled when identified. All birds that died or
were culled were necropsied to determine the most probable cause of death or reason for
culling. Additional diagnostic samples were collected when necessary.
Statistical analysis. Differences in causes of mortality between strains were
analyzed by means of SAS/STAT® software categorical analysis using the general model
(GENMOD) procedure of SAS Institute (13) to determine statistical significance (p = <
0.05) between mortality due to Omphalitis/Peritonitis/Septicemia (O/P/S) in StL and StR,
Spontaneous cardiomyopathy (SC) in StL and StR, Musculoskeletal diseases (MD) in StL
and. StR, and Starve-out (SO) in StL and StR.

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RESULTS
Body weights. Average body weight at 77 days was 6.0 kg for StL and 6.6 kg for
StR. Results were below the breed standard (6.2 kg) for StL and over the breed standard
(6.2 kg.) for StR. Feed Conversion Ratio for the combined (StL and StR) flock was 1.94.
Average combined flock daily weight gain was 82 g per day.
Mortality. Total mortality numbered 193 turkeys (9.6%), of which 158 died and
35 were culled. One-hundred-ninety birds were necropsied (155 that died; 35 that were
culled): three birds that died were accidentally discarded and unavailable for necropsy.
Total mortality from all causes was 11.3% for StR and 8.0% for StL.
Patterns of mortality. 45.6% of total mortality occurred in the first week (Figure
1 and 2). Mortality peaked on day 3 in both strains and subsequently declined until day
15. After the first peak on day 3 there were three additional peaks on days 17, 25, and 31.
Causes of mortality. Combined mortality due to infectious diseases was 5.1%
(StL 2.7%, StR 7.5%); 2.8% (StL 4.7%, StR 3.0%) for non-infectious diseases, and
undetermined for 1.4% (StL 0.6%, StR 0.8%). In the combined flock, O/P/S was the
major cause of mortality, followed by SC, SO, and MD (Table 2). SC was the major
cause of mortality in StL while O/P/S was the major cause of mortality in StR. Other
incidental causes were identified but not statistically significant. Peak mortality on day
17 was attributable to O/P/S in 50% of the 6 cases, on day 25 due to a variety of causes,
and on day 31 mainly due to SC (67%), with 1 case in StR, and 3 in StL.
Statistical analysis. Differences in mortality due to O/P/S and SC were
statistically significant. No statistical significance was found for MD and SO (Table 2).

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DISCUSSION
In this study, we found that the initial mortality peak trend established by Tabler
et al. and Xin et al. (16, 17) in broiler chickens was consistent with our results in turkeys.
We therefore initially considered that those results might be extrapolated as a model for
other turkey flocks. However, in contrast with the results described by Tabler et al. and
Xin et al (16, 17), no incremental trend in mortality during the end of the growing period
was observed in our study despite the three mortality peaks we noted.
According to Tabler and Xin (16, 17), the most common cause of peak mortality
at day three in their study occurred due to exhaustion of yolk sac reserves. In contrast,
during our study O/P/S was the most common cause of death.
Owings (11) reported colibacillosis, leg problems, and dissecting aneurysms as
the three most common health problems claimed by Iowa growers. In our study, none of
those problems were among the three main causes of mortality. Remarkably, we did not
observed any dissecting aneurysms during the evaluated period.
Causes of combined mortality also differed from those reported by Shivaprasad et
al. (15). Cases submitted to the California Animal Health and Food Safety Laboratory
System did not represent the total flock mortality, and an unknown percentage of
mortality was diagnosed on-farm. Therefore it was suggested that the most recognizable
and most common mortality causes may have not been reported nor submitted by the
producers.
Studies in chickens have associated breeder age with bacterial contamination of
the egg and with early mortality due to a decrease in cuticle quality and thinner shell-

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membranes (12). StL poults hatched from the 40-week old breeder flock showed an
incidence of 2.4% of O/P/S while StR poults hatched from a 53-week old breeder flock,
which was discarded for breeding after this lay, had an incidence of 7.4%. Given that all
other incubation and living parameters were the same, the significant difference in O/P/S
incidence was consistent with variable breeder age factors and therefore breeder-flock
related.
SC is a well-described disease in turkeys (1, 2, 3, 7) for which a variety of risk
factors have been associated (1, 3, 4, 5, 6, 7). Owing and Shivaprasad et al. (11, 15)
reported a 1.4% occurrence in their studies, and other authors suggest incidences ranging
from 0.5% to 3%, up through 22% (1, 4). In our study, StL had 2.6% mortality due to SC
and StR had 0.9% mortality. Statistical analysis demonstrated a significant difference
between the 2 groups. Breeder age in relation to shell thickness and hypoxic conditions
has been suggested as a cause of increased SC mortality (1, 6, 10). However, the
significant increase in SC mortality was seen in StL, composed of turkeys in the 40-week
old flock, which is not normally an at-risk age group. All other parameters were identical
for both strains. Therefore, we consider that increased mortality due to SC may be linked
to strain genetics in StL.
Mortality attributed to SO and MD did not differ significantly between strains.
Values obtained differ from the results shown in Owing and Shivaprasad et al. (11, 15)
studies.
The possibility that the observed differences were linked to the specific breeder
flocks and to the strain of turkey cannot be fully determined, as only one breeder flock
producing each strain was examined in this study. Examination of additional flocks of

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each strain produced by different breeder flocks would be needed to make this
determination. However, it is apparent that patterns of mortality and causes of mortality
may be attributed to strain and/or breeder flock factors and that this should be considered
when excess or unusual mortality in commercial turkey flocks is investigated.

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ACKNOWLEDGMENTS
The authors would like to thanks Dr. D. Rives and Mrs. P. Jay for their continuous
assistance, and Drs. O. J. Fletcher, D. H. Ley, and Miss. C. Germain for their editorial
assistance.