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Research article
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Title:
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Dairy cattle mortality in an organized farm in Bangladesh
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Authors:
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M. M. Hossain1, 3*, A. H. M. Kamal1, A. K. M. A. Rahman2, H. S. Cho3
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Department of Medicine, Sylhet Agricultural University, Bangladesh
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Department of Medicine, Bangladesh Agricultural University, Mymensingh
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College of Veterinary Medicine and Bio-safety Research Institute, Chonbuk National University,
Jeonju 561-756, Republic of Korea
*Corresponding Author:
Md. Mukter Hossain DVM, MS, MSc
PhD Student
College of Veterinary Medicine
Chonbuk National University
Jeonju 561-756, South Korea
Phone: +82-63-270-4872 (Office)
Cell:+82-10-8200-5510
Fax:+82-63-270-3780
E-mail: mukter.sau@gmail.com
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Dairy cattle mortality in an organized farm in Bangladesh
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ABSTRACT
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A retrospective study of dairy cattle mortality on the Central Cattle Breeding and Dairy Farm in
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Bangladesh was carried out between 1992 and 2007. Sixteen years of data on mortality of dairy
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cattle were analyzed for the effects of year, season, age, sex, breed, and etiology on mortality
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rate. The average overall mortality rate was 5.60% and on average, female cattle (55.71%) were
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found to die more than males (44.29%). Mortality was significantly higher in exotic and
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crossbred animals than in local/indigenous cattle. There was variation in seasonal mortality rate
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averaging 28.99%, 33.03%, and 37.98% in rainy, summer, and winter seasons, respectively. The
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major causes of death were diseases of the respiratory tract, mainly pneumonia (39.91%).
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Tuberculosis was the second most common cause of mortality accounting for 20.58% of deaths.
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The other major cause of death was disease of the alimentary tract, mainly enteritis (15.58%).
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Other causes of death occurred in the following frequencies: malnutrition (5.91%), debility
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(4.43%), hairball (3.35%), tympanitis (2.56%), babesiosis (2.27%), internal hemorrhage (2.16%),
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black quarter (1.76%), and foot and mouth disease (1.48%). Of the four potential risk factors
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investigated, age was the most important factor and significantly associated with mortality.
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During the first month of life, calves had a higher risk of mortality than adults.
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Key words: Mortality, Cattle, Causes, CCBDF, Bangladesh
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Introduction
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Dairy cattle mortality is a severe problem for the dairy industry. Mortality among dairy cattle
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results in financial loss, including the value of the lost cattle, cost of replacement, loss of milk
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production, and extra labor (Thomsen et al., 2006). Mortality patterns in organized dairy herds
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serve as a useful indicator for assessing the status of herd health and the efficacy of management
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programs (Prasad et al., 2004). A rise in mortality among a group of cattle can indicate sub-
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optimal health and welfare (Thomsen et al., 2004). Bangladesh is a densely populated country
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with an agricultural-based economy and its livestock play an important role. Agricultural
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livestock account for about 6.5% of total income and about 25% of the country’s population are
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directly involved in this sector. Dairy industry is a crucial component of an agro-based economy
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for a country like Bangladesh (Islam et al., 2006). Inadequate feeding, widespread disease, and
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inefficient extension services are considered among the most binding constraints on livestock
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development in Bangladesh.
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The Directorate of Livestock Services (DLS), Government of Bangladesh has established a
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Central Cattle Breeding and Dairy Farm (CCBDF) at Savar, Dhaka to meet the excessive
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demands for milk, particularly for the capital city. The success of the CCBDF partly depends on
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sound health management of the animals and efficient production techniques. However, diseases
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are one of the major health constraints for livestock development in Bangladesh. Calf mortality
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in every dairy and breeding farm results in financial and genetic loss. Cattle mortality was shown
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to be the major cause of economic losses on a dairy farm in Bangladesh (Islam et al., 2005).
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Therefore, reductions in morbidity and mortality rate are the first and foremost targets of dairy
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farm management (Prasad et al., 2004). Identification of factors that are responsible for the death
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of cattle is an important prerequisite for avoiding excessive mortality. An epidemiological
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approach usually involves collecting and evaluating pre-existing data to find associations with
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the problem.
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MATERIALS AND METHODS
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Study site: The study was conducted at the CCBDF at Savar, Dhaka, Bangladesh. The CCBDF
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was established in 1973 on 1300 acres of land with the assistance of the German Agency for
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Technical Cooperation at Savar Upazila in the Dhaka district of Bangladesh. This farm is located
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between 23O 46’ and 23 O 58’ North latitude and 90 O 12’ and 90 O 20’ East longitude and about
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30 km northwest of the capital city of Dhaka.
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Nature and source of data: For the retrospective study, the data were collected based on farm
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records of all cattle deaths over a period of 16 years (1992 to 2007) on the CCBDF. Information
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on the date of birth, sex, breed, date of death, and causes of death were collected from the farm at
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the individual animal level. The age and breed of cattle were collected from records available in
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the byre section of the farm. Initially all data were recorded on a day-to-day basis and were then
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tabulated on a master sheet on a week-by week and month-by-month basis to assess weekly,
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monthly, and yearly variations.
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Data on causes of mortality: Data on the causes of mortality were obtained from death reports
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routinely prepared by veterinarians at the Veterinary Hospital of the CCBDF. Each death report
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usually consisted of history, clinical and macroscopic post-mortem findings, and occasionally
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laboratory data. However, because most diagnoses were based on clinical grounds and post-
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mortem findings and in such cases confirmed by laboratory aids, the data were arranged into five
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major diagnostic groups as follows: (1) bacterial and mycobacterial diseases (black quarter and
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tuberculosis); (2) viral disease (foot and mouth disease); (3) protozoan disease (babesiosis); (4)
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disease syndrome (debility, enteritis, internal hemorrhage, malnutrition, pneumonia, and
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tympanitis); and (5) physiological disorder (hair ball). The data were checked manually for
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obvious inconsistencies, recording errors, or missing data.
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Statistical analysis: Microsoft Excel 2003 was used to calculate the descriptive statistics. Then
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the collected data were transferred to STATA version 11 (Stata Corporation, Texas, USA, 2009)
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for statistical analysis. The Poisson regression model was used to analyze the mortality of dairy
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cattle. All tests of statistical significance were carried out at the p <0.05 level unless otherwise
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stated.
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Results
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Mortality: A total 1759 animals died during the 16 years (1992–2007) that were evaluated.
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Among them, female cattle died more than males and the average overall mortality rate was
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5.60%. The estimated annual mortality rates and pattern of dairy cattle are illustrated in Figure 1.
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Trends in mortality indicated that the highest number of dairy cattle died in 2004 which
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accounted for 215 (11.58%) deaths. This was approximately twice the number of deaths
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compared with the previous 12 years. There was a lower level of cattle mortality rate (CMR) for
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the period of 1992 to 1999 (in those 8 years CMR varied between 1.05% and 6.07%) and a
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higher rate for the period of 2000 to 2007 during which CMR varied between 1.16% and
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11.58%.
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6
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% Mortality
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6
4
2
0
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1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Year
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Figure 1. Annual mortality rates by year for dairy cattle on the CCBDF, Savar, Bangladesh
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(1992–2007).
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Factors associated with mortality:
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Age and Sex: Mortality among dairy cattle was highest up to 365 days of age and in female
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calves, which accounted for 40.31% of deaths. The lowest mortality among dairy cattle was
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estimated in heifers (5.06%).
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Table 1. Descriptive statistics and Poisson regression analysis by age of dairy cattle mortality on
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the CCBDF, Savar, Bangladesh (1992–2007).
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Number
P-value a
Category of animal
95% confidence interval a
of deaths
Female calves ≤ 365 days
709
0.000
1.968032
2.621291
6
7
Male calves ≤ 365 days
540
0.000
1.184095
1.559081
Heifers 365 days to ≤ 730 days
89
0.258
-.1605987
.5994834
102
0.002
-.7171178 -.1634381
Bulls ≥ 731 days
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0.037
.0324649
1.062232
Cows ≥ 731 days
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0.000
.6494502
1.34968
Young bulls 365 days to ≤ 730
days
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a
Used in Poisson regression.
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Calves (71.01%) had higher mortality compared with young (10.85%) and adult cattle (18.13%).
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These differences are statistically significant (Table 1). Higher percentage of deaths was
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observed within 365 days of age and the mortality started to decrease gradually after their first
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month of life and dropped to a lower rate with the increase of age. This low rate of mortality was
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maintained during the remaining part of one year of age with slight variations between different
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age intervals (Table 2).
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Table 2. Relationship of calf mortality of different intervals age in CCBDF, Savar, Bangladesh
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(1992-2007)
No. of deaths
Mortality (%)
Age (days)
Female
Male
Total
Female
Male
Total
1-30
204
168
372
28.77
31.11
59.88
31-60
157
118
275
22.14
21.85
43.99
7
8
61-90
101
68
169
14.25
12.59
26.84
91-120
56
38
94
7.90
7.04
14.94
121-150
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30
64
4.80
5.56
10.36
151-180
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17
38
2.96
3.15
6.11
181-210
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14
29
2.12
2.59
4.71
211-240
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11
38
3.81
2.04
5.85
241-270
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16
38
3.10
2.96
6.06
271-300
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15
36
2.96
2.78
5.74
301-330
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18
39
2.96
3.33
6.29
331-365
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27
57
4.23
5.00
9.23
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Breed and Season: The highest number of cattle deaths was in the Local × Friesian herd
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category (52.70%) followed by Sindhi × Friesian (15.97), Australian × Friesian × Sahiwal (8.64),
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Local × Sindhi × Friesian (8.07), Local (4.49), Sindhi (4.32), Friesian (3.13), and 2.67% cases of
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Australian x Friesian × Sahiwal × Friesian. Table 3 depicts the seasonal mortality rates among
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different breeds. The seasonal comparison of mortality rates indicated that the overall mortality
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rate varied between 28.99% (rainy season) to 37.98% (winter season).
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Table 3. Seasonal mortality (%) in different breeds of dairy cattlea on the CCBDF, Savar,
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Bangladesh (1992–2007).
Season
Season
AFS
AFSF
F
L
LF
LSIF
SIF
SI
total
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9
Rainy
8.30
1.88
2.56
3.87
11.43
0.63
0.06
0.28
28.99
(146)b
(33)
(45)
(68)
(201)
(11)
(1)
(5)
(510)
0.06
0.40
0.17
0.34
31.67
0.17
0.11
0.11
33.03
(1)
(7)
(3)
(6)
(557)
(3)
(2)
(2)
(581)
0.28
0.40
0.40
0.28
9.61
7.28
15.80
3.92
37.98
(5)
(7)
(7)
(5)
(169)
(128)
(278)
(69)
(668)
8.64
2.67
3.13
4.49
52.70
8.07
15.97
4.32
100.00
(152)
(47)
(55)
(79)
(927)
(142)
(281)
(76)
(1759)
Summer
Winter
Overall
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a
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= Holstein Friesian; L = Local; LF = Local x Friesian; LSIF = Local × Sindhi × Friesian; SIF =
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Sindhi × Friesian; and SI = Sindhi.
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b
AFS = Australian × Friesian × Sahiwal; AFSF = Australian × Friesian × Sahiwal × Friesian; F
Values in parentheses indicate the total numbers of cattle that died during each season.
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Causes of mortality: A total of 11 types of diseases and disease syndromes responsible for the
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death of dairy cattle were identified at the CCBDF Veterinary Hospital. The overall mortality
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rates per disease or disease syndrome is shown in Table 4.
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Table 4. Specific diagnosis of diseases & syndromes responsible for dairy cattle mortality on the
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CCBDF, Savar, Bangladesh (1992-2007)
Proportional mortality rate
Diseases & syndrome
No. of deaths
(n=1759 dead)
Black quarter
31
1.76
Tuberculosis
362
20.58
FMD
26
1.48
Babesiosis
40
2.27
Debility
78
4.43
Enteritis
274
15.58
Internal Haemorrhage
38
2.16
Malnutrition
104
5.91
Pneumonia
702
39.91
Tympanitis
45
2.56
Hairball
59
3.35
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A total of 393 (22.34%) deaths were estimated to be from bacterial and mycobacterium diseases
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in which tuberculosis (20.58%) and BQ (1.76%). Of viral diseases, 26 (1.8%) of total cases were
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associated with FMD whereby it is higher in female animals (84.62%). With regards to protozoal
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diseases, total of 40 (2.27%) death were from babesiosis and mainly in female animals (97.50%)
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compared to males (2.50%).Calves had the greatest mortality accounting for 80.0% of deaths.
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Other disease syndrome accounts 55.49% of all deaths, where by pneumonia (39.91%) and
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enteritis (15.58%). Mortality caused by enteritis and pneumonia also showed makeable
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associations to the age and sex of the animal. Of all deaths, 197 (11.20%) female calves (< 365
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days) died from enteritis, and 238 (13.53%) female and 246 (13.99%) male calves were
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associated with pneumonia. A higher percentage of calves (74.36%) died from debility.
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Malnutrition accounted for 5.91% of the deaths, and 45 (2.56%) cases of tympani were
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diagnosed by history and post-mortem findings. Physiological disorder (hairball) contributed to
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3.35% of the overall mortality rate, with the highest in female calves (64.41%) followed by cows
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(25.42%), heifers (6.78%), young bulls (1.69%), and male calves (1.69%).
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Discussion
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Factors associated with mortality:
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Age and Sex: Among the deaths, more than two-thirds of mortality occurred within the first year
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of life with a greater percentage occurring in the first months. These findings are similar to
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previously reported findings (Debnath et al., 1995; Islam et al., 2005; Martin et al., 1975).
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Young calves are highly susceptible to infectious diseases as a result of lower immunity which
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can be exacerbated by in adequate colostrum intake ( Brenner et al., 1989; Oluokun et al., 1988).
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Although calf mortality on smallholder traditional dairy farms in Bangladesh has been estimated
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to be relatively lower (Debnath et al., 1990), this estimate is not applicable to the CCBDF since
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it follows an intensive animal husbandry system which differs markedly from the traditional
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extensive husbandry systems in villages. Female cattle had higher mortality rates than males,
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possibly due to the presence of a higher proportion of female animals on the farm. This is likely
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to reflect their relative value; females give birth to the calves which then join the milking herd
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and provide a regular income. Similar findings were also reported in a study of mortality pattern
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in a closed herd of dairy cattle in India ( Somavanshi, 1995 ).
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Breed and Season: The rate of mortality was higher in crossbred cattle compared with
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indigenous/local and other breeds available on the CCBDF. The higher mortality rate in
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crossbred cattle may be explained by the prevailing environmental conditions, including
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management and climate. Higher mortality in exotic and crossbred cattle could be expected in
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tropical climates because of greater susceptibility to climatic and disease stresses in such
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environments. The high rate of mortality in crossbred (Local × Holstein Friesian) cattle may
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indicate lower survivability of this breed compared with other breeds under the prevailing
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conditions of Bangladesh. This observation is in agreement with previous findings of higher
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mortality in exotic and crossbred cattle (Debnath et al., 1995). The largest number of cattle died
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in the winter season followed by the summer and rainy seasons. Higher mortality in crossbred
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cattle was observed during the summer season compared with local/indigenous and other sub-
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continent breeds. The trends of this study indicated that local/indigenous breeds had better
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adaptability for hot humid weather (summer) and higher susceptibility to cold (winter), whereas
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the opposite trend was seen in crossbreds.
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Causes of mortality: Tuberculosis was the second most important cause of death in dairy cattle
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and mortality was more common in calves and during the winter season. These findings are in
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contrast with previous studies (Mitra et al., 2005; Ramesh, 2007). In a confined herd like on the
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CCBDF, tuberculosis can be controlled and eradicated by following a “detect and discard”
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policy. Culling to reduce the population density can also decrease transmission of the disease.
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The death of cattle by BQ was lower compared with other diseases, possibly due to treatment of
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infected animals and vaccination against the disease. Among the deaths by BQ, a higher
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proportion was observed in calves within first year of life. Similarly, Sultana et al. (2008)
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reported that animals up to 12 months of age have a 6.66 times higher probability of mortality
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than animals over 12 months of age. Death by FMD showed marked age-specificity, with calves
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having the highest proportion of deaths. It should be pointed out that in a previous study; FMD
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was shown to contribute significantly to calf mortality even after regular vaccination (Debnath et
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al., 1995). This study demonstrated that FMD could be controlled and no further cases were
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reported after a certain period of time. It would, therefore, be worthwhile to improve
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management policies including destruction of infected beddings, regular use of disinfectants,
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separation of uninfected animals from infected ones, and the quality of vaccines used. Protozoan
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disease mortality of cattle from babesiosis was found to be higher in calves. This finding is
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congruent with previous findings showing that babesiosis is prevalent in calves and only calves
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(2.0%) died from babesiosis among the group of dairy cattle (Somavanshi, 1995).
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The most important disease syndrome leading to deaths was pneumonia and a higher prevalence
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of this disease was found in calves compared with adults. Similarly, other studies (Bhuller et al.,
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1985; Shimizu et al., 1987) also reported a higher proportion of calves dying from pneumonia.
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Younger age, inadequate housing for newborn calves, climatic change, and lack of care might
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contribute to the prevalence of pneumonia among calves. Enteritis is of particular importance as
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a significant number of cattle died from this syndrome. Among them, calves were more common
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than other categories of animals. Calves are more dependent on milk, milk replacer, and are
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incapable of digesting all kinds of food materials. Overfeeding, sudden change in diet, poor
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hygienic condition of feeding utensils, and calf barns might be the cause of death from enteritis.
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Pneumonia and enteritis are multifactorial diseases that are closely associated with each other
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(Debnath et al., 1995; Tikku, 1986). It has been suggested that common factors related to either
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management techniques or specific agents predispose calves to both syndromes (Waltner-Toews
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et al., 1986). Deaths caused by malnutrition were also more common in female calves.
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Alternatively, a previous study (Mulei et al., 1995) reported that mortality caused by
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malnutrition is more common in male calves. On the CCBDF it is not uncommon to find
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emaciated and neglected calves. Particularly when the feed supply is not always adequate for all
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animals or an incorrect proportion of feed ingredients is given to the animals. Debility was also
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high in female calves. Lack of vegetation, unsuitable and insufficient food, and the prevalence of
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other diseases might be the cause of debility. The majority of cattle that died from hairballs were
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calves, but a few cases of cows and heifers were also found. Hairballs in calves might originate
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from ingestion of hair during periods of excessive licking, and in adult animals is usually caused
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by itchy skin conditions. Ingestion of hair is usually associated with persistent suckling of
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penmates (Cockrill et al., 1978). Other studies (Abutarbush et al., 2006; Abutarbush et al., 2004)
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also reported on the mortality of cattle from hairballs.
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Conclusion: Among the risk factors associated with mortality, age of the animal was found to be
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the most important followed by breed and season. Greater attention should be paid to the time of
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colostrum feeding, proper timing and management of calves, and hygiene of calf barns. Because
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of the complex nature of dairy management systems, a variety of causes are responsible for
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diseases and deaths of dairy cattle.
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