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of these infections and their association with reproductive disorders is unknown in
Malawi Zebu cattle.
The objective of this study was to investigate reproductive performance and its
association with selected factors in Malawi Zebu to gain knowledge on potential
intensification. Specific objectives were (i) to determine key reproductive performance indicators (time from calving to onset of regular luteal function, calving
interval and calf mortality), (ii) to determine the relative impact of herd and cow
level factors on calving interval by variance components analyses, (iii) to study
associations between likelihood of pregnancy and availability of breeding bulls and
parity of the cows and (iv) to determine the prevalence of selected infectious agents
known to have an impact on reproductive performance.
2 Materials and Methods
A cohort study of Malawi Zebu cows was conducted in northern Malawi. The cohort
was followed by veterinary examinations, four times during a 2-year period from
September 2015 to October 2017.
Malawi is divided into 187 Extension Planning Areas (EPA), which are further
subdivided into agricultural sections comprising 5–15 villages (Kundhlande et al.
2014). This study was conducted across seven agricultural sections (Bolero, Bata,
Chozoli, Chikwawa, Chirambo, Mjuma and Jalira) of Bolero EPA, Rumphi District.
Bolero EPA was selected because smallholder livestock farming is the predominant
agrarian practice in this area (MZADD 2009).
Three farmer meetings were conducted in Bolero EPA before the start of the
study. The selection of cattle farms was based on the presence of newly calved cows
in the herd (cows that calved after August 15, 2015, and four subsequent weeks
onwards). Cows from these herds were selected based on the calving information
provided by the farmers in these three meetings.
A single-visit-multiple-subject survey technique (ILCA 1990) was used to obtain
smallholder cattle farm data including herd size, availability of breeding bulls as
well as parity, pregnancy and reproductive status of cows. Initially, 109 clinically
healthy Malawi Zebu cows from 39 smallholder farms were selected and ear tagged.
Later on, three farmers with nine cows withdrew before April 2016, leaving a cohort
of 100 cows belonging to 36 farms, which were followed throughout the study. In
this study, female calves older than 8 months were defined as heifers until first calving took place.
In addition to the permanent presence of a field assistant during the study period,
four experienced large animal veterinarians (Faculty of Veterinary Medicine,
Department of Production Animal Clinical Sciences, Norwegian University of Life
Sciences) conducted cattle rectal examinations for reproductive status and pregnancy diagnosis at four time points at approximately 6-month intervals: April 2016,
October 2016, April 2017 and October 2017. Pregnancy diagnosis was conducted
based on the following criteria:
A Cohort Study of Reproductive Performance, Associated Infections and Management…
of these infections and their association with reproductive disorders is unknown in
Malawi Zebu cattle.
The objective of this study was to investigate reproductive performance and its
association with selected factors in Malawi Zebu to gain knowledge on potential
intensification. Specific objectives were (i) to determine key reproductive performance indicators (time from calving to onset of regular luteal function, calving
interval and calf mortality), (ii) to determine the relative impact of herd and cow
level factors on calving interval by variance components analyses, (iii) to study
associations between likelihood of pregnancy and availability of breeding bulls and
parity of the cows and (iv) to determine the prevalence of selected infectious agents
known to have an impact on reproductive performance.
2 Materials and Methods
A cohort study of Malawi Zebu cows was conducted in northern Malawi. The cohort
was followed by veterinary examinations, four times during a 2-year period from
September 2015 to October 2017.
Malawi is divided into 187 Extension Planning Areas (EPA), which are further
subdivided into agricultural sections comprising 5–15 villages (Kundhlande et al.
2014). This study was conducted across seven agricultural sections (Bolero, Bata,
Chozoli, Chikwawa, Chirambo, Mjuma and Jalira) of Bolero EPA, Rumphi District.
Bolero EPA was selected because smallholder livestock farming is the predominant
agrarian practice in this area (MZADD 2009).
Three farmer meetings were conducted in Bolero EPA before the start of the
study. The selection of cattle farms was based on the presence of newly calved cows
in the herd (cows that calved after August 15, 2015, and four subsequent weeks
onwards). Cows from these herds were selected based on the calving information
provided by the farmers in these three meetings.
A single-visit-multiple-subject survey technique (ILCA 1990) was used to obtain
smallholder cattle farm data including herd size, availability of breeding bulls as
well as parity, pregnancy and reproductive status of cows. Initially, 109 clinically
healthy Malawi Zebu cows from 39 smallholder farms were selected and ear tagged.
Later on, three farmers with nine cows withdrew before April 2016, leaving a cohort
of 100 cows belonging to 36 farms, which were followed throughout the study. In
this study, female calves older than 8 months were defined as heifers until first calving took place.
In addition to the permanent presence of a field assistant during the study period,
four experienced large animal veterinarians (Faculty of Veterinary Medicine,
Department of Production Animal Clinical Sciences, Norwegian University of Life
Sciences) conducted cattle rectal examinations for reproductive status and pregnancy diagnosis at four time points at approximately 6-month intervals: April 2016,
October 2016, April 2017 and October 2017. Pregnancy diagnosis was conducted
based on the following criteria:
A Cohort Study of Reproductive Performance, Associated Infections and Management…