241
2 Materials and Methods
In order to assess the association between the outcome variables and the intervention, a field experimental study was conducted in Bolero EPA, Rumphi district,
Malawi. The outcomes were calving interval (days), length of the lactation period
(days) and body weight attainment in calves (cm changes in body girth); and the
intervention was supplemental feeding of the dam. Herds from seven agricultural
sections were represented: Bolero, Bata, Chozoli, Chikwawa, Chirambo, Mjumba
and Jalir.
A total of 98 cows were included in the study. They were enrolled at calving and
followed for 15 months. The study was conducted for two consecutive years. The
first trial (n = 56) commenced at calving between August 15th and September 12th
in 2015 and ended on December 22nd in 2016, and the second trial (n = 42) started
at calving between August 1st and September 19th in 2016 and ended on December
22nd in 2017. Half of the cows (n = 49) were assigned to a control group with no
additional feeding, and the other half (28 in 2015 and 21 in 2016) were assigned to
an experimental group receiving supplementary feeding. The extra feeding consisted of Gliricidia sepium leaves and maize bran and was given only during the
driest months of the year: October, November and December. For both experimental
groups, 2 kg maize bran was given per cow per day. In the first year of the study,
each of the experimental cows was fed 114 kg leguminous leaves during the dry
period (experimental group 1). The quantity of leaves was increased to 240 kg per
cow for experimental cows in the second year of the study (experimental group 2).
This gave us a total of four experimental groups: experimental group 1 (low-level
additional feeding), experimental group 2 (high-level additional feeding), and two
control groups for years 1 and 2, respectively (Table 1). Each pair of control and
experimental cows was matched according to calving date (±15 days), parity of the
dam (first, second and third parity and older) and within one out of the seven agricultural sections.
The feed was analysed for dry matter, ash (oven drying) and crude protein by
Kjeldahl using the AOAC (2000) procedures at the Animal Science Department,
Lilongwe University of Agriculture and Natural Resources, Malawi. Gross energy
was calculated using 6100 Oxygen Bomb Calorimeter (Yan and Kim 2011). The
acid detergent fibre was analysed by using an Ankom fibre analyser and Ankom
(xt10) extractor as described by (Cao et al. 2009).
Reproductive outcome was measured as time from recruitment at calving in
2015 or 2016 and until next calving occurred within 15 months (calving interval).
The follow-up period in each of the years ended on December 22nd the year after
(2016 and 2017). Data from both years were collated (n = 98), and calving (n = 58)
Table 1 The study design for supplementary feeding in years 2015 and 2016
Year Supplementary feed group (n) Control group (n) Supplementary feed offered (kg/cow)
2015 28
28
114
2016 21
21
240
Effect of Dry Season Supplement Feeding of Malawi Zebu Cows on Reproductive…
2 Materials and Methods
In order to assess the association between the outcome variables and the intervention, a field experimental study was conducted in Bolero EPA, Rumphi district,
Malawi. The outcomes were calving interval (days), length of the lactation period
(days) and body weight attainment in calves (cm changes in body girth); and the
intervention was supplemental feeding of the dam. Herds from seven agricultural
sections were represented: Bolero, Bata, Chozoli, Chikwawa, Chirambo, Mjumba
and Jalir.
A total of 98 cows were included in the study. They were enrolled at calving and
followed for 15 months. The study was conducted for two consecutive years. The
first trial (n = 56) commenced at calving between August 15th and September 12th
in 2015 and ended on December 22nd in 2016, and the second trial (n = 42) started
at calving between August 1st and September 19th in 2016 and ended on December
22nd in 2017. Half of the cows (n = 49) were assigned to a control group with no
additional feeding, and the other half (28 in 2015 and 21 in 2016) were assigned to
an experimental group receiving supplementary feeding. The extra feeding consisted of Gliricidia sepium leaves and maize bran and was given only during the
driest months of the year: October, November and December. For both experimental
groups, 2 kg maize bran was given per cow per day. In the first year of the study,
each of the experimental cows was fed 114 kg leguminous leaves during the dry
period (experimental group 1). The quantity of leaves was increased to 240 kg per
cow for experimental cows in the second year of the study (experimental group 2).
This gave us a total of four experimental groups: experimental group 1 (low-level
additional feeding), experimental group 2 (high-level additional feeding), and two
control groups for years 1 and 2, respectively (Table 1). Each pair of control and
experimental cows was matched according to calving date (±15 days), parity of the
dam (first, second and third parity and older) and within one out of the seven agricultural sections.
The feed was analysed for dry matter, ash (oven drying) and crude protein by
Kjeldahl using the AOAC (2000) procedures at the Animal Science Department,
Lilongwe University of Agriculture and Natural Resources, Malawi. Gross energy
was calculated using 6100 Oxygen Bomb Calorimeter (Yan and Kim 2011). The
acid detergent fibre was analysed by using an Ankom fibre analyser and Ankom
(xt10) extractor as described by (Cao et al. 2009).
Reproductive outcome was measured as time from recruitment at calving in
2015 or 2016 and until next calving occurred within 15 months (calving interval).
The follow-up period in each of the years ended on December 22nd the year after
(2016 and 2017). Data from both years were collated (n = 98), and calving (n = 58)
Table 1 The study design for supplementary feeding in years 2015 and 2016
Year Supplementary feed group (n) Control group (n) Supplementary feed offered (kg/cow)
2015 28
28
114
2016 21
21
240
Effect of Dry Season Supplement Feeding of Malawi Zebu Cows on Reproductive…