230
• Membrane slip + asymmetry (>35 days pregnant).
• Balloting of the foetus (>70 days).
• Fremitus in one of the uterine arteries (>105 days).
• Fremitus in both uterine arteries (>180 days).
• Large parts of the foetus apparent close to the pelvic inlet (>240 days).
An early abortion was suspected if cows were not late pregnant or had not calved
within 8 months after diagnosis of an early pregnancy (>35 days). The terms late
abortion and stillbirth were used for the foetus of the last trimester or full born
calves dead at birth. If a cow with an assumed early abortion later became pregnant,
the successful calving of a live calf was included in the assessment of the calving
interval. The herd record keeping was regularly maintained by the farmers and monitored by the field assistant. Calving dates were obtained from these herd records,
which enabled the calculation of calving intervals. Days from calving to pregnancy
were approximated by subtracting 280 days from the next calving date. Observations
of calf mortality in live born calves were restricted to the period from the date the
calf was born until the end of December 2015.
The animals were treated for ticks in April 2016 and 2017 (Taktic®, Utrecht, The
Netherlands) and for helminths in October 2016 and October 2017 (Kepromec®,
Deventer, The Netherlands). Treatments were conducted in accordance with the
manufacturer’s recommendations.
2.1 Milk Sampling
Altogether, 96 cows (four cows omitted due to sampling irregularity) were subjected to milk progesterone analyses. A semi-quantitative assessment of progesterone in milk was performed using a cow-side P4 Rapid test (Ridgeway Science, St
Briavels, UK). Progesterone analyses were used to determine the time from calving
to onset of luteal activity (OLA) defined as three consecutive positive reactions to
elevated milk progesterone values within 21 days. Milk was collected every third to
seventh day from October to the end of December 2015.
2.2 Blood Sampling
Blood was sampled on three occasions: October 2015, April 2016 and October 2016
from 108, 99, and 81 cows, respectively. Blood was collected from either the coccygeal vein or the jugular vein into sterile vacutainers and immediately cooled in the
field cooler until centrifugation at 1200 × g at room temperature. Sera were pipetted
into sterile tubes and kept frozen at approximately −20 °C. The material was
shipped on ice to the National Veterinary Institute in Oslo, Norway, and submitted
to the Biosafety level 3 laboratories and kept frozen at −20 °C until analyses. EDTA
M. A. Bhatti et al.
• Membrane slip + asymmetry (>35 days pregnant).
• Balloting of the foetus (>70 days).
• Fremitus in one of the uterine arteries (>105 days).
• Fremitus in both uterine arteries (>180 days).
• Large parts of the foetus apparent close to the pelvic inlet (>240 days).
An early abortion was suspected if cows were not late pregnant or had not calved
within 8 months after diagnosis of an early pregnancy (>35 days). The terms late
abortion and stillbirth were used for the foetus of the last trimester or full born
calves dead at birth. If a cow with an assumed early abortion later became pregnant,
the successful calving of a live calf was included in the assessment of the calving
interval. The herd record keeping was regularly maintained by the farmers and monitored by the field assistant. Calving dates were obtained from these herd records,
which enabled the calculation of calving intervals. Days from calving to pregnancy
were approximated by subtracting 280 days from the next calving date. Observations
of calf mortality in live born calves were restricted to the period from the date the
calf was born until the end of December 2015.
The animals were treated for ticks in April 2016 and 2017 (Taktic®, Utrecht, The
Netherlands) and for helminths in October 2016 and October 2017 (Kepromec®,
Deventer, The Netherlands). Treatments were conducted in accordance with the
manufacturer’s recommendations.
2.1 Milk Sampling
Altogether, 96 cows (four cows omitted due to sampling irregularity) were subjected to milk progesterone analyses. A semi-quantitative assessment of progesterone in milk was performed using a cow-side P4 Rapid test (Ridgeway Science, St
Briavels, UK). Progesterone analyses were used to determine the time from calving
to onset of luteal activity (OLA) defined as three consecutive positive reactions to
elevated milk progesterone values within 21 days. Milk was collected every third to
seventh day from October to the end of December 2015.
2.2 Blood Sampling
Blood was sampled on three occasions: October 2015, April 2016 and October 2016
from 108, 99, and 81 cows, respectively. Blood was collected from either the coccygeal vein or the jugular vein into sterile vacutainers and immediately cooled in the
field cooler until centrifugation at 1200 × g at room temperature. Sera were pipetted
into sterile tubes and kept frozen at approximately −20 °C. The material was
shipped on ice to the National Veterinary Institute in Oslo, Norway, and submitted
to the Biosafety level 3 laboratories and kept frozen at −20 °C until analyses. EDTA
M. A. Bhatti et al.