At 9 a.m. on day 5 post-oestrus, a single blood sample (10 ml) was collected by jugular
venipuncture. Plasma was harvested by centrifugation for 10 min at 1500×g and stored
at −20 ◦C for subsequent hormone analysis. Immediately after blood sampling, cows were
euthanised by captive bolt and exsanguination. The reproductive tract was recovered within
10 min and transported to the laboratory within 30 min of slaughter