A technique for continuously monitoring hormone levels in lactating sows and results obtained using it to study LH...

A technique for collecting continuously blood was successfully applied for the first time in lactating sows. A double-lumen catheter consisted of an internal tubing for delivering an anticoagulant (heparin-saline) and an outer tubing for blood collection. An automatic system, composed of a blood withdrawal pump, an anticoagulant infusion pump and a fraction collector, was connected to the catheter and operated for 12 h on Days 10 and 20 of lactation. Blood samples were collected continuously at a rate of 1 ml per min from four sows. Each fraction consisted of 4 ml blood except during nursing periods when 1 ml blood per fraction was collected. In this study, aliquots of plasma were combined to form pooled 8-min samples for the measurement of the concentrations of LH. Average and base levels of LH, number of LH pulse(s)/12 h and pulse durations were calculated for all pooled samples, all even-numbered samples and all odd-numbered samples. Average and base levels of LH and the number of LH pulses were slightly higher on Day 20 than on Day 10 of lactation. The LH-pulse duration varied between animals, with the value for one of the sows diverging greatly from those of the others. When only every second sample was considered, the LH-pulse rate appeared to be slightly lower.