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Use of a vascular access port for the measurement of pulsatile luteinizing hormone in old broiler breeders.

Techniques used to measure circulating hormone concentrations in avian species over extended periods routinely involve cannulation or multiple venipunctures under physical restraint, resulting in sepsis and stress. We adapted a method for serial blood sampling in chickens using a vascular access port (VAP) surgically implanted under the skin of the neck and connected to a catheter inserted in the right jugular vein. The system was used to measure circulating luteinizing hormone (LH) profiles in six, 21-mo-old broiler breeders at the end of their laying period. The VAP were implanted under general anesthesia, and, after a period of recovery, serial blood samples (every 10 min for 6 h) were collected using an extension line connected to a push-pull system. Birds were unrestrained and had free access to food and water. Red blood cells were recovered by centrifugation, reconstituted in saline solution, and returned to the donor bird through the VAP once every 90 min. Luteinizing hormone levels were subsequently measured in plasma by radioimmunoassay. With the exception of 1 hen that developed valvular endocarditis, no sign of disease or infection was observed throughout the study, and the VAP remained functional in all birds for at least 3 mo. Thus, our results suggest that VAP are a safe, reliable, and less stressful technique for serial blood sampling and long-term studies. Radioimmunoassay results revealed that in old birds, circulating LH levels followed a pulsatile pattern, with pulse amplitudes ranging from 1.35 to 2.02 ng/mL and pulse frequencies ranging from 5 to 6 peaks per 6 h. Although not significant, amplitude of LH pulses in out-of-lay hens appeared to be lower than in laying hens.