A pregnant pause in progesterone production recently helped predict the imminent arrival of two baby elephants at Chester Zoo, giving vets and keepers the early warning they needed
Serum tests run in the biochemistry department at Countess of Chester Hospital on the Advia Centaur immunoassay system, supplied by Bayer Diagnostics, indicated a sudden fall in the mother elephants' progesterone levels as the 600-660 day gestation period neared its dramatic end.
"We were approached by the zoo to see whether we could offer a fast turnaround on serum progesterone analysis using blood samples from elephants", recalls Paul Smethurst, chief biomedical scientist in the hospital laboratory.
"We explained that we had an immunoassay analyser, the Advia Centaur, which could be used to process the samples automatically so that results would be available within a couple of hours.
"The zoo then provided us with some samples to see what we could make of them. "Elephants have low progesterone levels during pregnancy as compared to humans, so the first thing we had to do was see whether or not we could measure them", he continues. "Having established that the Advia Centaur was equal to the task, we were able to start running samples on a serial basis leading up to the births, alongside our routine human workload. "Evidence obtained from Whipsnade Zoo indicated that there would be a dramatic fall in the serum progesterone level when labour was imminent.
"We acquired some normal range data and ran the samples just like any human specimens.
"The Advia Centaur progesterone assay certainly appeared to be valid for this application because we were getting a plateau level which dropped as soon as the mother elephants came up to term. "This enabled us to provide valid clinical information to the zoo's veterinary staff".
Tests were initially run on a weekly basis, and then more frequently as the expected time for labour approached.
Results were telephoned through to the zoo as soon as the progesterone levels were seen to fall, prompting the vets and elephant keepers to begin a 24-hour ante-natal vigil in the elephant house.
Sadly, the first pregnancy resulted in a still birth, but the other produced a healthy female calf - a second generation addition to the zoo's established breeding colony.
"Contrary to what you might expect, the size of the samples we received was not huge", Smethurst says.
"The red blood cells of elephants are quite small in comparison to humans, and because they are herbivores their serum is very pale due to lack of bilirubin production.
"We are hoping to continue our involvement as the zoo's next elephant pregnancy approaches full term in September 2004."
