2. 2. The hormone was not
detectable in any of the bir
ds when active shell calcification was in progress but it was present in 6 bir
ds at the time of oviposition at a mean concentration of 1.54ng synthetic salmon CT/ml (SEM ± 0.23, range 0.95–2.48 ng/ml).
3. 3. These results are consistent with the view that CT is secreted in laying birds when the plasma level of ionic calcium exceeds 1.5 mmol/1 and that one of the physiological roles of the hormone is to limit the extent of hypercalcaemia after the completion of shell calcification.
4. 4. The effect of different levels of dietary calcium 111, 30 and 60 g/kg) on plasma CT levels in chicks were studied from 6–10 wk of age.The level of CT in the control birds (given 11 g calcium/kg diet) varied from 1.05–1.64ng synthetic salmon CT equivalents/ml and this level rose to a maximum of 2.5 ng/ml at the highest level of dietary calcium.
5. 6. Concentrations of plasma calcium increased slighly and those of plasma phosphorus decreased markedly as the level of dietary calcium increased.
6. 7. These results confirm that CT secretion in chicks is stimulated by hypercalcaemia but indicate that the hormone is unable to restore the plasma calcium to normal when diets high in calcium are fed.div>div>
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What is proper vouchering in phylogenetic studies of birds?—A reply to Peterson et al. (2007)
