Endocrine changes during pregnancy, parturition and the early post-partum period in the llama ( <i>Lama glama</i> )

Abstract

Summary. Mean (± s.d.) pregnancy length for the 14 llamas in this study was 350 ± 4·5 days. Plasma progesterone concentrations increased by 5 days after mating and remained elevated (&amp;gt;2·0 ng/ml) throughout most of pregnancy. At about 2 weeks before parturition, plasma progesterone concentrations began to decline, dropped markedly during the final 24 h before parturition, and returned to basal concentrations (&amp;lt;0·5 ng/ml) by the day of parturition. The combined oestrone + oestradiol-17β and oestradiol-17β concentrations varied between 6 and 274 pg/ml and 4 and 114 pg/ml, respectively, during the first 9 months of pregnancy. Concentrations increased between 9 months after mating and the end of pregnancy with peak mean concentrations of 827 ± 58 (s.e.m.) pg oestrone + oestradiol-17β/ml (range: 64–1658) and 196 ± 10 pg oestradiol-17β/ml (31–294) during the last week of pregnancy. Concentrations then declined to 87 ± 14 pg oestrone + oestradiol-17β/ml (7–488) and 25 ± 5 pg oestradiol-17β/ml (2·5–142) during the first week post partum. Plasma cortisol concentrations varied between 2·6 and 51·9 ng/ml (14·0 ± 0·5) from mating until 2 weeks before parturition when the concentrations began to decline. Only a slight increase in plasma cortisol concentrations was observed in association with parturition. Plasma triiodothyronine concentrations varied between 0·5 and 4·5 ng/ml (1·9 ± 0·1) throughout pregnancy and the periparturient period. Plasma thyroxine concentrations varied between 21·3 and 91·5 ng/ml (56·5 ± 0·8) from mating until about 39 weeks of pregnancy when they began to decline, from 43·0 ± 5·3 ng/ml at 15 days pre partum to 23·5 ± 5·5 ng/ml immediately before parturition, but then increased to 52·8 ± 3·9 ng/ml by 1 day post partum. Keywords: llama; pregnancy; post partum; progesterone; oestrogen; parturition