Plasma concentrations of 15-ketodihydro-PGF2 alpha, progesterone, oestrone sulphate, oestradiol-17 beta and cortisol during late gestation, parturition and the early post partum period in llamas and alpacas.

Plasma concentrations of 15-ketodihydroprostaglandin (PG) F2 alpha, progesterone, oestrone sulphate, oestradiol-17 beta and cortisol during late gestation, parturition and the early post-partum period were measured in six llamas and five alpacas. During the last 100 days of pregnancy, 15-ketodihydro-PGF2 alpha concentrations increased steadily until the day of parturition when a massive release was detected (P < 0.01) concomitant with a decrease in progesterone concentrations (P < 0.01). The highest PGF2 alpha metabolite concentrations (159 +/- 35 nmol l-1 and 92 +/- 29 nmol l-1 in llamas and alpacas respectively) were detected in the sample collected during the morning on the day of parturition. Basal concentrations were registered by day 3 after delivery. Plasma concentrations of oestrone sulphate started to increase 80 days before parturition and reached peak concentrations immediately before parturition (15 +/- 3 nmol l-1 in llamas and 18 +/- 5 nmol l-1 in alpacas). Oestrone sulphate concentrations dropped sharply (P < 0.01) on the day of parturition in llamas and one day later in alpacas, whereupon they remained relatively unchanged until at least 20 days postpartum. Oestradiol-17 beta concentrations were higher than 180 pmol l-1 during the last 45 days of pregnancy, began to decrease on the day of parturition and reached very low concentrations within the following two days. High oestradiol-17 beta concentrations were registered 7 days postpartum in all alpacas (P < 0.05) and within 10 days of parturition in five of six llamas (P < 0.01). No significant cortisol peaks were observed around parturition, but mean concentrations were increased in both species.