Biochemical profile of fetal fluids in alpacas (Vicugna pacos) during pregnancy and immediate postpartum

Pregnancy involves characteristics unique to each species, such as the development of fetal membranes and related fluids. In this descriptive exploratory study, a unique third fetal fluid located under the epidermal membrane, in addition to the allantoic and amniotic membranes, were described in alpacas (Vicugna pacos). The aim was to characterize the biochemical composition of fetal fluids as alpaca gestation progressed. Twenty-seven pregnant alpacas were examined; 21 of them were slaughtered at various pregnancy stages to both collect allantoic and amniotic fluids, and six were monitored until parturition to obtain postpartum allantoic fluid. In the last third of pregnancy, an additional fluid was observed between the fetal skin and the epidermal membrane, herein termed as 'epidermal fluid'. Biochemical analyses were performed via spectrophotometry to measure glucose, triglycerides, cholesterol, total proteins, albumin, hemoglobin, calcium, phosphorus, uric acid, and creatinine. High variability was observed in all metabolites. Allantoic fluid showed increasing levels of uric acid, creatinine, and calcium throughout pregnancy, suggesting fetal renal function, while postpartum fluid showed reduced levels of several metabolites. The amniotic fluid displayed increased triglycerides and cholesterol, and decreased glucose levels at the end of pregnancy. Epidermal fluid exhibited the highest levels of glucose, calcium, and creatinine, and lowest uric acid compared to amniotic fluid, indicating a distinct biochemical composition. This study provides the first comprehensive insight into the biochemical characterization of fetal fluids in alpacas, updating current knowledge of fetal developmental physiology in South American camelids.