Elemental composition of placental cotyledons in cows with retained placenta

Disruptions in elemental homeostasis in the "mother-placenta-fetus" system, often linked to animal feeding errors and exposure to ecotoxicants, negatively affect fetal development and the birthing process. In this study, we performed a comparative analysis of the elemental composition of placental cotyledons in cows with normal delivery and those with retained placenta. We examined 120 Simmental cows, recording the time between calf birth and placenta detachment. We diagnosed retained placenta cases when this time exceeded 12 h. We collected cotyledon samples from the fetal portion of the placenta in 20 cows with normal deliveries and 18 cows with retained placenta for analysis. We quantitatively determined 27 chemical elements in the samples via inductively coupled plasma mass spectrometry (ICP-MS) using a Nexion 300D spectrometer (Perkin Elmer, USA). We performed statistical analysis using IBM SPSS Statistics 20.0 (IBM Corp., USA), assessing the significance of differences between the samples using the Mann-Whitney U test for independent variables at a significance level of P < 0.05. We determined the correlations between the time of placental detachment and the content of chemical elements in the cotyledons using Spearman's rank correlation coefficient. The elemental composition of placental cotyledons in cows with retained placenta exhibited a distinct profile compared to that of cows with normal deliveries. The retained placenta group showed significantly elevated levels of magnesium (27.0%, P = 0.016), copper (69.4%, P = 0.010), molybdenum (32.7%, P = 0.031), nickel (196.1%, P = 0.023), vanadium (20.8%, P = 0.049), arsenic (102.2%, P = 0.0001), lithium (61.3%, P = 0.007), aluminum (94.5%, P = 0.011), lead (370.2%, P = 0.006), beryllium (125.8%, P = 0.005), and tin (246.4%, P = 0.001). We demonstrated that the time of placental detachment in cows was directly correlated with the levels of the abovementioned elements in the samples, except for nickel. The concentrations of boron, calcium, cadmium, cobalt, chromium, iron, mercury, iodine, potassium, manganese, sodium, phosphorus, selenium, silicon, strontium, and zinc in the placental cotyledons did not significantly differ between healthy animals and those with retained placenta. In this article, we also discuss the role of the identified disruptions in elemental homeostasis in the physiology and pathology of the placenta.