American Bison (Bison bison) reproductive endocrinology: serum Pregnancy Associated Glycoproteins (PAG), Progesterone, Estrone and Estrone-Sulfate in non-pregnant animals and during gestation

Abstract This study describes concentrations of Pregnancy Associated Glycoproteins (PAG), progesterone (P4), estrone (E1) and estrone-sulfate (E1S) in American Bison sera. In 2 ranches, mature American Bison were sampled once a year for 2 years. Subsequent American Bison cows calving days were reported. PAG concentration was determined by Radio-Immuno Assay, whereas P4, E1 and E1S were assayed using Liquid Chromatography and Mass Spectrometry. Concentrations were compared between American Bison bulls (B, n=7), Non-Pregnant cows (NP, n=32), first (1TP, n=3), second (2TP, n=26) and third (3TP, n=15) trimester of pregnancy. Seven American Bison bulls and 92 cows were sampled, 51 calved during these 2 years. Calving occurred mostly in spring (74.5%), but also in summer (13.7%) and fall (11.8%). PAG and P4 were higher in 2TP and 3TP than B and NP (p Breeding American Bison in Belgium induces a calving seasonality loss. P4 slowly increases in 1TP and remains steady and high in 2 and 3TP. P4 non-basal and variable concentrations in B or NP disable its use as gestation marker. American Bison produce PAG in the 2 and 3TP, but Estrone-sulfate assay seems to be the best pregnancy marker during the 2 last trimesters as it could help to estimate the gestation period.