Endometrial Tissue Sampling in Angus Heifers

Animal husbandry, management, and handling procedures were under the Guide for the Care and Use of Agricultural Animals in Research and Teaching (Ag Guide 2020) [19 ]. Angus heifers (2–3 years old; n = 21) grazing Kikuyu grass (Pennisetum clandestinum) and Pangola (Digitaria eriantha) pastures were used for sampling. The estrous cycles of the heifers (n = 21) were synchronized using 25 mg of prostaglandin F2 alpha (PGF2 α; Lutalyse®, Zoetis, Parsippany, New Jersey, USA) administered intramuscularly on Day-1 (Day-1 designated as the first dose of PGF2 α) and Day-11 (Day-11 designated as the second dose of PGF2 α). Day Fifteen heifers were bred after detecting estrus. Cows were identified as pregnant (presence of conceptus) or non-pregnant (absence of conceptus). After incision of the uterus, the lumen of the uterus was exposed. Caruncles were identified as the small protuberances from the surface of endometrium, and carefully collected the protruded endometrial areas (4–5/heifer) as previously collected [20 (link)]. Caruncular endometrial tissues were collected on Day 15–17 of gestation (pregnant; n = 8) or absence of conceptus (non-pregnant; n = 7) or non-bred heifers (cyclic; n = 6) and were stored at -80 °C until further use.