Administering an additional prostaglandin F2α injection to Bos indicus beef cows during a treatment regimen for fixed-time artificial insemination

• Published in: Animal reproduction science Vol. 219; p. 106535
• Main Authors: Noronha, Isabella M., Cooke, Reinaldo F., Martins, Cícero F.G., Oliveira Filho, Ramiro V., Pohler, Ky G., Vasconcelos, José L.M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2020
• Subjects: Beef cows; Fixed-time artificial insemination; Pregnancy; Prostaglandin F2α; Pregnancy; Beef cows; Fixed-time artificial insemination; Prostaglandin F2α
• ISSN: 0378-4320; 1873-2232
• DOI: 10.1016/j.anireprosci.2020.106535

•Prostaglandin (PG) F2α is known to stimulate LH release in beef cows.•Cows in poor nutritional status are often in anestrus due to inadequate LH release.•This study evaluated one vs. two PGF2α injections during estrous synchronization.•Two PGF2α injections increased pregnancy rates per fixed-time artificial.•This outcome was mostly noted in cows with body condition score less than 5.0. Two experiments were conducted to evaluate if an additional prostaglandin F2α (PG) injection during an estradiol-based estrous synchronization treatment regimen affects pregnancy rates resulting from fixed-time artificial insemination (FTAI) in Nelore cows. In Experiment 1, 1039 cows were administered estradiol benzoate and an intravaginal progesterone releasing device (CIDR) on d -11, an injection of PG on d -4, with CIDR removal and administration of estradiol cypionate and eCG occurring on d -2, and FTAI on d 0. Cows were administered an additional injection of PG (PG2) or saline (PG1) on d -2. Percentage pregnancy per FTAI on d 30 was greater (P = 0.01) in cows of the PG2 than PG1 group (54.5 % and 46.6 %, respectively). In Experiment 2, there was use of the same treatment regimen for estrous synchronization of 934 cows as that for Experiment 1 followed by FTAI, with there being diagnosis of whether cows had or did not have a corpus luteum on d -4. Response to estrous synchronization, largest follicle diameter at FTAI, and pregnancy per FTAI were greater (P ≤ 0.05) in cows of the PG2 than PG1 group with a body condition score (BCS) < 5.0 at FTAI (81.2 % and 72.6 %, 11.9 and 11.2 mm, 55.5 and 45.6 %; respectively). These treatment responses did not differ (P ≥ 0.18) in cows with BCS ≥ 5.0. Collectively, results indicate that treatment with PG2 increased pregnancy per FTAI in B. indicus cows deficient in body energy reserves, by enhancing follicle development and estrous synchronization response.