02982naa a2200277 a 450000100080000000500110000800800410001902200140006002400460007410000250012024502130014526000090035850004060036752015900077365300140236365300180237765300340239565300140242965300490244365300150249265300260250770000170253370000190255070000180256977301170258710637042022-11-07       2022    bl uuuu     u00u1 u    #d  a0093-691X7 a10.1016/j.theriogenology.2022.10.0162DOI1 aARAGUNDE VIEYTES, R.  aEquine chorionic gonadotropin administered on day 5 of a 7-days fixed-time artificial insemination program improves ovulation synchrony and corpus luteum function in anestrous beef cowsh[electronic resource]  c2022  aArticle history: Received 17 June 2022; Received in revised form 5 October 2022; Accepted 12 October 2022; Available online 17 October 2022. Correspondence authors:  Gastal, G.D.A.; Ruta 11, Km 50, Colonia del Sacramento, Colonia, Uruguay; email:ggastal@inia.org.uy  --   Aragunde Vieytes, R.; Facultad de Veterinaria, UDELAR, Ruta 1, km 42.5, Montevideo, Uruguay; email:rafaelaragunde@fvet.edu.uy  --  aABSTRACT.- In order to assess the effect of equine chorionic gonadotropin (eCG) administered on Day 5 or 7 of a fixed-time artificial insemination protocol (FTAI) in anestrous suckled beef cows, two experiments were performed to determine the following endpoints: Experiment 1 (n = 22), preovulatory follicle (POF) diameter, ovulation time, corpus luteum (CL) area, estradiol (E2) and progesterone (P4) concentrations; and Experiment 2 (n = 676), a field trial to evaluate conception rate using the same experimental design. In both experiments, a synchronization protocol using estradiol benzoate (EB) (Day 0), intravaginal progestin device (IVD) (Days 0 through 7), prostaglandin (PGF) (Day 7), eCG (Day 5 or 7), and GnRH (Day 9). Treatment consisted of administering 400 IU of eCG on Day 5 (T5) or Day 7 (T7 or control) concomitant with treatment with PGF2α. In experiment 1, all cows of T5 ovulated by 16 h after GnRH administration. The POF tended (P = 0.06; P = 0.07) to be larger at 1 and 2 d before ovulation in T5. The day before ovulation, E2 tended to be lower (P = 0.06) in T5 compared with T7. The CL area and the P4 concentrations were greater (P = 0.04) on day 9 in T5 compared with T7. In experiment 2, the conception rate was greater (P = 0.04) in T5 (72.2%) compared with T7 (61.0%) group. Therefore, administration of eCG on Day 5 of the designed protocol hastened ovulation of a greater follicle, which produced a larger CL and greater concentrations of progesterone by Day 9 after ovulation, resulting in 11.2% increase in cows pregnant. © 2022 Elsevier Inc.  aAnestrous  aCorpus luteum  aEquine chorionic gonadotropin  aOvulation  aPLATAFORMA DE INVESTIGACIÓN EN SALUD ANIMAL  aPostpartum  aPreovulatory follicle1 aVIÑOLES, C.1 aGASTAL, G.D.A.1 aCAVESTANY, D.  tTheriogenology, January 2023, Volume 195, Pages 62-68. doi: https://doi.org/10.1016/j.theriogenology.2022.10.016