Hormonal combinations aiming to improve reproductive outcomes of Bos indicus cows submitted to estradiol/progesterone-based timed AI protocols

Author(s)

Alves, Rodrigo L. O. R. ^[1] ; Silva, Mateus A. ^[1] ; Consentini, Carlos E. C. ^[1] ; Silva, Lucas O. E. ^[1] ; Folchini, Natalia P. ^[1] ; Oliva, Abraham L. ^[2] ; Prata, Alexandre B. ^[3] ; Goncalves, Jose Renato S. ^[4] ; Wiltbank, Milo C. ^[5] ; Sartori, Roberto ^[1]

Affiliation

^[1] Univ Sao Paulo ESALQ USP, Luiz de Queiroz Coll Agr, Dept Anim Sci, BR-13418900 Piracicaba, SP - Brazil

^[2] UNAM, Cuautitlan Higher Educ Fac, Cuautitlan 54740 - Mexico

^[3] GlobalGen Vet Sci, BR-14887244 Jaboticabal, SP - Brazil

^[4] Hildegard Georgina Von Pritzelwiltz Expt Stn, BR-86010990 Londrina, Parana - Brazil

^[5] Univ Wisconsin, Dept Anim & Dairy Sci, Madison, WI 53706 - USA

• Document type: Journal article
• Source: Theriogenology; v. 169, p. 89-99, JUL 15 2021.
• Web of Science Citations: 0

Abstract

The aim was to study reproductive outcomes of Nelore (Bos indicus) cows submitted to a 7-d estradiol (E2)/progesterone (P4)-based timed artificial insemination (TAI) protocol, receiving various combinations of doses and hormones. Primiparous (n = 962) and multiparous (n = 1935) cows were submitted to synchronization (n = 2012) and resynchronization (n = 885 non-pregnant cows at pregnancy diagnosis 30 d after TAI) protocols, following a 2 x 2 x 2 factorial arrangement of eight treatments. At the initiation of the TAI protocol (Day -9), all cows received a 1.0 g intravaginal P4 insert, 2.0 mg E2 benzoate and received (PGF1) or not (PGF0) 0.5 mg cloprostenol sodium (PGF). On Day -2, the P4 insert was removed, all cows received 0.5 mg PGF, 300 IU equine chorionic gonadotropin (eCG) and 0.5 (EC0.5) or 1.0 mg estradiol cypionate (EC1.0). On Day 0, cows were treated (G1) with 8.4 mg buserelin acetate (GnRH) or not (G0), concurrently with TAI. The eight treatments were generated: 1) PGF0-EC0.5-G0 (n = 364), 2) PGF0-EC0.5-G1 (n = 363), 3) PGF1-EC0.5-G0 (n = 363), 4) PGF1-EC0.5-G1 (n = 360), 5) PGF0-EC-1.0-G0 (n = 360), 6) PGF0-EC1.0-G1 (n = 363), 7) PGF1-EC1.0-G0 (n = 361), and 8) PGF1-EC1.0-G1 (n = 363). Pregnancy per AI (P/AI) was greater at first AI compared with resynchronization (58.9 {[}n = 2012] vs. 54.9% {[}n = 885]). Presence of CL on Day -9 resulted in more cows expressing estrus (81.3 {[}n = 680] vs. 67.1% {[}n = 2033]) and greater P/AI (66.0 {[}n = 692] vs. 54.9% {[}n = 2106]). There was no difference in P/AI between cows that received or not PGF on Day -9 (58.7 {[}n = 1447] vs. 56.6% {[}n = 1450]). In contrast, PGF tended to increase P/AI of cows with CL on Day -9 (with PGF = 69.1 {[}n = 375] vs. without PGF = 62.5% {[}n = 317]). Cows that received 1.0 mg EC expressed more estrus than those treated with 0.5 mg (73.8 {[}n = 1414] vs. 67.9% {[}n = 1398]) and had greater P/AI (60.2 {[}n = 1447] vs. 55.1% {[}n = 1450]). P/AI was greater in cows treated with GnRH at TAI (59.8 {[}n = 1449] vs. 55.5% {[}n = 1448]), particularly in cows that did not show estrus (52.7 {[}n = 393] vs. 38.1% {[}n = 420]). Moreover, GnRH on Day 0 increased P/AI in cows with BCS < 3.0 (57.1 {[}n = 723] vs. 48.6% {[}n = 698]), in primiparous ( 50.1 {[}n = 465] vs. 41.9% {[}n = 497]) and in cows that received 0.5 mg EC (58.9 {[}n = 723] vs. 51.3% {[}n = 727]). In conclusion, 1.0 mg of EC on Day -2 and GnRH at TAI improved P/AI, but the combination of a higher dose of EC and GnRH treatment at AI did not enhance this effect. Furthermore, GnRH improved P/AI especially in Bos indicus cows with lower expression of estrus, such as primiparous, thinner cows, and cows treated with 0.5 mg of EC. (C) 2021 Elsevier Inc. All rights reserved. (AU)

• FAPESP's process: 18/03798-7 - Studies on ovarian and uterine physiology and improvement of Assisted Reproduction Technologies to increase reproductive efficiency in cattle
• Grantee: Roberto Sartori Filho
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 18/14723-8 - Influence of duration of follicle dominance on embryo quality and fertility of Nelore cows
• Grantee: Rodrigo Lemos Olivieri Rodrigues Alves
• Support Opportunities: Scholarships in Brazil - Master