Luteolysis in Bos indicus cows on Days 5 and 7 of estrous cycle with varying doses of PGF(2 alpha)

Author(s)

Ferraz Junior, Marcos Vinicius C. ; Pires, Alexandre V. ; Biehl, Marcos Vinicius ; Santos, Marcelo Henrique ; Polizel, Daniel M. ; Nepomuceno, Delci D. ; Sartori, Roberto ; Barreto Filho, Joao Bosco ; Goncalves, Jose Renato S. ; Day, Michael L.

• Document type: Journal article
• Source: Theriogenology; v. 86, n. 5, p. 1268-1274, SEP 15 2016.
• Web of Science Citations: 2

Abstract

The aim of this study was to evaluate luteolysis using three doses of PGF(2 alpha) on Day 5 or Day 7 of the estrous cycle in nonlactating Nellore (Bos indicus) cows. Cows (n = 323) were assigned within date of estrus (Day 0 of estrous cycle) to receive 12.5, 25.0, or 50.0 mg of PGF(2 alpha) on either Day 5 or Day 7 of the estrous cycle in a 3 x 2 factorial arrangement. Blood samples for progesterone (P-4) concentrations were collected at 0, 24, 48, and 72 hours after PGF(2 alpha) to assess luteolysis (L). Luteolysis was defined on the basis of P-4 concentrations at 72 hours using either less than 0.5 ng/mL (L0.5) or less than 1.0 ng/mL (L1.0) as the cut off. Luteolysis was considered ``partial{''} when P-4 concentration declined within 24 hours after PGF(2 alpha) but failed to decline further or, in some cases, increased. Incidence of luteolysis was less (P < 0.01) on Day 5 than Day 7 of the estrous cycle (17.3 vs. 47.6% and 30.4 vs. 77.2%; for L0.5 and L1.0, respectively). Dose of PGF(2 alpha) increased (P < 0.01) L1.0 (12.5 mg = 38.9%; 25.0 mg = 523%; and 50.0 mg = 70.4%). Incidence of partial luteolysis for cows on Day 5 (57.1%) was greater (P < 0.01) than that on Day 7 (19.1%) of the estrous cycle and was more prevalent (P < 0.01) with lower doses of PGF(2 alpha) (12.5 mg = 49.1%; 25.0 mg = 37.4%; and 50.0 mg = 27.8%). In conclusion, both days of the estrous cycle and doses of PGF(2 alpha) influenced the incidence of complete and partial luteolysis in Nellore cows and should be an important consideration when devising estrus synchronization programs in this species. (C) 2016 Elsevier Inc. All rights reserved. (AU)

• FAPESP's process: 12/01345-9 - Pharmacological manipulation of the estrous cycle in Nellore cows: I - Effect of doses of PGF2a for luteolysis on days 5 and 7 of the estrous cycle. II - Effect of replacement of GnRH by EB, in the 5 Co-Synch program, at estrus detection and distribution
• Grantee: Alexandre Vaz Pires
• Support Opportunities: Regular Research Grants