Use of color-Doppler ultrasonography for selection of recipients in timed-embryo transfer programs in beef cattle

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Published on: August 13, 2020

Guilherme Pugliesi 1Gabriela Dalmaso de Melo 2Júlio Barboza Silva 3Alexandre Sardinha Carvalhêdo 4Everton Lopes 2Emivaldo de Siqueira Filho 4Luciano Andrade Silva 5Mario Binelli 6

  • 1Department of Animal Reproduction, School of Veterinary Medicine and Animal Science, University of São Paulo, Pirassununga, São Paulo, Brazil. Electronic address: gpugliesi@usp.br.
  • 2Department of Animal Reproduction, School of Veterinary Medicine and Animal Science, University of São Paulo, Pirassununga, São Paulo, Brazil.
  • 3Department of Veterinary Medicine, School of Animal Science and Food Engineering, University of São Paulo, Pirassununga, São Paulo, Brazil; Embryo SYS, Ouro Fino, MG, Brazil.
  • 4Embriotec Reprodução Animal, Anápolis, GO, Brazil.
  • 5Department of Veterinary Medicine, School of Animal Science and Food Engineering, University of São Paulo, Pirassununga, São Paulo, Brazil.
  • 6Department of Animal Sciences, University of Florida, Gainesville, FL, USA.

Abstract

We aimed to study the association between CL characteristics assessed by color-Doppler ultrasonography (Doppler-US) at the time of embryo transfer (ET) and pregnancy rate (P/ET) in beef recipients. Estrous cycles of crossbred beef recipients were synchronized for timed-ET. On the day of ET (Day 7), CL area, proportion of luteal blood perfusion (BP), and the relationship between the largest dominant follicle (DF) and CL (ipsilateral or contralateral) were determined. Animals (n = 444) received an in vitro produced embryo from Nelore donors, placed in the uterine horn ipsilateral to the CL. Recipients were split retrospectively in three subgroups according to CL area [small (<3 cm2), medium (3-4 cm2), or large (>4 cm2)] and three subgroups according to luteal signals of BP [low (≤40%), medium (45-50%) or high (≥55%)]. Pregnancy was detected on Days 30-45 by transrectal ultrasonography and P/ET was analyzed considering the effects of cow’s category (suckling or non-suckling), CL area, luteal BP and side of DF. P/ET increased along with BP category [low, 45.9%B, (62/135); medium, 54.1%AB (93/172); and high, 58.4%A (80/137)]. When luteal BP was evaluated as a continuous variable, a significant (P < 0.05) linear and positive effect was observed on P/ET. A greater (P < 0.05) CL area and serum progesterone concentrations were observed in the medium and high BP than in the low BP category. Although an effect of luteal size category was not significant on P/ET [small, 49% (76/155); medium, 59.7% (83/139); and large, 50.7% (75/148); P > 0.1], when CL area was evaluated as a continuous variable, a quadratic effect (P < 0.05) indicated a positive relationship between P/ET and CL area until luteal tissue reached 4.07 cm2, followed by a negative relationship. The location of the first-wave DF in relation to the CL did not affect P/ET (P > 0.1). In conclusion, Doppler-US is an innovative tool that has the potential to be used for selection of suitable embryo recipients based on luteal BP. Selection of recipients that have a greater chance of maintaining pregnancy will increase the success of timed-ET programs.

Keywords: Blood perfusion; Cattle; Corpus luteum; Follicle; Pregnancy success.

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