Use of embryo transfer to alleviate infertility caused by heat stress

Author(s)

Baruselli, Pietro S. ^[1] ; Ferreira, Roberta M. ^[1] ; Vieira, Lais M. ^[1] ; Souza, Alexandre H. ^[1] ; Bo, Gabriel A. ^{[2, 3]} ; Rodrigues, Carlos A. ^[4]

Affiliation

^[1] Univ Sao Paulo, Dept Anim Reprod, Sao Paulo, SP - Brazil

^[2] Inst Reprod Anim Cordoba IRAC, Cordoba - Argentina

^[3] Univ Nacl Villa Maria, Cordoba - Argentina

^[4] SAMVET Embrioes, Rua Getulio Vargas 300, BR-13560000 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: Theriogenology; v. 155, p. 1-11, OCT 1 2020.
• Web of Science Citations: 0

Abstract

Heat stress (HS) has a pronounced deleterious effect on fertility in dairy herds throughout the world, especially in hot and humid summer months in tropical and subtropical areas. Summer HS reduces feed intake and increases negative energy balance, induces changes in ovarian follicular dynamics, reduces estrus detection rates and alters oviductal function leading to fertilization failure and early embryonic death. Furthermore, oocytes harvested from lactating cows during summer HS have a decreased ability to develop to the blastocyst stage after in vitro fertilization when compared with oocytes harvested during winter. The present manuscript describes the detrimental effect of HS on reproduction, with emphasis on preovulatory oocytes and carry over effects of HS on embryo development and P/AI. Embryo transfer (ET) has been an effective tool to reestablish fertility during HS because it bypasses the damage to the oocyte and early embryo caused by hyperthermia. Therefore, a management strategy to maintain increased fertility throughout the year would be to produce embryos during the cooler months, when oocyte quality is greater, and use them to produce pregnancies during the periods of HS, when oocyte quality is compromised. However, this strategy only can be implemented using cryopreserved embryos, what is still limiting. During the warmer months, the use of heifers or non-lactating cows as oocyte or embryo donors may facilitate embryo production, mainly because of the lesser deleterious effects of HS comparing to lactating cows. Also, genetic selection of donors for thermoregulation ability is one potential strategy to mitigate effects of HS and increase embryo production during the warmer months. These alternatives enable the transference of fresh embryos with more efficiency during HS periods. Additionally, the application of timed ET protocols, which avoid the need for estrus detection in recipients, has facilitated management and improved the efficiency of ET programs during HS. (C) 2020 Elsevier Inc. All rights reserved. (AU)

• FAPESP's process: 09/00938-3 - Effect of season on oocyte quality and in vitro embryo production in Holstein cows (Bos taurus) of different categories
• Grantee: Pietro Sampaio Baruselli
• Support Opportunities: Regular Research Grants
• FAPESP's process: 12/07510-1 - Molecular evaluation of oocyte maturation and use of cytoplasmic transfer to increse oocyte competence of repeat breeder dairy cows
• Grantee: Roberta Machado Ferreira Saran
• Support Opportunities: Scholarships in Brazil - Post-Doctoral