The low fertility of repeat-breeder cows during summer heat stress is related to a low oocyte competence to develop into blastocysts

Abstract

It was hypothesized the lower fertility of repeat-breeder (RB) Holstein cows is associated with oocyte quality and this negative effect is enhanced during summer heat stress (HS). During the summer and the winter, heifers (H; n=36 and 34, respectively), peak-lactation (PL; n=37 and 32, respectively), and RB (n=36 and 31, respectively) Holstein cows were subjected to ovum retrieval to assess oocyte recovery, in vitro embryonic developmental rates, and blastocyst quality [terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells and total cell number]. The environmental temperature and humidity, respiration rate, and cutaneous and rectal temperatures were recorded in both seasons. The summer HS increased the respiration rate and the rectal temperature of PL and RB cows, and increased the cutaneous temperature and lowered the in vitro embryo production of Holstein cows and heifers. Although cleavage rate was similar among groups [H=51.7% ± 4.5 (n=375), PL=37.9% ± 5.1 (n=390), RB=41.9% ± 4.5 (n=666)], blastocyst rate was compromised by HS, especially in RB cows [H=30.3% ± 4.8 (n=244) vs. 23.3% ± 6.4 (n=150), PL=22.0% ± 4.7 (n=191) vs. 14.6% ± 7.6 (n=103), RB=22.5% ± 5.4 (n=413) vs. 7.9% ± 4.3 (n=177)]. Moreover, the fragmentation rate of RB blastocysts was enhanced during the summer, compared with winter [4.9% ± 0.7 (n=14) vs. 2.2% ± 0.2 (n=78)] and other groups [H=2.5% ± 0.7 (n=13), and PL=2.7% ± 0.6 (n=14)] suggesting that the association of RB fertility problems and summer HS may potentially impair oocyte quality. Our findings provide evidence of a greater sensitivity of RB oocytes to summer HS.

Developmental competence and expression profile of genes in buffalo (Bubalus bubalis) oocytes and embryos collected under different environmental stress

“…An example is highly fluctuating success rates of in vitro fertilization (IVF) and embryo transfer in the absence of explanation (Wunder et al 2005). The influence of the seasons of the year on the characteristics of the oocytes, fertilization and pregnancy rates may be importantly related to this variability, as reported previously for bovine (Rutldge et al 1999;Al-Katanani et al 2002;Sartori and Mertens 2002;Vasconcelos et al 2006;Paula-Lopes et al 2008;Roth 2008;de Torres-Júnior et al 2008;Ferreira et al 2011;Gendelman and Roth 2012a, b, c;Vieira et al 2014) and buffalo (Abdoon et al 2014;Hozyen et al 2014;Rossi et al 2014;Ali 2015;Lal et al 2015). Indeed, it is well-known that heat stress is a major concern for animal agriculture production in tropical and subtropical countries across the globe because of it's negative impact on reproduction (Ealy et al 1995).…”

Management of Repeat Breeding Syndrome in Cows

“…There are several studies pointing out towards the pathogenesis and consequences of RBS in dairy cattle, their main common point residing in the complex and plurifactorial etilogy of this syndrome (Beam and Buttler, 1999;LeBlanc et al, 2002;Spicer, 2004;Ferreira et al, 2011). The causes of RBS were shown to be often very intricate, but can nevertheless be summarized in short as follows: (1) Management factors: bad timing of insemination, missing heat detection and unprofessional insemination; (2) Semen factors: low quality of semen or infertile bulls; (3) Cow factors (undetected): endometritis, pyometra, mucometra, hydrometra, ovulatory defect, follicular cyst, adhesions, antibodies to seminal antigen, inappropriate uterine involution, infectious diseases, uterine tumours, anovulatory heats; (4) Environmental factors: heat stress, nutritional factor, etc.…”

The use of parthenotegenetic and IVF bovine blastocysts as a model for the creation of human embryonic stem cells under defined conditions

“…In vitro fertilization and embryo culture IVF and embryo culture procedures followed the standard methodology employed routinely in Vitrogen bovine IVF laboratory [5]. Briefly, groups of 15 COCs were placed in IVF medium (H199®, Vitrogen) supplemented with 6 % BSA (Sigma-Aldrich, USA).…”