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

Author(s):Show less -

Ferreira, R. M. ^[1] ; Ayres, H. ^[1] ; Chiaratti, M. R. ^[2] ; Ferraz, M. L. ^[3] ; Araujo, A. B. ^[3] ; Rodrigues, C. A. ^[4] ; Watanabe, Y. F. ^[5] ; Vireque, A. A. ^[5] ; Joaquim, D. C. ^[5] ; Smith, L. C. ^[6] ; Meirelles, F. V. ^[2] ; Baruselli, P. S. ^[1]

Affiliation

^[1] Univ Sao Paulo, Fac Med Vet & Zootecnia, Dept Anim Reprod, BR-05508000 Sao Paulo - Brazil

^[2] Univ Sao Paulo, Fac Zootecnia & Engn Alimentos, Dept Ciencias Basicas, BR-13635900 Pirassununga, SP - Brazil

^[3] Vida Reprod Consultoria, BR-14140000 Cravinhos, SP - Brazil

^[4] Clin Vet SAMVET Sao Carlos Ltda, BR-13570390 Sao Carlos, SP - Brazil

^[5] VITROGEN Pesquisa & Desenvolvimento Biotecnol Rep, BR-14140000 Cravinhos, SP - Brazil

^[6] Univ Montreal, Fac Med Vet, Ctr Rech Reprod Anim, St Hyacinthe, PQ J2S 7C6 - Canada

• Document type: Journal article
• Source: JOURNAL OF DAIRY SCIENCE; v. 94, n. 5, p. 2383-2392, MAY 2011.
• Web of Science Citations: 69

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. (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