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

Departamento de Reprodução Animal da Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo, São Paulo, SP, Brazil 05508-000.
Journal of Dairy Science (Impact Factor: 2.57). 05/2011; 94(5):2383-92. DOI: 10.3168/jds.2010-3904
Source: PubMed


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.

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    • "P < 0.0001) in Holstein donors. In addition, Ferreira et al. (2011) reported decreased COC numbers in Holstein cows when OPU was performed during the summer months. Yet, when blastocyst rates were evaluated, an interaction between group and season indicated that the effect of season was dependent on animal category. "

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    • "Reproductive technologies , such as in vitro embryo production (IVP), have been applied worldwide to rapidly enhance the genetics of dairy and beef cattle through the female lineage. However, the efficiency of this technique has been impaired by the large variability among donors in their response to IVP procedures [1] [2] [3] [4]. Therefore, the success of in vitro embryo technologies has been associated primarily with physiological characteristics, such as ovarian antral follicle population (AFP) and oocyte competence (eg, the ability of the oocyte to reach the blastocyst stage) [5] [6] [7] [8]. "
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    ABSTRACT: The aim of this study was to evaluate the association between plasma anti-Mullerian hormone (AMH) concentration and in vitro embryo production (IVP) from Bos taurus (Holstein) and Bos indicus (Nelore) donors. A total of 59 Holstein (15 prepubertal heifers aged 8-10 mo, 15 cyclic heifers aged 12-14 mo, 14 lactating cows and 15 non-lactating cows) and 34 Nelore (12 prepubertal heifers aged 10-11 mo, 10 prepubertal heifers aged 21-23 mo and 12 cyclic heifers aged 24-26 mo) females were enrolled. All females underwent an ovum pick–up (OPU), without previous synchronization of the follicular wave, and IVP procedure. Immediately before the OPU procedure, blood samples were collected for subsequent AMH determination. A positive correlation was observed between the plasma AMH and number of in vitro embryos produced from Holstein (r = 0.36, P < 0.001) and Nelore (r = 0.50, P = 0.003) donors. For additional analyses, donors within each genotype were classified into 1 of 2 AMH categories (low or high) according to the average AMH concentration for each genotype. The results revealed that females classified as having high AMH presented a greater number of visible aspirated follicles (Holstein: 20.9 ± 1.5 vs. 13.6 ± 0.9, P < 0.0001; Nelore: 54.3 ± 6.1 vs. 18.6 ± 2.1, P < 0.0001) and a greater number of recovered cumulus-oocyte complexes (COC; Holstein: 17.3 ± 1.5 vs. 9.0 ± 0.9, P < 0.0001; Nelore: 45.3 ± 6.4 vs. 13.4 ± 1.7, P < 0.0001). However, there was no difference in the blastocyst production rate (Holstein: 20.6 ± 4.0 % vs. 19.8 ± 4.2 %, P = 0.60; Nelore: 33.7 ± 6.5 % vs. 27.4 ± 5.5 %; P = 0.41, high and low AMH, respectively). Moreover, donors classified as having high AMH yielded a greater number of embryos produced per OPU (Holstein: 3.0 ± 0.7, Nelore: 7.0 ± 1.7) compared to those classified as having low AMH (Holstein: 1.2 ± 0.3, P = 0.04; Nelore: 2.2 ± 0.5, P = 0.007). In conclusion, even though the plasma AMH concentration did not alter the ability of the COC to reach the blastocyst stage, the AMH concentration in plasma can be an accurate endocrine marker for the in vitro embryo yield from either Bos taurus (Holstein) or Bos indicus (Nelore) donors. Therefore, AMH is a promising tool to enhance the overall efficiency of OPU-IVP programs in the field as a selective criterion for high embryo producing donors.
    Domestic Animal Endocrinology 10/2014; 49(1). DOI:10.1016/j.domaniend.2014.07.002 · 2.17 Impact Factor
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    • "However, oocyte quality has been considered an important factor [1] [2] [3] [4] contributing to the low fertility reported for high producing lactating dairy cattle [5]. In addition, regardless the significant variation within animal [6] [7], IVP efficiency has been reported to be lower in lactating Holstein cattle as compared with Holstein heifers [8] and beef cattle [9]. Therefore, further studies are required to evaluate alternative strategies to improve the efficiency of IVP in Holstein donors, especially those that are lactating. "
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    ABSTRACT: The present study evaluated the efficacy of superstimulation with p-FSH (Folltropin) before the ovum pick-up (OPU) on IVP in lactating and nonlactating Holstein donors. A total of 30 Holstein cows (15 lactating and 15 nonlactating) were blocked by lactation status to one of two groups (control or p-FSH), in a cross-over design. On a random day of the estrous cycle, all cows received an intravaginal progesterone device and 2.0 mg IM of estradiol benzoate (Day 0). Cows in the control group received no further treatment, whereas cows in the p-FSH group received a total dosage of 200 mg of p-FSH on Days 4 and 5 in four decreasing doses 12 hours apart (57, 57, 43, and 43 mg). On Day 7, the progesterone device was removed, and OPU was conducted in both groups (40 hours after the last p-FSH injection in the p-FSH-treated group). There was no difference between groups (P = 0.92) in the numbers of follicles that were aspirated per OPU session (17.2 ± 1.3 vs. 17.1 ± 1.1 in control and p-FSH-treated cows, respectively); however, p-FSH-treated cows had a higher (P < 0.001) percentage of medium-sized follicles (6-10 mm) at the time of the OPU (55.1%; 285/517) than control cows (20.8%; 107/514). Although recovery rate was lower (60.0%, 310/517 vs. 69.8%, 359/514; P = 0.002), p-FSH-treated cows had a higher blastocyst production rate (34.5%, 89/258 vs. 19.8%, 55/278; P < 0.001) and more transferable embryos per OPU session were produced in the p-FSH group (3.0 ± 0.5 vs. 1.8 ± 0.4; P = 0.02). Regardless of treatment, non-lactating cows had a higher blastocyst rate (41.9%, 106/253 vs. 13.4%, 38/283; P = 0.001) and produced more transferable embryos per OPU session (3.5 ± 0.5 vs. 1.3 ± 0.3; P = 0.003) than lactating cows. Thus, superstimulation of Holstein donors with p-FSH before OPU increased the efficiency of IVP. In addition, non-lactating donors had higher percentage of in vitro blastocyst development and produced more embryos per OPU session than lactating cows.
    Theriogenology 04/2014; 82(2). DOI:10.1016/j.theriogenology.2014.04.013 · 1.80 Impact Factor
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