Preovulatory follicle characteristics and oocyte competence in repeat breeder dairy cows

Abstract

The varied and elusive etiology of repeat breeding (RB) in dairy cows necessitates evaluation of oocytes and follicles, which have not previously been assessed together. Accordingly, we evaluated characteristics of preovulatory follicles and the competence of oocytes in control (CTL) and RB cows. The estrous cycles of 35 cows (18 CTL and 17 RB) were synchronized using PGF and estrus detection. Cows with a corpus luteum were treated with PGF and, 14 to 15 d after a visible behavioral estrus, they were administered a second PGF, followed 48 h later by follicular fluid (FF) aspiration of the preovulatory follicles. Estradiol (E)-active preovulatory follicles did not differ in diameter between the 2 groups of cows. However, FF of RB cows had higher E concentrations than that of CTL cows: 1,854.9 and 1,073.6 ng/mL, respectively, but similar androstenedione and progesterone concentrations. In the second part of the study, 14 consecutive ovum pick-ups (OPU) were performed in 5 CTL and 5 RB cows, at 3- to 4-d intervals. The RB and CTL cows did not differ in average numbers of follicles available per cow per session (7.1 and 7.3, respectively), oocyte recovery rates (42.2 and 44.1%, respectively), or cleavage rates (57.6 and 63.4%, respectively), but blastocyst production was markedly less in RB than in CTL cows (12.5 and 29.2%, respectively). We conclude that part of the RB cows' etiology occurs at an earlier phase of folliculogenesis, thereby impairing oocyte competence, and subsequently reducing the probability of normal fertilization, which diminish embryo vitality and development.

The incompletely fulfilled promise of embryo transfer in cattle—why aren’t pregnancy rates greater and what can we do about it?

“…The reason why ET improves fertility is unclear and causes of the repeat-breeder syndrome are likely to differ between individual cows and between herds of cows. Some causes of the repeat breeder syndrome, such as reduced oocyte quality ( Kurykin et al, 2011 ; Sood et al, 2017 ), would be expected to be alleviated by ET, whereas other causes, such as alterations in endometrial function ( Katagiri and Takahashi, 2004 ), would be reversible by ET only if the disorder was resolved after the day of transfer.…”

Management of Repeat Breeding Syndrome in Cows

“…Five out of 10 cows in the control group and six out of ten in the treated group had a repeat breeding syndrome which was influenced by the hormonal misbalance and incorrect timing of insemination, as they had no obvious reproductive pathology that could have represented the cause of RBS. Moreover, a recent study by Sood et al (2017) demonstrated that part of the RB cows' etiology occurs at an earlier phase of folliculogenesis, thereby impairing oocyte competence, and subsequently reducing the probability of normal fertilization, which diminish embryo vitality and development. Also, Kafi et al (2017) proved that the ovulatory follicle microenvironment of Holstein repeat breeder heifers places their oocytes at a developmental disadvantage, suggesting the existence of an inherent inferior quality of the ovulatory follicle microenvironment in repeat breeding Holstein heifers.…”

Improvement of fertility in repeat breeder dairy cattle by embryo transfer following artificial insemination: possibility of interferon tau replenishment effect

“…For example, the yield of oocytes and their quality from repeat breeder dairy cows was lower than that from healthy dairy cows [11, 13]. Moreover, after ovum pickups and IVF, blastocyst production was markedly lower in repeat breeder cows than in healthy control cows [10]. Interestingly, Kafi et al .…”

“…Some investigations found endocrine dysfunction in repeat breeder cattle, including higher levels of progesterone (P4) with low levels of estradiol during estrus, delayed luteinizing hormone surge and resulting in the aging of oocytes and abnormal fertilization, and a slow increase in P4 levels during the early luteal phase associated with low pregnancy rates [7,8,9]. It is also known that qualitative changes in oocytes and follicular fluids of repeat breeder cattle occur, and result in either fertilization failure or early embryonic death [10,11,12,13,14]. In addition, intrauterine cytokine regulatory mechanism disorder is one of the causes of repeat breeding.…”