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Abstract The in vitro production of embryos by ovum pickup (OPU) and intracytoplasmic sperm injection (ICSI) is gaining popularity among horse breeders and veterinarians. Various collection media are available for flushing follicles during OPU. The objective of this study was to determine whether the type of flushing media used to aspirate follicles and collect oocytes influences the outcome of a commercial equine OPU-ICSI program. Two commercial embryo flushing media (EFM1 and EFM2) supplemented with heparin were compared with a flushing media designed specifically for the collection of oocytes (oocyte flushing media [OFM]) on the outcome of OPU-ICSI parameters in 234 Warmblood mares. The OPU-ICSI performed in mares using one of the EFM1 resulted in a lower (P <.05) blastocyst rate and blastocysts per OPU-ICSI session (11.9 ± 13.2%, 0.88 ± 1.3) than the OFM (19.2 ± 15.2%, 1.24 ± 1.2). Unlike the EFM2 solution, the heparin used to prepare the EFM1 contained preservatives including benzyl alcohol, a component known to alter the oocyte membrane, which might have been responsible for the lower developmental competence of oocytes collected with EFM1. In conclusion, exposure of oocytes (<1.5 hours) to one of the flushing medium tested in this study affected negatively the outcome of the OPU-ICSI commercial program when compared with flushing media designed for collection of equine oocytes. Care should be taken when choosing the components of the flushing media used to collect oocytes. Further research should be carried out to confirm the potential negative effect of the preservatives used in multidose heparin vials. Highlights • The type of flushing medium used during ovum pickup may affect oocyte developmental potential. • One of the tested flushing media resulted in a reduction of blastocyst rate and number of blastocysts per mare. • The medium with reduced blastocyst production was supplemented with heparin containing preservatives. [ABSTRACT FROM AUTHOR]

Introduction: Glucose is the primary energy substrate for early conceptus development and, for the first 40 days of gestation, the equine conceptus depends solely on glucose available in the histotroph; thereafter, histotrophic glucose provision continues to support transport across the definitive placenta.Methods: To investigate glucose provision routes during early equine pregnancy we examined expression of glucose transporters in conceptus membranes and endometrium recovered on days 7, 14, 21 and 28 after ovulation. To further differentiate the contributions of maternal progesterone priming and conceptus-endometrium crosstalk in regulating glucose transporter expression, day 8 embryos were transferred to recipient mares on day 8 (synchronous) or day 3 (asynchronous) after ovulation; conceptuses and endometrium were recovered 6 or 11 days later.Results: The glucose transporters SLC2A1, 2A3, 2A4, 2A8, 2A10 and 5A1 were expressed in equine endometrium. In conceptus membranes, expression of SLC2A1-3, 2A5, 2A8, 2A10, 5A1 and 5A11 increased from day 14, and SLC2A1 protein was highly abundant on the apical trophectodermal membrane and in the endoderm. Asynchronous embryo transfer (ET) resulted in reduced SLC2A1 expression in both the endometrium and conceptus membranes.Discussion: A wide range of glucose transporters are expressed in the pre-implantation equine conceptus and endometrium, presumably to ensure adequate glucose provision to the developing embryo. Endometrial expression of SLC2A1 appears to be regulated by a combination of progesterone-priming and conceptus signalling, and its delayed upregulation after asynchronous ET may contribute to the observed delay in conceptus development. [ABSTRACT FROM AUTHOR]

Introduction: Placental imprinted genes appear to be sensitive indicators of an inappropriate pre-implantation environment. This study examined the effects of negative uterine asynchrony after embryo transfer (ET) on early horse embryo development, and yolk-sac membrane expression of DNA methyltransferases (DNMTs) and equine specific placental imprinted genes.Methods: Day 8 embryos were transferred to recipient mares on day 8 (synchronous) or day 3 (asynchronous) after ovulation, and conceptuses were recovered 6 or 11 days later (day 14 or 19 of development).Results: Day 14 conceptuses recovered from an asynchronous uterus had a smaller embryonic disc, in which primitive streak development was visibly retarded compared to conceptuses from a synchronous uterus. Similarly, length, somite number and organogenesis were retarded in day 19 embryos after asynchronous ET. Maternal (GRB10, H19, IGF2R, PHLDA2) and paternal (IGF2, INSR, PEG3, PEG10, DIO3, NDN, SNRPN) imprinted genes and DNMTs (DNMT1, 3A and 3B) were all up-regulated between day 14 and 19 of pregnancy and, for most, mRNA expression was higher in synchronous than asynchronous day 19 yolk-sac membrane. Expression of the paternally imprinted gene HAT1 increased between day 14 and 19 of pregnancy, but was not affected by the asynchrony.Discussion: Conceptus development and upregulation of DNMTs and imprinted genes were delayed rather than dysregulated after transfer into a negatively asynchronous uterus. We propose that this ability to 'reset' conceptus development to uterine stage is an adaptation that explains why horse embryos are unusually tolerant of asynchrony after ET. [ABSTRACT FROM AUTHOR]

Some stallions used for both breeding and show jumping perform less well in competitions during the breeding season. It has been suggested that the demands of semen collection on the back and pelvis may impair the range of motion (ROM) required for show jumping. To better understand hindquarter dynamics, this study assessed the ROM of the hindquarters during both the mounting phase (MP) and ejaculatory phase (EP) of semen collection and compared it to the ROM previously measured during show jumping. The kinematics of six warmblood stallions were studied during semen collection on a phantom. Skin markers were placed on the withers, tuber coxae, proximal femur and tibia, and distal tibia and metatarsus. During each phase, six angles were measured using recordings made with a home-video camera (60 Hz) positioned perpendicular to the phantom. The differences in joint angles between the two phases were compared statistically using commercially available software. The pelvis showed a significantly larger ROM during the MP than the EP ( P < .05). The ROM of the hindquarters was significantly larger during both the MP and EP than reported during show jumping, and the pelvis was considerably more extended ( P < .05). This relatively extreme flexion and extension of the pelvis during semen collection may impose different strains on musculoskeletal structures which, combined with asymmetrical lateral flexion and/or axial rotation on the phantom, may exacerbate subclinical hindquarter pain. Nevertheless, the outcome of this study would benefit from an additional, objective clinical locomotor examination combined with analysis of motion during show jumping using modern IMU sensor technology. [ABSTRACT FROM AUTHOR]

The location of an undescended testicle influences the choice of surgical technique for efficient cryptorchid castration. We review a standardized protocol for preoperative examination to dictate surgical approach to cryptorchidism. Cases are split into two periods: 2004–2006 and 2007–2014. In 2004–2006, conventional cryptorchidectomy and laparoscopic cryptorchid castration (standing) were both offered, but the choice of technique was based primarily on owners' preference for a recumbent or standing procedure. In 2007–2014, ultrasonography was used to locate the testes and dictate the preferred surgical approach; for abdominal testes, laparoscopic intraabdominal spermatic cord ligation without orchidectomy was preferred and for inguinal testes, conventional open orchidectomy. The numbers of animals requiring a second procedure to complete castration were compared between the two periods. In addition, failure rates for individual testes grouped by location were determined separately for the different techniques, and the value of preoperative ultrasonography to locate the retained testes was assessed. In 2004–2006, 15.3% (20/131) of the cryptorchids needed more than one surgery to complete castration, compared to 0.7% (1/144) in 2007–2014. Failure rates for laparoscopic castration were 0/168 (0%) for abdominal, 3/40 (7.5%) for inguinal, and 9/55 (16.4%) for scrotal testes; for conventional castration, failure was recorded for 3/12 (25%) abdominal and 0/92 (0%) inguinal testes. For 94% (156/166) of retained testes, ultrasound-based preoperative advice on surgical approach was correct. Using a standardized preoperative examination to determine choice of surgical technique significantly ( P < .001) reduced the number of second surgeries needed to complete castration. Preoperative ultrasound is therefore a useful aid to determining the surgical approach to cryptorchid castration. [ABSTRACT FROM AUTHOR]

Conventional in vitro fertilization is poorly successful with equine gametes. Although stallion spermatozoa bind to the zona pellucida in vitro, they fail to acrosome react and cannot therefore penetrate into the perivitelline space. Failed sperm penetration most likely relates to the absence in in vitro fertilization media of essential molecules required to fully support stallion sperm capacitation. In vivo, the oviductal lumen provides an environment that appropriately regulates interactions between the gametes and promotes fertilization. Identifying the oviductal “fertilization stimulating factors” would enormously benefit the development of equine in vitro fertilization media. This review focuses on the current understanding of equine sperm–oviduct interactions, which may hold essential clues to achieving successful in vitro fertilization with equine gametes. [ABSTRACT FROM AUTHOR]