Transvaginal ultrasound-guided pregnancy reduction (TUGR) is a procedure described for the management of twins post-fixation in the horse. Success rates are often disappointing but reported to be more favourable for bilaterally-situated twins, and when intervention takes place before day 35 of gestation. This study aimed to determine whether stabbing the embryo/fetus rather than aspirating conceptus fluids improved the likelihood of success, suggests that TUGR is not the method of choice for reducing > day 45 twins. Four pregnancy losses were recorded 1-7 months post-TUGR (4/38: 10.5%) and, while it is tempting to attribute the losses to TUGR, this rate of late gestation pregnancy loss is normal. We conclude that TUGR by fetal stabbing does not offer significant advantages over fluid aspiration.However, TUGR should be performed before day 35 of gestation and considered primarily a salvage procedure to be used when re-breeding is not a viable alternative.
Abstract. Advanced maternal age and in vitro embryo production (IVP) predispose to pregnancy loss in horses. We investigated whether mare age and IVP were associated with alterations in mitochondrial (mt) DNA copy number or function that could compromise oocyte and embryo development. Effects of mare age (,12 vs $12 years) on mtDNA copy number, ATP content and expression of genes involved in mitochondrial replication (mitochondrial transcription factor (TFAM ), mtDNA polymerase g subunit B (mtPOLB) and mitochondrial single-stranded DNA-binding protein (SSB)), energy production (ATP synthase-coupling factor 6, mitochondrial-like (ATP-synth_F6)) and oxygen free radical scavenging (glutathione peroxidase 3 (GPX3)) were investigated in oocytes before and after in vitro maturation (IVM), and in early embryos. Expression of TFAM, mtPOLB and ATP-synth-F6 declined after IVM (P , 0.05). However, maternal age did not affect oocyte ATP content or expression of genes involved in mitochondrial replication or function. Day 7 embryos from mares $12 years had fewer mtDNA copies (P ¼ 0.01) and lower mtDNA : total DNA ratios (P , 0.01) than embryos from younger mares, indicating an effect not simply due to lower cell number. Day 8 IVP embryos had similar mtDNA copy numbers to Day 7 in vivo embryos, but higher mtPOLB (P ¼ 0.013) and a tendency to reduced GPX3 expression (P ¼ 0.09). The lower mtDNA number in embryos from older mares may compromise development, but could be an effect rather than cause of developmental retardation. The general down-regulation of genes involved in mitochondrial replication and function after IVM may compromise resulting embryos.
Summary
A 13‐year‐old pluriparous Dutch Warmblood mare presented to Utrecht University's Department of Equine Sciences 4 weeks after suspected abortion at 3.5 months gestation, to investigate the nature of a uterine mass and persistent vulval discharge. Transrectal ultrasonographic examination revealed copious flocculent fluid and fetal remnants within the uterus and a 5–6 cm heterogenous mass in the uterine wall at the tip of the right horn. Expulsion of fetal parts and resolution of the coexisting endometritis were effected by a combination of repeated PGF2a analogue injections to induce oestrus, application of PGE2 gel to aid cervical relaxation, and daily uterine lavage and antibiotic instillation. The presence of the mass in the uterine wall was confirmed by hysteroscopy and the suspected tumour subsequently removed by partial laparoscopic ovariohysterectomy under standing sedation and local anaesthesia. The histological appearance of the tumour was consistent with a leiomyoma or moderately malignant leiomyosarcoma. Although a follow‐up examination 6 months post surgery revealed uncomplicated healing of the uterus, the owner decided to retire the mare from breeding. Uterine neoplasia is an extremely unusual cause of fetal death in the mare but, in the present case, laparoscopic partial ovariohysterectomy proved a promising, minimally invasive technique for salvaging sufficient uterus to make subsequent breeding a realistic proposition.
Cryopreservation caused more cellular damage to large embryos than smaller ones. While vitrification is more practical, it is not advisable for large embryos due to a higher incidence of dead cells. The choice is less obvious for small embryos, as vitrification led to occasionally very high percentages of dead or damaged cells, but a lower incidence of embryo disintegration. Modifications that reduce the level of cellular damage induced by vitrification are required before it can be considered the method of choice for cryopreserving equine embryos.
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