British Breeder Magazine May 2021

More documents

Recommendations

Info

Feature Article - Rossdales Ultrasound of the broodmare: what is your vet looking for? By Camilla Scott BVetMed, CertAVP(ESM), DACT, MRCVS RCVS Recognised Specialist in Veterinary Reproduction (Equine), Rossdales Veterinary Surgeons The major indication for transrectal ultrasound examination of your broodmare is for monitoring follicular development during oestrus to determine the optimum time for breeding and subsequent pregnancy diagnosis. However, ultrasound also provides rapid and accurate diagnosis of many other conditions in the mare. Growth and development of ovarian follicles In conjunction with palpation, ultrasound examination of the ovaries to track follicular growth and development is vital to determine the best time to breed for maximal fertility. Follicles will typically increase in diameter by 3-5mm per day, reaching maximal diameter 1 to 2 days prior to ovulation (release of the oocyte/egg for subsequent fertilisation). The size of an ovulatory follicle will vary depending on the mare’s breed and age, the time of year and the number of dominant follicles present, but ranges between 30-50mm. In the hours before ovulation, the dominant follicle changes from a regular spherical structure to an irregular shape and becomes softer with a thickened wall. More recently, the use of colour-doppler ultrasound can determine blood flow and perfusion changes in the maturing follicle, giving us further information to help predict ovulation. These ultrasound characteristics of the dominant follicle in the hours prior to ovulation are particularly critical when lining mares up for frozen semen breeding, to ensure insemination is performed within 6 hours of ovulation to maximize the chances of conception. A percentage of follicles will not ovulate appropriately but instead fill with blood. These follicles are termed hemorrhagic anovulatory follicles and are reported to occur in 5-20% of cycles in the early and late breeding season respectively. Ultrasound characteristics of these follicles initially include an excessive amount of free-floating bright white particles in the follicular fluid and then progresses as blood clots and fibrin strands develop, giving the anovulatory follicle a cobweb like appearance. Figure 1: Ultrasound examination of a mare lining up for breeding with a large dominant follicle. Figure 2: Ultrasonographic image of a dominant follicle with an irregular shape and thick wall prior to ovulation. Figure 3: Ultrasonographic image of a hemorrhagic anovulatory follicle filled with blood clots and fibrin strands. Is the degree of uterine oedema appropriate? Uterine edema is a normal response to hormone (oestradiol) secretion when a mare is in season and will gradually increase in line with development of the dominant follicle. Mares in oestrus will display a characteristic ‘sliced orange’ or ‘spoke wheel’ appearance on cross-sectional ultrasound examination of the uterus. Scoring systems have been developed to monitor the degree of uterine edema, typically ranging from 0 (typical of mares not in season) to 3 (peak uterine edema seen during oestrus). Estradiol secretion and maximal uterine edema usually peak 1 to 2 days prior to ovulation, with a subsequent decrease in estradiol reflected by a synchronous decrease in uterine edema on ultrasound examination, both of which help guide timings for administration of an ovulation induction agent and an appropriate time for breeding. Excessive or inappropriate uterine edema patterns may indicate an underlying inflammatory or infectious process. Mares with excessive uterine edema prior to breeding are at risk of subsequent intrauterine fluid accumulation and are likely to require further treatment such as uterine lavage and drugs to aid uterine clearance, such as oxytocin. Figure 4: Ultrasonographic image of a cross-section of the uterus depicting mild uterine edema (note characteristic appearance similar to a sliced orange segment), consistent with a mare in early estrus. Inadequate uterine drainage There are numerous potential causes for inappropriate intrauterine fluid accumulation in the mare. Risk factors include older multiparous mares with poor perineal conformation, older maiden mares with failure of cervical dilation, mares with an inadequate immune response and the use of frozen semen insemination. It is normal for all mares to have a degree of inflammation following breeding, but this transient endometritis should resolve within 24h in resistant mares, so any fluid beyond 36h is abnormal and needs attention. Ultrasound evaluation of uterine fluid accumulation in the problem mare is incredibly useful for both diagnosis and monitoring response to treatment. Figure 5: Ultrasonographic image of abnormal fluid accumulation within the uterus. 56 | BRITISH BREEDER
Corpus Luteum Following collapse of the dominant follicle and release of the oocyte/egg, a corpus luteum (CL) forms. The CL secretes progesterone, the dominant hormone of dioestrus (14 day period when the mare is not in season). If the mare becomes pregnant, progesterone secretion from the primary and secondary CLs will prevent the mare coming back into season and maintain the pregnancy until placental takeover at around 100-120 days of gestation. Ultrasound examination provides visual and objective evaluation of both the structural and functional aspects of development of the CL from maturation to regression. Evaluating and ageing the CL gives us essential information regarding the stage of the mare’s cycle, and more recently has been used for selection of recipient mares for embryo transfer both of fresh and ICSI produced embryos, when knowing the exact age of the CL/ number of days post ovulation is essential for a successful transfer. Figure 6: Ultrasonographic image of an ovary depicting two corpus luteum (CLs) following double ovulation. Uterine cysts Whilst the majority of uterine cysts are insignificant findings in older mares, their presence in the uterus may signify underlying issues. In addition, large or numerous cysts or those located at the base of the uterine horns may physically inhibit embryo mobility and fixation, resulting in failure of maternal recognition of pregnancy and early embryonic loss. Noting the size, number and location of cysts on ultrasound examination will help determine their potential significance; furthermore, mapping of cysts will also prevent any confusion over subsequent pregnancy diagnosis. Figure 7: Ultrasonographic image of a uterine cyst - note the irregular outline and fluid-filled centre. Early pregnancy diagnosis Ultrasound examination is pivotal for pregnancy diagnosis in mares. The equine embryo enters the uterus on day 5.5-6 post ovulation and can be detected via ultrasound examination from as early as 10 days post ovulation. Since, however, at this stage the embryonic vesicle measures only between 3-5mm, most first pregnancy scans are performed at 14 days post Feature Article - Rossdales ovulation, at which stage the embryonic vesicle typically measures between 16-20 mm, making it much easier to identify. Due to the unique equine embryonic capsule, the pregnancy will be perfectly spherical at this stage and ultrasonically generated specular reflections (bright white spots on the upper and lower surface of the embryo; see image) help differentiate embryos from uterine cysts or fluid, which are rarely perfectly spherical. Since mares are not able to carry twin pregnancies successfully to term, the diagnosis of twin pregnancies and subsequent reduction to a singleton pregnancy is performed most successfully at this early pregnancy scan, between 14-16 days post ovulation. Further pregnancy examinations are performed at regular intervals to monitor growth and development of the embryo/foetus. By day 21 the embryo proper can be visualised and at 28 days an embryonic heartbeat will be detectable. From 40 days onwards, the pregnancy enters the foetal stage of development (the term embryo is used until day 39), at a 42 day scan the start of the umbilical cord formation and the beginning of foetal activity can be detected. For those of you wanting to determine the gender of your foal, this can be reliably performed by transrectal ultrasound examination between 58-70 days post ovulation. Ultrasound detection of the genital tubercle, the precursor to the penis in the male and clitoris in the female is either detected under the tail in the case of a filly foal or behind the umbilicus with a colt foal. www.rossdales.com LEADERS IN EQUINE REPRODUCTIVE SERVICES ✔ Artificial insemination with fresh, chilled and frozen semen ✔ Embryo transfer ✔ OPU and shipping for ICSI ✔ Infertility Investigations ✔ Semen collection, evaluation, distribution and freezing ✔ World class hospital facilities and specialist expertise ✔ Neonatal intensive care unit ✔ State of the art laboratory, HBLB approved for CEM testing Contact our BEVA approved team of dedicated stud vets to discuss your requirements on 01638 663150, or practice@rossdales.com ROSSDALES VETERINARY SURGEONS, Beaufort Cottage Stables, High Street, Newmarket, CB8 8JS www.rossdales.com BRITISH BREEDER| 57
Page 1 and 2:
BRITISH BREEDER May 2021 The Brexit
Page 3 and 4:
May Issue - Index Welcome from the
Page 5 and 6: News British Equestrian EHV-1 updat
Page 7 and 8: Maximise FOR STALLIONS Address Moti
Page 9 and 10: News - Obituries Prince Philip, Duk
Page 11 and 12: News - Obituries Sir Shutterfly Lea
Page 13 and 14: News - Brexit Receiving Semen from
Page 15 and 16: START PREGNANCY BIRTH START STRONG
Page 17 and 18: British Breeding - Futurity & Equin
Page 19 and 20: Studbook - News Thoroughbred and Ar
Page 21 and 22: FUTURE IN MIND From the foals of Mo
Page 23 and 24: Studbook - News Sport Horse Breedin
Page 25 and 26: Studbook - News Buzz Lightyear (in
Page 27 and 28: Avant Techno (UK) Ltd sales@avant.c
Page 29 and 30: Studbook - News Organisation (WAHO)
Page 31 and 32: Features - Nasta Inside NaStA by Vi
Page 33 and 34: Studbook - News BRITISH BREEDER| 33
Page 35 and 36: The best approach to managing a foa
Page 37 and 38: Breeder Spotlight - Breen Equestria
Page 39 and 40: Breeder Spotlight - Breen Equestria
Page 41 and 42: Classic Opera & Churchill III Churc
Page 43 and 44: Feature Article - DNA DNA-Testing i
Page 45 and 46: Feature Article - DNA Nevertheless,
Page 47 and 48: Feature Article - PSSM2 available f
Page 49 and 50: Industry leaders in Equine Reproduc
Page 51 and 52: Nutrition Feature - Spillers Feeds
Page 53 and 54: Feature Article - Westgate Labs Why
Page 55: Cavalor Colostra From - cavalordire
Page 59 and 60: MOLENKONING IS THE WORLDS LEADING M
show all

British Breeder Magazine May 2021

Create successful ePaper yourself

Delete template?

Save as template?