TOTAL EAR CANAL ABLATION AND LATERAL BULLA OSTEOTOMY (TECA-LBO) IN ATLANTIC HARBOR SEALS (PHOCA VITULINA CONCOLOR) FOR SUCCESSFUL SURGICAL MANAGEMENT OF OTITIS MEDIA.

Chronic, severe otitis media was diagnosed in four Atlantic harbor seals (Phoca vitulina concolor), three of which were stranded animals undergoing rehabilitation. All seals presented with unilateral purulent aural discharge that would intermittently recur despite prolonged topical and systemic antimicrobial therapy. Aerobic culture from aural discharge isolated multidrug-resistant organisms in all seals, including Pseudomonas aeruginosa, Staphylococcus pseudintermedius, Klebsiella pneumoniae, and/or Enterococcus faecalis. Computed tomography was used in three cases to confirm otitis media and positive contrast ear canalography was used in one case to confirm tympanic membrane rupture. Given the persistent nature of otitis, surgical intervention in the form of a total ear canal ablation and lateral bulla osteotomy (TECA-LBO) was indicated. Surgery was successful in achieving complete clinical resolution of otitis in all seals. Postoperative complications included temporary unilateral paralysis of the left nare (2/4) and a transient left ptosis (1/4). Partial to complete surgical site dehiscence occurred in all cases; however, complete healing was achieved by second intention in 60 d or less. One rehabilitated seal was fitted with a satellite tag that confirmed normal swimming and diving patterns post release. In harbor seals, TECA-LBO can be performed safely to treat persistent cases of otitis media and should be considered in cases of chronic otitis that are not responsive to medical management.

Pharmacologic ciliary body ablation for chronic glaucoma in dogs: A retrospective review of 108 eyes from 2013 to 2018.

OBJECTIVE: To evaluate the long-term outcome and efficacy of intravitreal injection of gentamicin and dexamethasone sodium phosphate (IVGD) or triamcinolone in end-stage glaucoma patients and determine pre-procedure prognostic indicators of success and post-operative complications. PROCEDURE: Medical records were reviewed for 108 dogs (108 eyes) treated with intravitreal gentamicin with or without dexamethasone sodium phosphate or triamcinolone for glaucoma between 2013 and 2018 with 3 months of minimum follow-up. Signalment and clinical findings, including type of glaucoma, pre-procedure intraocular pressure (IOP), chronicity, procedure protocol, and outcome were recorded. Success was defined as an intraocular pressure of ≤25 mm Hg at the time of last re-examination or no ocular hypotensive medications at 3 months or longer post-injection. RESULTS: The overall success rate for pharmacologic ablation was 95%. The success rate for dogs receiving no ocular hypotensive medications was 86%. Seventy-six eyes (70.4%) had primary glaucoma, and 32 eyes (29.6%) had secondary glaucoma. Age at the time of injection had no effect on initial success but did in final success (P =-.03) for dogs requiring repeat injections. Cocker Spaniels required the most repeat 2nd and 3rd injections (3/12 dogs) and (2/4 dogs), respectively. No preoperative variable significantly affected the success rate. The most common complications were phthisis bulbi (59.2%), corneal edema (25.9%), and ulcerative keratitis (22.3%). Uncontrolled IOP resulted in enucleation in two dogs (1.8%). CONCLUSIONS: Pharmacologic ablation has a high overall success rate in lowering IOP to ≤25 mm Hg short-term in blind, glaucomatous canine eyes. Type of glaucoma, pre-procedure IOP, chronicity, and protocol did not affect success.

Effects of fentanyl-lidocaine-ketamine versus sufentanil-lidocaine-ketamine on the isoflurane requirements in dogs undergoing total ear canal ablation and lateral bulla osteotomy.

OBJECTIVE: To compare the isoflurane-sparing effects of sufentanil-lidocaine-ketamine (SLK) and fentanyl-lidocaine-ketamine (FLK) infusions in dogs undergoing total ear canal ablation and lateral bulla osteotomy (TECA-LBO). STUDY DESIGN: Randomized blinded clinical study. ANIMALS: A group of 20 client-owned dogs undergoing TECA-LBO. METHODS: Intravenous (IV) administration of lidocaine (3 mg kg-1) and ketamine (0.6 mg kg-1) with fentanyl (5.4 µg kg-1; n = 10; FLK group) or sufentanil (0.72 µg kg-1; n = 10; SLK group) was immediately followed by the corresponding constant rate infusion (CRI) (lidocaine 3 mg kg-1 hour-1; ketamine 0.6 mg kg-1 hour-1; either fentanyl 5.4 µg kg-1 hour-1 or sufentanil 0.72 µg kg-1 hour-1). Anaesthesia was induced with propofol 3-5 mg kg-1 IV and was maintained with isoflurane. End-tidal isoflurane concentration (Fe'Iso) was decreased in 0.2% steps every 15 minutes until spontaneous movements were observed (treated with propofol 1 mg kg-1 IV) or an increase of > 30% in heart rate or mean arterial pressure from baseline occurred (treated with rescue fentanyl or sufentanil). Quality of recovery and pain were assessed at extubation using the short-form Glasgow Composite Pain Scale (SF-GCPS), Colorado State University Canine Acute Pain scale (CSU-CAP), and visual analogue scale (VAS). Data were analysed with analysis of variance, t tests, Fisher test and Spearman coefficient (p < 0.05). RESULTS: Fe'Iso decreased significantly in SLK group (45%; p = 0.0006) but not in FLK (15%; p = 0.1135) (p = 0.0136). SLK group had lower scores for recovery quality (p = 0.0204), SF-GCPS (p = 0.0071) and CSU-CAP (p = 0.0273) than FLK at extubation. Intraoperative rescue analgesia and VAS were not significantly different between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with FLK infusion, CRI of SLK at these doses decreased isoflurane requirements, decreased pain scores and improved recovery quality at extubation in dogs undergoing TECA-LBO.

Otoscopic evaluation of epithelial remnants in the tympanic cavity after total ear canal ablation and lateral bulla osteotomy.

OBJECTIVE: To determine the ability to detect the presence of epithelial remnants after total ear canal ablation (TECA) and lateral bulla osteotomy (LBO) with endoscopy and to identify the most common locations of epithelial remnants after tympanic curettage. STUDY DESIGN: Experimental study. ANIMALS: Five fresh canine cadavers with no gross evidence of middle ear disease. METHODS: Ten TECA-LBO were performed by four surgeons. After tympanic curettage, a 1.9-mm rigid 30° endoscope was inserted into the rostral, caudal, dorsal, ventral, and medial sections of the tympanic cavity. Three observers evaluated otoscopic images for epithelial remnants in each compartment. The median distribution of epithelial remnants was calculated for each section of the tympanic cavity with a three-dimensional tympanic cavity model. RESULTS: Epithelial remnants were identified in at least one of the five areas of the tympanic cavity after each TECA-LBO. The rostral section contained the most epithelial remnants (35.6%), while the medial section contained the least amount (1.8%). CONCLUSION: Use of a 1.9-mm rigid endoscope was an effective method to evaluate all sections of the tympanic cavity after curettage in TECA-LBO. Epithelial remnants were consistently found after TECA-LBO, especially in the rostral compartment. CLINICAL SIGNIFICANCE: Intraoperative endoscopy should be considered to improve removal of epithelium after initial TECA-LBO or revision surgeries.

High-Frequency Irreversible Electroporation for Treatment of Primary Liver Cancer: A Proof-of-Principle Study in Canine Hepatocellular Carcinoma.

PURPOSE: To determine the safety and feasibility of percutaneous high-frequency irreversible electroporation (HFIRE) for primary liver cancer and evaluate the HFIRE-induced local immune response. MATERIALS AND METHODS: HFIRE therapy was delivered percutaneously in 3 canine patients with resectable hepatocellular carcinoma (HCC) in the absence of intraoperative paralytic agents or cardiac synchronization. Pre- and post-HFIRE biopsy samples were processed with histopathology and immunohistochemistry for CD3, CD4, CD8, and CD79a. Blood was collected on days 0, 2, and 4 for complete blood count and chemistry. Numeric models were developed to determine the treatment-specific lethal thresholds for malignant canine liver tissue and healthy porcine liver tissue. RESULTS: HFIRE resulted in predictable ablation volumes as assessed by posttreatment CT. No detectable cardiac interference and minimal muscle contraction occurred during HFIRE. No clinically significant adverse events occurred secondary to HFIRE. Microscopically, a well-defined ablation zone surrounded by a reactive zone was evident in the majority of samples. This zone was composed primarily of maturing collagen interspersed with CD3+/CD4-/CD8- lymphocytes in a proinflammatory microenvironment. The average ablation volumes for the canine HCC patients and the healthy porcine tissue were 3.89 cm3 ± 0.74 and 1.56 cm3 ± 0.16, respectively (P = .03), and the respective average lethal thresholds were 710 V/cm ± 28.2 and 957 V/cm ± 24.4 V/cm (P = .0004). CONCLUSIONS: HFIRE can safely and effectively be delivered percutaneously, results in a predictable ablation volume, and is associated with lymphocytic tumor infiltration. This is the first step toward the use of HFIRE for treatment of unresectable liver tumors.

Effects of follicular ablation and induced luteolysis on LH and follicular fluid factors during the periovulatory period in mares.

Haemorrhagic anovulatory follicles (HAFs) are the most common pathological anovulatory condition in the mare. To enhance understanding of the physiopathology of HAFs, the aim of the present study was to determine the effects of an induced-follicular wave on LH concentrations and follicular fluid factors relevant to the ovulatory process. Mares were allocated to treatment or control groups (n = 7/group) in a crossed over design during 14 oestrous cycles with a period of one cycle occurring when there were no treatments between the times when treatments were administered. In the treatment group, all antral follicles ≥8 mm were ablated on Day 10 after ovulation followed by administration of a luteolytic dose of PGF2α. All mares of both groups were treated with 1500 IU of hCG when a follicle ≥32 mm was detected (Hour 0), and follicular fluid was aspirated 35 h later. Blood samples were collected every 48 h from Day 10 until Hour 0 from all mares. Follicular fluid was assayed for PGE2, estradiol and progesterone. Plasma was assayed for LH concentrations. A follicular wave followed follicle ablation in the treated mares. Concentrations of LH were greater (P = 0.05) in mares ot the treatment compared with control group. Concentrations of PGE2, estradiol and progesterone in follicular fluid did not differ between groups (P > 0.05). Treatment resulted in an earlier increase in circulating LH, however, there was no effect on concentrations of intra-follicular PGE2, estradiol or progesterone in hCG-stimulated preovulatory follicles.

Veterinary Clinics: Tumor Ablation.

Over the past decade, interventional oncology techniques have become integrated into the treatment plans of companion animals with cancer on a regular basis. Although procedures such as stenting are performed commonly, other less frequently utilized techniques for locoregional therapy, such as embolization and ablation, are emerging and demonstrating promise. Tumor ablation techniques are categorized into two subgroups: chemical ablation and energy-based ablation. Increased utilization of ablation will allow for the determination of specific indications and evaluation of outcomes for these techniques.

Video-assisted microwave ablation for the treatment of a metastatic lung lesion in a dog with appendicular osteosarcoma and hypertrophic osteopathy.

OBJECTIVE: To describe video-assisted microwave ablation (VAMA) for the treatment of a metastatic lung lesion secondary to right forelimb osteosarcoma in a dog. STUDY DESIGN: Case report. ANIMALS: A 10-year-old female spayed mixed breed dog with a metastatic lung lesion secondary to appendicular osteosarcoma. METHODS: An osteosarcoma of the right distal scapula and proximal humerus that was suspected to be a radiation-induced osteosarcoma was treated with limb amputation and carboplatin chemotherapy. The patient developed pulmonary metastatic lesions and hypertrophic osteopathy (HO). VAMA of a metastatic lesion in the right caudal lung lobe was performed 227 days after amputation. The procedure was performed without complication. RESULTS: Follow-up information with the referring veterinarian 40 days after VAMA indicated that the patient was stable and that the clinical signs of HO had resolved. Thoracic radiographs taken by the referring veterinarian (RDVM) at monthly intervals showed that the previously treated metastatic lesion was stable. At 134 days from VAMA, the patient presented to the RDVM for lethargy and dyspnea and was transferred to an emergency clinic. The patient arrested and died 136 days from the VAMA procedure while hospitalized. A postmortem was not performed. CONCLUSION: VAMA for pulmonary metastatic lesions is technically feasible and allows for the treatment of symptoms associated with HO and minimally invasive management of pulmonary metastases in the case reported.

Outcomes for dogs with primary hyperparathyroidism following treatment with percutaneous ultrasound-guided ethanol ablation of presumed functional parathyroid nodules: 27 cases (2008-2011).

OBJECTIVE: To describe outcomes for dogs with primary hyperparathyroidism following treatment with percutaneous ultrasound-guided ethanol ablation of presumed functional parathyroid nodules. DESIGN: Retrospective case series. ANIMALS: 24 dogs with primary hyperparathyroidism that underwent 27 ultrasound-guided ethanol ablation procedures of presumed functional parathyroid nodules identified by cervical ultrasonography. PROCEDURES: Dogs were anesthetized for each procedure. For each nodule, 95% ethanol was injected into the center with ultrasound guidance (volume injected calculated on the basis of ultrasonographic measurements). The interval from treatment to resolution of hypercalcemia, complications, and follow-up clinicopathologic data were recorded. RESULTS: 5 procedures involved simultaneous treatment of 2 nodules. Three dogs underwent a second treatment because of initial treatment failure or development of another nodule. Hypercalcemia resolved after 23 of 27 (85%) procedures. In those 23 treatments, 22 (96%) had resolution of hypercalcemia within 72 hours after treatment. Hypocalcemia was detected in 6 different dogs at 2 (1 dog), 7 (3 dogs), 14 (1 dog), and 21 (1 dog) days after treatment; 5 of these dogs had mild transient hypocalcemia and 1 developed clinical signs requiring calcium supplementation. Although there were no periprocedural adverse effects, 2 dogs had delayed adverse effects; the overall rate of complications (including delayed adverse events and clinical hypocalcemia) was 11.1%. Long-term follow-up data indicated sustained normocalcemia in 17 of 19 dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that percutaneous ultrasound-guided ethanol ablation of functional parathyroid nodules may be an effective treatment for primary hyperparathyroidism of dogs, with short duration of anesthesia, minimal complications, and low risk for hypocalcemia.

The carbon dioxide laser: an alternative surgery technique for the treatment of common cutaneous tumors in dogs.

BACKGROUND: Tumors of the skin and subcutaneous tissue are the largest group of canine neoplasms. Total excision is still the most effective method for treatment of these skin tumors. For its universal properties the carbon dioxide (CO2) laser appears to be an excellent surgical instrument in veterinary surgery. Laser techniques are alternatives to traditional methods for the surgical management of tumors. The aim of this study was to compare various types of laser techniques in skin oncologic surgery: excision, ablation and mixed technique and to suggest which technique of CO2 laser procedure is the most useful in particular case of tumors in dogs. FINDINGS: The study was performed on 38 privately-owned dogs with total number of 40 skin tumors of different type removed by various CO2 laser operation techniques from 2010-2013. The treatment effect was based on the surgical wound evaluation, the relative time of healing and possible local recurrence of the tumor after 3 months post surgery. Local recurrence was observed in two cases. The study showed that in 30 cases time needed for complete resection of lesions was less than 10 minutes. Time of healing was longer than 12 days in 6 cases (42.8%) with tumor excision and in 14 cases (87.5%) where excision with ablation technique was performed. CONCLUSIONS: The advantages of the CO2 laser surgery were better hemostasis, precision of working, non-contact dissection, less instruments at the site of operation and minimum traumatization of the surrounding tissues.

Ovarian synchronisation in wood bison (Bison bison athabascae) during the anovulatory season.

Two experiments were performed in wood bison during the anovulatory season to establish an effective protocol for ovarian synchronisation. In an untreated control phase, bison cows (n=19) were examined daily to establish the interval to new follicular wave emergence (4.9±0.7 days) for the purposes of comparison with the experimental treatments. In Experiment 1, bison were treated by transvaginal ultrasound-guided follicular ablation (n=9) or with 2mg, i.m., 17ß-oestradiol (n=10). In Experiment 2, bison were treated by follicular ablation (n=9) or with 2mg, i.m., 17ß-oestradiol +100mg, i.m., progesterone (n=10). In Experiment 1, the interval to new wave emergence for control, follicular ablation and 17ß-oestradiol-treated groups was 4.9±0.7, 1.1±0.1 and 3.1±0.4 days, respectively (P<0.05). The degree of synchrony was 2.4±0.4, 0.2±0.1 and 0.8±0.2 days, respectively (P<0.05). In Experiment 2, the interval to new wave emergence for control, follicular ablation and 17ß-oestradiol + progesterone-treated groups was 4.9±0.7, 1.2±0.2 and 3.3±0.3 days, respectively (P<0.05), and the degree of synchrony was 2.4±0.4, 0.2±0.1, and 0.8±0.2 days, respectively (P<0.05). The degree of synchrony did not differ between ablation and hormone treatment groups in either experiment, but was greater in treatment groups than in the untreated control phase. Both follicular ablation and hormone treatment shortened and decreased the variability in the interval to follicular wave emergence in bison, but wave emergence occurred earlier after follicular ablation.

MRI findings of a middle ear cholesteatoma in a dog.

This article describes the MRI features of a middle ear cholesteatoma in an 8 yr old flat-coated retriever. Physical examination revealed pain on opening the jaw, and otoscopic examination showed tympanic membrane rupture associated with hyperplastic tissue at the entrance of the middle ear. Standard MRI sequences allowed for the identification of a severely expanded bulla containing material that was isointense to brain tissue on T1-weighted images and of mixed intensity on T2-weighted and fluid-attenuated inversion recovery sequences. No postcontrast enhancement of the content was present, but the lining of the bulla was partially enhanced. The images allowed evaluation of the surgical margins and the secondary changes due to the expansion of the mass. Surgery was performed and histopathology confirmed the presumptive diagnosis of cholesteatoma. In the present case, MRI appeared to serve as a good alternative to computed tomography for the diagnosis of cholesteatoma.

Unilateral ablation of follicles ≥ 4 mm leads to compensatory follicle response from the contralateral ovary in heifers.

In each of two experiments, heifers were assigned to a control group and a unilaterally ablated (UA) group (n = 6/group). In the UA group, follicles ≥ 4 mm in the left ovary were ablated by transvaginal ultrasound-guided technique at Hour 0 (8:00 AM) on the day of ovulation. Follicles in the CL-bearing right ovary remained intact. In Experiment 1, ablations continued until the next ovulation, and new follicles emerged in the right ovary in 9 of 14 (64%) waves. The number of follicles/wave (combined, 6.4 ± 0.4) did not differ between groups. In Experiment 2, follicles were counted at Hours 0, 4, 8, 12, and 24; the resistance index (RI) for blood flow in the ovarian pedicle was determined at Hours 0 and 12; and blood samples were collected every hour from Hours 0 to 12 and at Hour 24. An increase (P < 0.05) in the number of follicles in the follicle-intact ovary began at Hour 4 with complete compensation by Hour 24. Concentrations of FSH did not change between Hours 0 and 24 in the UA group but decreased (P < 0.05) in the controls by Hour 7. At Hour 12, RI to the right ovary approached being lower (P < 0.06) in the UA group than in the control group. Results indicated that unilateral ablation of follicles ≥ 4 mm led to compensatory follicle response in the follicle-intact ovary, and initially circulatory FSH concentrations were maintained and blood flow to the follicle-intact ovary increased.

Ovarian hydrobursitis in female camels (Camelus dromedarius): clinical findings, histopathology and fertility after unilateral surgical ablation.

This study was undertaken to verify the clinical signs, incidence, location, etiology and pathology of ovarian hydrobursitis in infertile female camels and estimate the fertility after unilateral surgical ablation. Genital organs (n = 124) were examined in camels slaughtered at Makkah abattoir during Hajj of 2009. Infertile female camels (n = 142) presented for management to the Veterinary Teaching Hospital, Qassim University, Saudi Arabia, were clinically examined and ultrasound-scanned for the diagnosis of genital abnormalities. Twenty eight camels diagnosed with ovarian hydrobursitis were further investigated for the effect of unilateral surgical ablation on breeding outcomes. Surgical ablation was carried on 14 cases (treated group), the remaining 14 cases were followed as controls (control group). Both groups were observed for breeding results: 90 days non-return rate (90d NRR) and calving rate (CR). Removed bursae were sent to the laboratory for histopathological investigation. Results showed that the incidence of ovarian hydrobursitis was 6.5% in slaughtered camels and 33.8% in infertile females. Camels with hydrobursitis were concurrently affected with pyometra, uterine and vaginal adhesions or purulent endometritis. Histopathology reported degeneration and hyperplasia of the lining epithelium, mononuclear cells infiltration, focal aggregation of inflammatory cells, cystic dilatation of multi-acinal structures, tiny hemorrhages, and presence of hemosiderin-laden macrophages. The 90d NRR and CR of the surgically-treated cases were 64.3% and 50%, respectively. None of the untreated cases conceived. These results confirmed that ovarian hydrobursitis causes infertility in dromedary female camels and is associated with inflammatory genital conditions and surgical ablation in unilaterally affected animals presents a potential treatment.

Non-thermal irreversible electroporation (N-TIRE) and adjuvant fractionated radiotherapeutic multimodal therapy for intracranial malignant glioma in a canine patient.

Non-thermal irreversible electroporation (N-TIRE) has shown promise as an ablative therapy for a variety of soft-tissue neoplasms. Here we describe the therapeutic planning aspects and first clinical application of N-TIRE for the treatment of an inoperable, spontaneous malignant intracranial glioma in a canine patient. The N-TIRE ablation was performed safely, effectively reduced the tumor volume and associated intracranial hypertension, and provided sufficient improvement in neurological function of the patient to safely undergo adjunctive fractionated radiotherapy (RT) according to current standards of care. Complete remission was achieved based on serial magnetic resonance imaging examinations of the brain, although progressive radiation encephalopathy resulted in the death of the dog 149 days after N-TIRE therapy. The length of survival of this patient was comparable to dogs with intracranial tumors treated via standard excisional surgery and adjunctive fractionated external beam RT. Our results illustrate the potential benefits of N-TIRE for in vivo ablation of undesirable brain tissue, especially when traditional methods of cytoreductive surgery are not possible or ideal, and highlight the potential radiosensitizing effects of N-TIRE on the brain.

Inducible male infertility by targeted cell ablation in zebrafish testis.

To generate a zebrafish model of inducible male sterility, we expressed an Escherichia coli nitroreductase (Ntr) gene in the male germ line of zebrafish. The Ntr gene encodes an enzyme that can convert prodrugs such as metronidazole (Met) to cytotoxins. A fusion protein eGFP:Ntr (fusing Ntr to eGFP) under control of approximately 2 kb putative promoters of the zebrafish testis-specific genes, A-kinase anchoring protein-associated protein (Asp), outer dense fibers (Odf), and sperm acrosomal membrane-associated protein (Sam) was expressed in the male germ line. Three independent and four compound transgenic zebrafish lines expressing eGFP:Ntr were established. Female carriers were fertile, while males exhibited different levels of sterility and appeared normal, otherwise. Developmental analysis shows that germ cells survived and testes were normal before Met treatment, but that the testes of all male transgenic zebrafish exhibited variously depleted prospermatogonia after Met treatment. Particularly in a triple-transgenic line, Tg(AOS-eGFP:Ntr)[Tg(Asp-eGFP:Ntr; Odf-eGFP:Ntr; Sam-eGFP:Ntr)], the transgenic males had very small testes that were virtually devoid of germ cells, and the residual germ cells had almost completely disappeared after 2 weeks of Met treatment. These zebrafish transgenic lines show the complete testis specificity of inducible male sterility after Met treatment and reveal a period of the Ntr/Met ablation activity just prior to formation of the definitive adult spermatogonial cell population. This study demonstrates that combined genetic and pharmacological methods for developing an "infertile breeding technology" have practical application in controlling genetically modified (GM) fish breeding and meet the standards of biological and environment safety for other GM species.

Ovulation synchrony after follicle ablation in mares.

Two experiments were performed to determine the efficacy of ultrasound-guided transvaginal follicle ablation for synchronizing ovarian function in mares. The experiments were initiated at random stages of the oestrous cycle in control (nonablated) and follicle-ablated mares. On day 0, all follicles > or =10 mm in diameter were punctured, aspirated and curettaged in ablated mares, and, on day 4, two doses of PGF2alpha were administered with a 12 h interval between the doses to both ablated and nonablated (control) mares. In Expt 1, hCG was administered to the ablated mares on the first or second day after the largest follicle was > or =30 mm in diameter. In Expt 2, hCG was administered to ablated mares 6 days after PGF2alpha administration, at which time the largest follicle was expected to be > or =30 mm in diameter. FSH concentrations increased initially and decreased subsequently in the ablated mares, and the ablation-induced wave (first detection of a follicle > or =10 mm in diameter) was observed 1.9 days after ablation and was synchronous (1-3 days) in 90% of mares. In both Expts 1 and 2, the uniformity of follicular wave emergence among follicle-ablated mares resulted in significantly better synchrony of ovulation after PGF2alpha administration compared with that of control mares. The variation in the interval from PGF2alpha administration to ovulation in ablated mares was reduced further by hCG administration. In the ablation + hCG groups, ovulation synchrony occurred 6-10 days after PGF2alpha administration in Expt 1 (13/16, 81%) and 7-8 days after PGF2alpha administration in Expt 2 (7/8, 88%). The extended period of ovulation in Expt 1 compared with that of Expt 2 (5 versus 2 days) was inherent in the experimental design, as hCG was not administered in Expt 1 until the largest follicle reached > or =30 mm in diameter, whereas in Expt 2 the experimental design was modified such that hCG was administered 6 days after PGF2alpha administration. As a result, in Expt 2 all but one mare in the ablation + hCG group ovulated within a 2 day period; 75% (6/8) ovulated on day 8 after PGF2alpha administration. Combined data from Expts 1 and 2 revealed that 96% (22/23) of the follicle-ablated mares ovulated within 48 h of hCG administration. Significantly more double ovulations were detected in follicle-ablated mares (10/41, 24%) than in control mares (1/21, 5%). The relatively high degree of ovulation synchrony obtained among mares in the present study indicates that this procedure can be used as an alternative method to synchronize ovarian function in horses.