Estrous Behavior in Mules—An Owner's Perspective

GnRH Vaccine Could Suppress Serum Testosterone in Stallion Mules

Stallion mules have been used as working equids in several countries. Aggressiveness under the influence of testosterone results in the necessity for surgical castration before work training. The gonadotropin-releasing hormone (GnRH) vaccine may be an alternative method for immunocastration in mules. The objective of this study was to evaluate the effect of the GnRH vaccine on anti-GnRH antibody concentration, serum testosterone concentration, clinical adverse effects, and behavioral changes in response to receiving selected physical manipulations from humans. Twenty-five mules were separated into three groups: Control-intact, Control-castrated, and Treatment. The Treatment group was further divided according to condition (intact or unilateral cryptorchid) and age. The Treatment group received 195 µg of the GnRH vaccine intramuscularly at weeks 0, 4, and 8. The anti-GnRH antibody concentrations increased at weeks 6 and 10, and then they gradually decreased to baseline at week 24. The Treatment-intact-young group had the highest concentration of anti-GnRH antibody. The serum testosterone concentrations in the Treatment group were lower than before vaccination from weeks 6 to 14. Subcutaneous edema adjacent to the injection site was detected in the Treatment-intact group after booster vaccination. In conclusion, the mules responded to the GnRH vaccine, which could temporarily suppress testosterone for up to 14 weeks.

Behavioral Disorders in Mares with Ovarian Disorders, Outcome after Laparoscopic Ovariectomy: A Case Series

Owner complaints of estrus-related behavior in mares are a common cause of referral for laparoscopic ovariectomy. Granulosa cell tumors are a common neoplastic condition affecting the equine ovary, causing behavioral changes at rest and reduced performance. The reported success rate of ovariectomy in treating behavioral disorders is 64-86%. The aim of this study was to retrospectively evaluate the long-term follow-up of laparoscopic ovariectomy in mares in our case series, focusing on the owner's perspective of the behavior of the mares after surgery. In addition, the histopathological features of the removed ovaries were investigated. The clinical records of mares that underwent laparoscopic ovariectomy between 2015 and 2022 were retrospectively reviewed. Owners complaining of poor behavior were interviewed about the main behavioral problem leading to referral and its eventual resolution after surgery. Eleven mares were included. The most common complaints were increased sensitivity on both flanks (10/11, 91%) and general riding problems (9/11, 82%). In 5/11 cases (45%), both ovaries were removed by laparoscopic ovariectomy. Histopathologic findings consistent with GCT/GTCT were found in five out of six examined ovaries (five granulosa theca cell tumors, GTCT). According to owner interviews, the scores assigned to each behavior improved significantly after surgery, regardless of histological findings. Although many factors can influence the behavior of horses, granulosa cell tumors (GCTs) proved to be a common cause and, as reported by the owners, ovariectomy resulted in improvement or complete resolution of the abnormal behavior.

Analgesic and Sedative Effects of Epidural Lidocaine-Xylazine in Elective Bilateral Laparoscopic Ovariectomy in Standing Mule Mares

Simple Summary

Elective bilateral ovariectomy in mule mares is recommended to correct undesirable behaviour effects related to oestrus and also in order to improve work performance. This procedure is usually carried out in a standing position with a combination of sedative and analgesic drugs along with local anaesthesia of the ovarian pedicles. The aim of the study was to evaluate the effects of epidural lidocaine-xylazine in sedated standing mules undergoing elective bilateral laparoscopic ovariectomy. The findings suggest that no significant changes were found in heart rate, respiratory rate, rectal temperature with respect to baseline values. Sedation and analgesia were satisfactory in six out of the eight mules. Epidural analgesia with lidocaine-xylazine may be a good alternative to local anaesthetics infiltration of the ovarian pedicle for elective bilateral laparoscopic ovariectomy in standing mule mares, but further studies should be performed.

Abstract

The purpose of this study was to determine the analgesic efficacy and safety of epidural lidocaine-xylazine administration in standing mules undergoing elective bilateral laparoscopic ovariectomy in order to suppress unwanted behaviour. Eight mule mares were sedated with intramuscular 0.05 mg/kg acepromazine followed by 1.3 mg/kg of xylazine and 0.02 mg/kg of butorphanol intravenously. Sedation was maintained by a constant rate infusion of 0.6 mg/kg/h of xylazine. The paralumbar fossae were infiltrated with 30 mL of 2% lidocaine. Epidural anaesthesia was performed at the first intercoccygeal space with 0.2 mg/kg of lidocaine and 0.17 mg/kg of xylazine. After 15 min, bilateral laparoscopic ovariectomy was performed. Heart rate, respiratory rate, rectal temperature, invasive arterial blood pressure, degree of analgesia, sedation and ataxia were evaluated during surgery. The laparoscopic ovariectomy was successfully completed in all animals. Sedation and analgesia were considered satisfactory in six out of the eight mules. In conclusion, caudal epidural block allowed surgery to be easily completed in six out of eight. The animals did not show any signs of discomfort associated with nociception and were mostly calm during the procedures, however additional studies are needed to establish epidural doses of xylazine and lidocaine that result in reliable abdominal pain control in mules for standing ovariectomy.

Laparoscopic Ovariectomy in Standing Mule Mares

Mules are hybrids bred from the mating of a jack donkey and a horse mare, known for their strength and resistance and still used to work in agriculture. Although they have been for long considered sterile, evidence of estrus cycle has been demonstrated together with abnormal behavior related to ovarian activity. In this study, a bilateral standing laparoscopic ovariectomy technique using the LigaSure technology was applied in 10 mare mules for treating unwanted behavioral patterns. The technique was effectively performed on these animals avoiding the risk of general anesthesia, and the use of the LigaSure technology allowed good hemostasis and reduced surgical time. Owners declared to be satisfied with the resolution of the behavior.

Donkey and Mule Behavior

Donkeys and mules often are misunderstood because of their behavioral differences compared with horses. Working with these animals requires more patience and ability to notice the slightest changes in behavior to diagnose disease. Mules and donkeys form strong bonds and trust with familiar people and other equids. Training mules and hinnies from an early age is key to modifying behavior and acceptance of unfamiliar people. Reproductive behavior is different from that of horses and requires more patience when collecting jacks. Practitioners working with mules and donkeys should take a methodological approach and get to know the animal before performing examinations.