donkey

The female donkey is often known as a mare or jenny, the male as a donkey stallion or jack.

Reproductive behaviours

Sexual behaviour is often more exaggerated in the donkey and stallion-like behaviour may persist in the male donkey after castration. It is recommended that, unless being used for breeding, all male donkeys are castrated between 6 and 18 months of age.

Females will start cycling regularly between 10 and 22 months old with a wide variation in oestrus duration of 2–10 days. Seasonality of ovarian activity is variable and likely to be influenced by photoperiod, nutrition and temperature. Older females will tend to show longer interovulatory intervals. Signs of oestrus observed in females include mounting (females will mount each other with the oestrous female on the bottom), mouth clapping, winking (eversion of the clitoris), raising the tail, urinating, posturing (abducted hindlegs, arched tail) and backing up towards the jack. During dioestrus, females will show a lack of interest in the male and will move away or kick if male interest is persistent.

Puberty in the male donkey occurs between 16 and 20 months, with sexual maturity at around 3 years of age; however, males may show mounting behaviours from young foals. Male sexual behaviour differs from horses in that jacks are often slow to achieve erection (10–40 min) [1] and may mount a jenny several times before becoming fully erect. Several periods of sexual interaction are usual, separated by periods where the jack will withdraw away from the jenny. Donkey stallions are territorial and can become very aggressive, especially in the presence of competing males and females in season.

Reproductive anatomy

Donkey reproductive organs are proportionally larger than horse reproductive organs and ligation of the testicular artery is mandatory when castrating donkey stallions [2]. Even slim donkeys can have large amounts of scrotal fat so care should be taken post castration that fat does not prolapse from the surgical site. Castration via the inguinal approach is recommended for large or mature male donkeys over 4 years of age. Donkeys castrated after 18 months of age are more likely to retain stallion-like behaviours.

Testing for anti-Müllerian hormone (AMH) has welfare and practical advantages over the hCG stimulation test for diagnosing cryptorchid donkeys. It only requires a single blood sample and following castration, AMH concentrations are undetectable within approximately 2 days, making AMH a useful test if there is any doubt over the success of a recent castration [3].

The jenny’s reproductive organ anatomy is generally similar to that of the horse mare although due to size, rectal examination of miniature donkeys may be challenging. AI techniques are similar to those described in the horse although the anatomy of the cervix, coning towards the caudal end [4], may make manipulation of the cervix for uterine flushing or other techniques requiring access to the uterine cavity during dioestrus difficult.

Pregnancy

Owner education is essential as many donkey owners are often inexperienced, unprepared or unaware that their donkey is in foal. Gestation is longer and has greater variability than horses and ponies; ranging from 11 to 14.5 months. The incidence of twin foaling at full gestation is reportedly higher than in horses and ponies.

Pregnancy diagnosis can include transrectal ultrasound; optimal time for early diagnosis is 14 days post ovulation, transrectal palpation from day 40 [2] and oestrone sulfate testing from day 120.

Pregnant females should be vaccinated following recommended equine guidelines, and prior to foaling, parasite prevention should be put into place including appropriate pasture management during and after pregnancy. Body condition should be regularly assessed and feed adjusted appropriately. Pregnancy and lactation are risk factors for hyperlipaemia.

Electrolyte levels in the mammary secretions can be used to predict foaling. A sodium:potassium ratio of <1 is indicative of foaling occurring in the next 24–48 h [2]. Calcium levels are less reliable but can also be used.

Jennies have a higher tendency to exhibit foal heat than horses and ponies, with higher pregnancy rates [2].

Foal management

The incidence of failure of passive transfer ranges from 3 to 40% [5]. Risk factors are similar to those found in the horse and the IgG level considered normal in horse foals is used. There is a problem with recognition of prematurity or dysmaturity when compared with horses. In horses, the covering date is usually known and the gestation period is more defined. In donkeys, especially in miniatures, the variation in gestation length can make it very hard to define a premature donkey foal [4]. Despite their thick fluffy coat (appearance of warmth and hardiness compared to the horse foal), donkey foals are not very hardy and require warmth and suitable shelter [5].

References

1. S. Purdy. (2019) Small herd behaviour in domestic donkeys. Equine Veterinary Education 31, 199-202.
2. The Donkey Sanctuary. (2018) The Reproductive System. In: The Clinical Companion of the Donkey, 1st edition, Matador, Leicestershire, pp 73-86.
3. N. Matthews, T. Taylor, V. E. N. Blanchard South, A. E. Durham. (2017) Use of Anti-Müllerian hormone (AMH) for the diagnosis of cryptorchidism in donkeys. ECEIM Congress 2016 Abstracts. Journal of Veterinary International Medicine 31, 604-618.
4. N. Matthews, T. Taylor, T. Blanchard. (2003) An overview of reproduction in donkeys. International Animal Health News: A publication of Christian Veterinary Mission 18.
5. N. Aronoff. (2010) The donkey neonate. In: Veterinary Care of Donkeys, Editors: N. Matthews, T. Taylor, International Veterinary Information Service, Ithaca NY. Last updated: 29 March 2010.

Cyathostomins, the predominant parasitic nematodes of equids, have developed varying degrees of resistance to all three classes of anthelmintic licensed for use in horses. It is essential that the effectiveness of alternative methods of control for these pathogens are quantified, including incorporating climatic data and the commonly advocated practice of removal of faeces from pasture. Here, we obtained monthly faecal worm egg counts (FWEC, n=4,460 individual counts) from 803 donkeys based at The Donkey Sanctuary (Devon, UK). The dataset also included age, sex, field, FWEC history and previous anthelmintic administrations in each individual, as well as the pasture hygiene management method applied in the field where the donkey was grazed. FWEC were analysed alongside local climatic data using a generalised linear mixed model to assess associations between these variables and each observed monthly FWEC. The preferred model was identified using a model selection algorithm based on penalised likelihoods, and associated a 2.1% decrease in FWEC per day with air frost two calendar months ago (p<0.001) and a 38% lower FWEC in groups with twice weekly manual faecal removal compared to those with no faecal removal (p=0.004). Other weather effects, both alone and as interaction terms with the average FWEC of the field were included in the model, alongside individual FWEC history with anthelmintic administration as interaction terms and date as a single term. Our study identifies factors that may be useful as part of on-going predictive modelling based methods of improving targeted selective therapy.

Nutritional status, measured as body condition, has been used to assess welfare in working equines. Dental abnormalities have a substantial impact on the nutritional status of equines because they limit digestibility of foods and then nutrient utilisation. In Mexico, most of the working equines show body condition scores below 2.5 throughout the year and teeth problems may have a role in this. The purpose of this work was to investigate the prevalence of dental disorders in a population of working equines in Mexico. The study was run within with the work of the mobile clinics of DS-ILPH-UNAM programme. A total of 3,838 equines in 47 rural villages were assessed. Data were collected by surveys and by recording dental disorders in a complete oral examination. Species (donkey, horse or mule), sex (male or female), age and body condition score of every animal was recorded. The prevalence of animals with dental disorders and the frequency of each dental pathology in the affected animals were calculated. Body condition and age of affected animals were recorded. The average prevalence of serious dental disorder was low in all the cases (13%) and did not differ among species and sexes. The most frequent condition affecting incisor line of occlusion was ventral curvature. Enamel points, hooks, ramps, accentuated transverse ridges and steps were the most frequent abnormalities of cheek teeth rows. The average age of affected animals was 10.4±5.8 years, ranging from two to 40 years. Age did not differ among species or sexes. Mules showed higher average age, but the range was narrower than in other species. With regards to the body condition, more than 60% of the affected equines were in the lowest range (<2.5). These results are the first to describe the prevalence of serious dental abnormalities in working equines in Mexico and suggest the subject deserves further investigation. The data would allow strategies aimed at improving equine welfare via nutritional status.

The Donkey Sanctuary is a British charitable organisation based in Sidmouth, Devon, England, which’s mission is to transform the quality of life for donkeys, mules and people worldwide through greater understanding, collaboration and support, and by promoting lasting, mutually life-enhancing relationships. The Donkey Sanctuary was founded in 1969 and registered as a charity in 1973 by Dr Elisabeth Svendsen. The Donkey Sanctuary has a total of seven farms in the UK including a reception farm for new arrivals where the study is based, a laboratory, pathologist and an specialized hospital. The Donkey Sanctuary currently looks after around 2.600 animals (in a total estimated UK census of 10.000 animals).

Animals are admitted into a quarantine Farm where they spend a minimun of 6 weeks to assess their health status including full coprological study. Donkey are relinquished or rescued by the charity and arrive from different origins: directly from a private owner, another organitation or hospital or one of the charity’s holding base located in different parts of the country. This animals wopuld have been previosly admitted into those centres and taken there due to biosecirity reasons or becuase transport could be in detriment of their health at that time. Animals that need urgent veterinary treatment would be sent to the closest equine hospital for treatment until consider fit to be transported.

Management of hundreds of animals and their pasture can be challenging from the parasitological point of view, especially if we tend into consideration that the majority of donkeys unlike horses would be asyntomathic despite having high parasite burdens. It is rare for donkeys to show signs such as diaorrhea, weight loss or a poor body condition that are more commonly found in the horse.