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Animal Health & Physiology

Scientific Papers

© Rory Harper

Venous blood gas and lactate values in adult giraffe trained for voluntary jugular phlebotomy (Cole et al., 2024

april 2024

A paper in Zoo Biology described the use of a point-of-care blood gas and lactate analyser to take blood from the veins (venepuncture/phlebotomy) of 20 trained giraffes, without anaesthesia or physical restraint:
Reference values for venous blood gas and lactate concentrations were established.
Blood gas values differed across giraffes at different altitudes.
Quick and accurate assessments of giraffe physiological indicators can be obtained with a point-of-care blood gas analyser.
This method, with voluntary training programmes, can facilitate medical care, husbandry and welfare of captive giraffes.

Weight as an indicator of enclosure suitability in Livingstone's fruit bats (Pteropus livingstonii) (Price et al., 2024

March 2024

The weights of zoo-housed and wild-caught Livingstone's fruit bats were compared in a paper published in Zoo Biology:
Wild males heavier and have longer forearms than females.
Zoo-housed bats heavier than wild counterparts, particularly those housed in enclosures that restrict flight.
Females are particularly vulnerable to weight gain when housed in enclosures that restrict flight, as they get heavier than males under those conditions.
Aviary-style enclosures that enable flight reduce weight gain in captive fruit bats - applications to ex situ management of species.

Abnormal swimming is associated with inner ear damage and improves with meclizine treatment and increased habitat complexity: A case study in Urobatis jamaicensis (Puishys et al., 2024

January 2024

A case study published in the new issue of Journal of Zoo Aquarium Research investigated infection-related abnormal swimming in an aquarium-housed yellow stingray:
An inner ear infection was thought to be causing the abnormal swimming behaviour.
A meclizine treatment resulted in reduction of abnormal swimming, and increased normal swimming and resting.

Further reduction in abnormal behaviours after the stingray returned to its more complex home habitat, from the isolated treatment tank.

Body Shape Analysis in Reticulated Giraffe, Okapi, and Black Rhinoceros Using Three-Dimensional Laser Measurements (Kido et al., 2024

January 2024

A study in JZBG tested the use of three-dimensional laser measurements to determine body shape of giraffes, okapis and black rhinoceroses:
Cross-sectional area, width, and height in transverse section were determined for all individuals.

Changes in body shape revealed by relative change rates of each variable in relation to measurements..
Three-dimensional laser measurements accurate method to determine body shape, removing issues with inter-observer variability.
May be an appropriate solution for institutions that lack the scales to weigh megafauna.

Zoos as Sentinels? A Meta-Analysis of Seroprevalence of Terrestrial Mammalian Viruses in Zoos (Van Leeuwen et al., 2023

May 2023

According to a new review in EcoHealth that looked into the prevalence of pathogens (seroprevalence) across mammalian zoo populations:
By housing wild animals, zoos have privileged opportunities to detect, identify and monitor animal-related pathogens.
Higher prevalence of viruses targeting specific host taxa and those transmitted by direct contact.
Recommendations: more research needed on a wider range of taxa, and on free-living and domestic animals within zoo areas, as well as an increase in public availability of data.
Zoos can be sentinels for disease monitoring, which further highlights their contributions to the OneHealth framework (linking human, animal and environmental health).

Effect of four eggshell repair materials on weight loss during incubation of white leghorn chicken eggs (Byrne et al., 2023

October 2023

A study published in Zoo Biology tested the effects of several eggshell repair materials (nail polish, synthetic glue, medical dressing, and molten wax film) on weight loss during incubation of leghorn chicken eggs:
Coverings of up to 35% of the eggshell surface had no effect on weight loss.
The position of the patch had no effect on weight loss, and there were no differences between repair materials.
Small repairs on cracked eggs did not seem to have harmful effects.

The Effects of Photobiomodulation Therapy on the Healing of Eastern Box Turtle (Terrapene carolina) Shells (Souza, Masterson & Harrison, 2023

August 2023

A study in JZBG tested whether photobiomodulation therapy (cold laser or low-level laser therapy) affected healing of shell fractures in Eastern box turtles:

20 turtles in rehabilitation: all received similar medical treatments, except the "photobiomodulation group" also received the laser treatment.

Shell density did not significantly differ between photobiomodulation and control groups.

Width of shell fractures significantly decreased after laser treatment.

Further research recommended but photobiomodulation may be an effective way to promote healing in turtle shell fractures.

UV irradiance effects on Komodo dragon (Varanus komodoensis) vitamin D3, egg production, and behavior: A case study (Wood et al., 2023) 

August 2023

Paper in Zoo Biology: the behaviour and physiology of two zoo-housed Komodo dragons were studied before and after they were housed in an outdoor area and in an indoor area with redesigned lighting:
Female: when moved outdoors, 98% increase in Vitamin D3 levels; laid first clutch of eggs.
Male: when moved indoors, vitamin D3 levels remained consistent for 200 days; higher activity in high UV irradiance.
UV lamps stopped producing the appropriate UV irradiance within 3.5 months - UV monitoring of indoor habitats recommended. 

Utilising routine non-invasive faecal samples for the detection of oestrus and early gestation in okapi (Okapi johnstoni(O'Hanlon et al., 2023) 

July 2023

A new paper in Theriogenology Wild discussed how to monitor the oestrus cycle of captive okapis with routine non-invasive faecal sampling:
Oestrous cycles & gestations of four females (seven pregnancies) were monitored.
Oestrogen peaked at beginning of inter-luteal phase, when progestagen decreasing.
Confirmation of gestation within first trimester, when progestagen remained at luteal phase concentrations for at least 20 days
Okapi has similar oestrous cycles to other giraffids
Applications to ex situ reproductive management of okapis. 

The first report of the clinical diagnosis and surgical management of pyometra in two cheetahs (Acinonyx jubatus(Gazendam et al., 2023) 

July 2023

The first report of clinical diagnosis and surgical management of pyometra (i.e. uterine infection) in two captive cheetahs has been published in Theriogenology Wild:
Transabdominal ultrasonography facilitated diagnosis.
Diagnosis confirmed by retrospective endocrinological, cytological and bacteriological testing.
Description provided for the successful induction, anaesthetic protocol, and surgical method for ovariohysterectomy.
Applications to the in situ and ex situ health management of cheetahs & other carnivores.

A new approach to the vasectomy of African lions (Panthera leo(Gazendam et al., 2023) 

June 2023

Four adult African lions were submitted to a vasectomy, using a new approach that is described in a paper in the Journal of South African Veterinary Association:
Ductus deferens located bilaterally, dissected and transected.
Fascial interposition was used to decrease the chances of recanalisation⤵️
Method used in human medicine -  prostatic end of ductus fixated outside tunica vaginalis; testicular end remained within tunic.
Twelve months later: no issues reported, no litters produced.
Applications to reproductive management of captive lions.

Diagnosing gastric ulcers in bottlenose dolphins (Tursiops sp.) using gastroscopy and cytology (Buhrmann, Gridley & Oellermann, 2023) 

April 2023

Gastric ulcers have been documented in wild and captive bottlenose dolphins, and a paper in Zoo Biology explored the use of gastroscopy and cytology to diagnose them:
Data on gastric ulcer severity collected by endoscopy compared with cytological data of gastric fluid.
Cytological data was not linked with ulcer severity.
Collection of cytological data is less intensive than gastroscopy, but it is NOT a viable alternative for gastric ulcer diagnosis.

Fecal microbiota transplants modulate the gut microbiome of a two-toed sloth (Choloepus didactylus(Thacher et al., 202). 

January 2023

A new study in Zoo Biology described the effects of fecal microbiota transplants on the microbiome of a two-toed sloth exhibiting abnormal bowel movements:
Microbiome showed positive changes in diversity, composition and membership (more closely resembling the healthy donor's).
Pronounced improvement in the bowel movements, although it was temporary.
Fecal microbiota transplants can help improving gut microbiome & health.

Training a Giraffe (Giraffa camelopardalis reticulata) for Voluntary Foot Radiographs at Dubai Safari Park 
(Booth et al., 2022). 

December 2022

A zoo-housed giraffe was trained for voluntary foot radiographs when she started displaying signs of lameness, with the training process described in a paper in the Journal of Zoological and Botanical Gardens:
Procedure: Positive reinforcement in a protected contact set up.
Giraffe was taught six behaviours: (1) Target Training, (2) Recall, (3) Back Up, (4) Station, (5) Lift Foot, (6) Front Foot Radiograph.
Radiographs achieved used for clinical evaluation.
Training for medical procedures is an effective method to reduce stress & other risks associated.

Single or repeated immunization against GnRH fails to completely abolish spermatogenesis in dwarf bucks (Capra hircus(Giriboni et al., 2022). 

October 2022

A study in Zoo Biology looked into contraception of dwarf bucks via immunisation against gonadotropin-releasing hormone (GnRH):
Comparison of single immunisation of Improvac (two doses) VS repeated immunisation (one dose every six months); 
Males in repeated immunisation group: greater decrease in scrotal circumference, testosterone, male odor & sperm quality.
Repeated Improvac treatment reduced BUT did not completely block fertility. 
Applications to ex situ contraception & population management.

Current surveillance practices for shedding of elephant endotheliotropic herpesviruses in breeding and bachelor Asian elephant Elephas maximus herds in Europe (Perrin et al., 2022). 

October 2022

A paper in Journal of Zoo Aquarium Research investigated current practices in surveilling endotheliotropic herpesvirus shedding in European herds of captive Asian elephants:
42% of breeding institutions had protocols for EEHV screening;
30% monitored viral shedding;
Shedding data (2,863 samples from 12 institutions): 13.9% of samples & 48.9% of elephants tested positive for EEHV;
Evidence of EEHV present in all 12 herds;
Routine monitoring of EEHV is recommended.

Vitamin D status in chimpanzees in human care: a Europe wide study (Moittié et al., 2022). 

October 2022

A new paper in Scientific Reports has looked into the vitamin D status of chimpanzees in human care:
245 samples from chimpanzees housed at 32 European zoos.
Inadequate vitamin D levels detected in 33.1% of samples.
Season of the year, health status & daily outdoor access had significant effect on vitamin D status.
These inadequate levels can lead to several diseases.
Husbandry & nutrition practices for this species must be reviewed & adjusted.

Translocation of European captive pink pigeons Nesoenas mayeri to Mauritius: disease risk analysis for production of a pre-export quarantine protocol (Shopland et al., 2022). 

October 2022

The new issue of Journal of Zoo & Aquarium Research is out, featuring the Mauritian pink pigeon on the cover... This species is also featured in one of the papers, with a disease risk analysis of a translocation of pigeons from the European ex situ programme (EEP) to the captive breeding colony in Mauritius, to increase the genetic diversity there:
21 pathogens were medium or high risk to the pink pigeon population.
Some were also a risk to poultry & endemic birds.
Pre-export quarantine protocol & mitigation techniques developed to reduce risk.
On top of 30-day quarantine, multiple testing recommended (e.g. blood samples, radiography, faecal sampling, cloacal swabbing, etc.).
Protocol also has applications to future translocations.

Predictors of testosterone in zoo-managed male African elephants (Loxodonta Africana(Campbell, Wilson & Morfeld, 2022). 

September 2022

A paper in Zoo Biology investigated what factors influence fertility (i.e. testosterone production) in zoo-housed African elephant bulls:
Physiology: Glucose-to-insulin ratio (+) associated with testosterone;
Physical: Musth score & moderate exercise (+) associated with testosterone (which was lower in overweight elephants);
Social: Social contact & female interactions increased testosterone;
Management: Time spent outdoors & browse opportunities increased testosterone.

Age and growth of the zebra shark Stegostoma tigrinum (Forster 1781), at Loro Parque Aquarium (Toledo Padilla et al., 2022). 

July 2022

A study in JZAR looked into age and growth of zoo-housed zebra sharks:
  288 biometric measurements from 24 individuals;
  Average length & weight at birth were 26.5 cm & 71.94 g, respectively;
  Accelerated growth in first 3.5 years of life;
  No differences in growth between males & females;
  Strong correlation between length & weight.

Mortality and morbidity in captive Livingstone’s fruit bats Pteropus livingstonii (Segura-Cortijos et al., 2022). 

July 2022

A study in Journal of Zoo Aquarium Research reviewed medical records of 161 Livingstone's bats housed at two zoos between 1992 and 2017:
 Most common causes of morbidity: wounds, localised inflammation & fractures;
 Males & immature individuals more likely to suffer wounds;
 Females more likely to suffer fractures;
 Most common causes of mortality: early foetal death, heart diseases & conspecific aggression.

Body mass and growth rates in captive chimpanzees (Pan troglodytes) cared for in African wildlife sanctuaries, zoological institutions, and research facilities (Curry et al., 2022). 

July 2022

A study in Zoo Biology compared body mass & growth rates of chimpanzees housed at zoos, sanctuaries & research facilities:
 Higher body mass in adult zoo & research chimps;
 Slower growth rates in sanctuary chimps;
 Older age at maturation (body mass) for sanctuary chimps;
 Growth patterns of chimps differ between captive environments.

American alligator (Alligator mississippiensis) weight gain in captivity and implications for captive reptile body condition
(Kruis et al., 2022). 

July 2022

A paper in Zoo Biology compared body condition in captive and wild American alligators:
209 captive & 935 wild alligators;
Higher body condition in adult captive alligators (weight gain in males);
No differences found between juvenile captive & wild individuals;
Movement & diet likely played a role in differences detected in adult individuals.

Behavioural evaluation of a meerkat Suricata suricatta group after insertion of deslorelin contraceptive implant in the dominant female (Colbachini et al., 2022). 

January 2022

A study in Journal of Zoo & Aquarium Research looked into the behaviour of a zoo-housed meerkat group after the dominant female was implanted with a deslorelin contraceptive:
✔  No births - effective reproductive control;
✔  Social hierarchy and relationships remained stable;
✔  Agonistic behaviours decreased;
✔  12 months later: follicles detected in ovaries - return to reproductive activity?  
✔  Further research on long-term effects recommended.

Morphological appearance and effects of castration on blackback gorillas Gorilla gorilla gorilla in the EAZA ex-situ population (Torres, Poveda & Teijeiro, 2022)

January 2022

Does castration affect the development and appearance of captive blackback gorillas? A study in Journal of Zoo & Aquarium Research found:
✔ No significant differences in morphological measures between castrated & intact males;
✔ Lower average weight in castrated males than intact ones, & similar to females;
✔ Lack of sagittal ridge development & secondary sexual traits in castrated males.

Cancer risk across mammals (Vincze et al., 2021)

December 2021

A paper in Nature investigated cancer risk across mammalian taxa, using data from zoo-housed mammals (110,148 individuals, 191 species):

Carnivorous mammals have highest cancer-related mortality (especially mammal-consuming ones);

Cancer mortality risk is independent of body mass & adult life expectancy;

Important findings to help the understanding of the evolution of cancer resistance while highlighting the importance of data generated from zoo animals.

Incidence of pregnancy loss and characterization of fetal development in red pandas (Lowe & Curry, 2021)

November 2021

A paper in Reproduction & Fertility looked into pregnancy loss & fetal development in zoo-housed red pandas:

Trans-abdominal ultrasound examinations onfemales over 10-year period - 12 profiles;

Pregnancy identified in 10 profiles, with 40% of those showing fetal loss;

Pregnancy loss (no cubs produced) in 20% of cases, partial loss (one cub lost, one born) in other 20% of cases.

Fetal loss between days 51 & 23 pre-partum;

Fetal growth characteristics reported - applications to breeding management of this species in captivity.

Luteal phase length, endometrial edema, and behavior differentiate post-ovulatory events in a giant panda (Ailuropoda melanoleuca) (Magnus et al., 2021)

October 2021

A paper in Zoo Biology compared post-ovulatory characteristics in a giant panda during a pseudopregnancy (2014) and a pregnancy (2015) at Toronto Zoo:
Pseudopregnancy: minimal pre-partum behaviours, unusual uterine edemas & folding, extended luteal phase;
Pregnancy: increased feeding time with rise in primary progestagen, followed by a decrease in appetite and activity, and pre-partum behaviours (changes started 25 days before birth);
Monitoring behaviour, morphology & urinary-endocrine profiles may facilitate distrinction between pregnancies & pseudopregnancies in giant pandas.

Assessing the effects of biosecurity measures in terrarium managements (Jensen, Jensen & Bertelsen, 2021)

July 2021

A paper in JZAR described the effectiveness of biosecurity measures (gloves, designated tools or a combination of both) in reducing pathogen transfer in terrarium management:
Combination of tools & gloves significantly reduced contamination;
The use of gloves or tools alone did not significantly decrease contamination;
The combined use of simple biosecurity measures can drastically reduce risk of pathogen transfer in reptile & amphibian captive populations.

Reproductive suppression of giraffe (Giraffa camelopardalis) under managed care using a GnRH immunological products (Moresco et al., 2021)

September 2021

Paper in Zoo Biology discussed the applications of Improvest® (GnRH immunological product) in suppressing reproduction in seven captive female giraffes:

Ovarian activity stopped in all treated females, reducing male interest & pursuit of females;

Supplemental contraception did not reduce effectiveness of Improvest®;

Reversible: Treatment stopped 1.5 years later & ovarian activity resumed 90 days after that;

Small sample size but interesting applications to captive management of giraffes.

Development of an image-based body condition score for giraffes Giraffa camelopardalis and a comparison of zoo-housed and free-ranging individuals (Clavadetscher et al., 2021)

August 2021

An image-based Body Condition Score (BCS) has been developed for giraffes and published in JZAR:
BCS developed for both shoulder & hip areas (rib area not useful for BCS);
Score applied & validated in both free-ranging & zoo-housed giraffes;
Low scores should be avoided in zoo-housed giraffes but no evidence that high scores are detrimental;
On average, higher scores in zoo-housed animals improvements in zoo diets & less restrictions than in the wild.

Sex‐specific actuarial and reproductive senescence in zoo‐housed tiger (Panthera tigris): The importance of sub‐species for conservation (Tidière et al., 2021)

April 2021

A study in Zoo Biology looked into data from the International Tiger Studbook to investigate reproductive parameters and survival in the captive tiger population:

Low adult mortality & progressive increase of mortality rates after 10 years of age (longevity: 19 years).

Females: highest reproductive parameters (litter size and cub survival) when 7-9 years old;

Differences found between sub-species, highlighting the importance of considering them separately.

Adiposity, reproductive and metabolic health, and activity levels in zoo Asian elephant (Elephas maximus) (Chusyd et al., 2021)

January 2021

New research looked into body fat, metabolism and activity levels of Asian elephants in nine North American zoos:

Higher body fat not associated with abnormal reproductive cycles;

Walking rates similar to those of wild individuals;

Higher insulin levels in individuals with higher body fat;

Threshold for "obesity" in this species was attempted but further research required;

Obesity may not be such a problem in this species but may cause metabolic perturbations.


Photo credit: Smithsonian's National Zoo

Quantification and risk factor analysis of elephant endotheliotropic herpesvirus-haemorrhagic disease fatalities in Asian elephants (Elephas maximus) in Europe (1985-2017) (Perrin et al., 2021)

January 2021

The endotheliotropic herpesvirus-haemorrhagic disease (EEHV-HD) is a major cause of death in captive Asian elephants and increasingly recognised in their wild counterparts as well. A risk factor analysis of this disease in Europe (1985-2017) found the following:

EEHV-HD accounted for 57% of Asian elephant deaths;

Median age of EEHV-HD deaths: 2.6 years;

Similar risk for ;

Only significant risk factor identified was a previous EEHV-HD death in the institution;

Exposure to new elephants was not a significant risk factor.


Photo credit: Copenhagen Zoo

Monitoring great ape heart health through innovative electrocardiogram technology: Training methodologies and welfare implications (Cloutier Barbour et al., 2020)

September 2020

Heart disease is a major cause of mortality in zoo-housed great apes. A study in Zoo Biology introduced a electrocardiogram technology that facilitates the monitoring of great ape heart health:
Kardiamobile allows for voluntary, instant, reliable & economic electrocardiogram readings;
Operant conditioning training guidelines provided;
System generates evidence to inform management regarding great ape heart health.

A Retrospective Study of Macropod Progressive Periodontal Disease (“Lumpy Jaw”) in Captive Macropods across Australia and Europe: Using Data from the Past to Inform Future Macropod Management (Rendle et al., 2020)

October 2020

New research looked into "lumpy jaw" disease in captive macropods:
High mortality (62.5% for Australian & European institutions);
Risk of developing the disease increased with age;
Different incidence rates & risk of infection between institutions and geographic regions;
Recommendations to reduce disease risk were provided.


Photo credit: Perth Zoo

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