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Animal Nutrition

Scientific Papers

© Rory Harper

Maize green forage as a partial replacement for lettuce in the diet of West Indian manatee Trichechus manatus (Krajda et al., 2023)

October 2023

A study in JZAR described how the diet of a group of zoo-housed West Indian manatees was changed with the introduction of maize green forage as partial replacement for lettuce:
✔ Introduction of maize green forage increased concentration of dry matter and fibre in diet, while reducing crude protein.
✔ Due to reduced cost of maize green forage in comparison to lettuce, the zoo saved approximately €60,000 in three years.
✔ Maize green forage may be a suitable option for captive manatees, with potential health benefits and a reduction in feeding costs for the zoo.

Multi-criteria study on a change to a fruit-free diet in Cebidae and Cercopithecidae (Viallard et al., 2023)

October 2023

The effects of gradually removing fruit from the diets of five zoo-housed primate species (spider monkeys , Hamlyn  monkeys, L’Hoest  monkeys, Roloway  monkeys, and yellow-breasted capuchins) were monitored in a study published in JZAR:
✔ Lower sugar and higher fibre achieved with new diet.
✔ Hamlyn monkeys showed improved faeces consistency and spent more time feeding with new diet.
✔ Spider monkeys also showed an improvement in faeces consistency, while capuchins spent more time feeding.
✔ Further evidence of the potential benefits of fruit-free diets in zoo-housed primates.

Fasted and furious? Considerations on the use of fasting days in large carnivore husbandry (Kleinlugtenbelt et al., 2023)

July 2023

A study published in the JZAR surveyed the husbandry guidelines and feeding regimes of large carnivores in 44 European zoos:
✔ Husbandry guidelines did not state that fasting days should be preceded by gorge-feeding.
✔ Feeding regimes should be re-assessed to ensure large carnivores are gorge-fed (with satiety and gut extension) before fasting days.
✔ Feeding should be associated with high physical activity and cognitive challenges to better mimic natural feeding behaviours.

The behavioural effects of feeding lean meat vs whole rabbit carcasses to zoo jaguars Panthera onca (Enemark et al., 2023)

July 2023

How does the behaviour of zoo-housed jaguars differ when fed lean meat VS whole rabbit carcasses? A case study on three jaguars, published in Journal of Zoo & Aquarium Research, investigated: 
✔ Feeding-related behaviours increased by over 300% when fed whole carcasses - particularly in the first hour after food was presented.
✔ Despite this increase, difference accounted for less than 1% of daily time budget.
✔ Future studies can further investigate the impact of larger carcasses on the behaviour of this species in human care.

Nutritional effect of feeding enrichment using bamboo Pleioblastus spp. in zoo-kept Asian elephants Elephas maximus (Tsuchiya et al., 2023)

April 2023

Bamboo is often used as enrichment for zoo-housed herbivores, but does it have negative effects on nutrition? This was investigated in a study in the JZAR, focusing on four Asian elephants (4 - 8 years old):
✔ Diet with bamboo: portion of sudangrass hay replaced with bamboo (~20% of diet).
✔ No significant differences between diets in nutritional intake, digestibility or blood condition.
✔ Bamboo did not seem to affect the nutritional status of the elephants: applications to ex situ management.

Diet impacts the structure and function of the bacterial community in the gastrointestinal tract of a sloth bear
(Loudon et al., 2022)

October 2022

A research paper in the latest issue of Journal of Zoo Aquarium Research tested the effects of a new diet, lower in dietary starch, on the gastrointestinal tract of a zoo-housed sloth bear:
✔ Under new diet: bacterial community richness did not change BUT the relative abundance of some bacterial taxa did. 

✔ Evidence of increased protein digestion, amino acid fermentation and pH, and decreased acetate to propionate ratio found in faeces.
✔ Results suggest the need to better match the diets of captive sloth bears with their wild counterparts.

Effects of Storage Time and Thawing Method on Selected Nutrients in Whole Fish for Zoo Animal Nutrition
(Gimmel et al., 2022)

October 2022

Are the nutrients in whole fish affected by storage time and thawing method? A study in Animals looked into it:
Three thawing methods tested: refrigerator, room temperature, running water;
Vitamin B1 was below detection limits in most analysed samples of two of the fish species;
Significant decrease in Vitamins A, D3 and E after six-month storage;
More research recommended on the effects of thawing method;
Recommendations for zoo animal nutrition: vitamins B1 and E supplementation, and avoid storing fish for more than six months.

Dietary protein requirement for captive juvenile green turtles (Chelonia mydas(Jualaong et al., 2022)

June 2022

The protein requirements of juvenile green turtles, part of a head-starting programme, were investigated in a study in Zoo Biology:

45 turtles put in different tanks, in groups of 3, and fed diets with different protein %;
Highest growth performance & feed utilisation in turtles on diet with 40% protein;
Calcium deposition & phosphorus also improved under this diet, supporting healthy bones & hard carapace;
Estimated optimal protein level: 40.6%.

Feeding regimen and growth comparison in two related African painted dog Lycaon pictus litters (Cloutier et al., 2022)

April 2022

A study in Journal of Zoo & Aquarium Research compared growth in two related captive African painted dog litters under different feeding regimes:
One litter was fed freely while the other was fed at regular intervals;
Growth differences in: hind leg/body length ratios, front and hind leg/body length differentials, and mean body mass; 
No differences in body length, ear height, head circumference, and muzzle length.
Small sample size but interesting findings that call for further research on the topic.

Keeping the golden mantella golden: The effect of dietary carotenoid supplementation and UV provision on the colouration and growth of Mantella aurantiaca
(Newtons-Youens, Michaels & Preziosi, 2022)

April 2022

How to maintain the bright colouration of golden mantellas in captivity? A new study in Journal of Zoo & Aquarium Research investigated whether carotenoid supplementation & UV provision had an effect on it:

✔ An enhanced carotenoid diet and UVB light provision both increased colouration - more so when provided separately than in combination;
✔ Frogsi in a "red diet" showed a more intense red colouration than those in a "yellow diet" (same carotenoid concentration, but different profile).
✔ Both concentration and profile of carotenoids influence colouration of golden mantellas.

Assessment of Feeding Behavior of the Zoo-Housed Lesser Anteater (Tamandua tetradactyla) and Nutritional Values of Natural Prey (Zárate et al., 2021)

January 2022

A paper in JZBG looked into the behaviour of zoo-housed lesser anteaters when fed live ants & termites:

 Anteaters consumed more termites & spent more time feeding on them than ants;

 Ant meal = higher protein and lipids;

 Termite meal = higher carbohydrate digestibility;

 Insect consumption may be associated with nutritional and digestibility values.

New insights into dietary management of polar bears (Ursus maritimus) and brown bears (U. arctos(Robbins et al., 2021)

November 2021

New paper in Zoo Biology looked into the diets of polar bears & brown bears:

Both wild & captive bears select diets with low protein and higher fat or digestible carbohydrate concentration;

Captive bears are often fed high-protein diets, which may be associated with their susceptibility to renal failure & liver cancer;

Diets of captive polar & brown bears should be reviewed to better match their preferred macronutrients ratios.

Colony composition and nutrient analysis of Polyrhachis dives ants, a natural prey of the Chinese pangolin (Manis pentadactyla(Xu et al., 2021)

October 2021

A study in Zoo Biology analysed the nutritional contents & composition of a colony of Polyrhachis dives ants - key prey in the diet of the critically endangered Chinese pangolin:

Colony consisted mostly of adults, but also pupae, larvae & eggs;

High protein & chitin, low fat & formic acid identified in both colony & adult ants;

Colony & adult ants differed in several aspects of chemical composition - diet of captive pangolins shouldn't be composed solely by adult ants as they prey on all colony in the wild;

Applications to husbandry and nutrition of captive Chinese pangolins.

Investigating food preference in zoo-housed meerkats 
(Brox et al., 2021)

July 2021

A study in Zoo Biology looked into food preferences in zoo-housed meerkats:

Clear, stable preference hierarchy identified;

High in preference hierarchy: Cooked eggs & raw meat;

Lower in preference hierarchy: Vegetables;

Slight differences between juveniles & adults;

Applications to zoo management and welfare assessments.

A modified diet to support conservation of the Atala hairstreak butterfly (Eumaeus atala Poey)(Braatz et al., 2021)

June 2021

A study in Zoo Biology investigated the suitability of a freeze-dried diet in a captive breeding programme for the Atala hairstreak butterfly:

Smaller larvae fed freeze-dried leaves & stems from host plant;

Larger larvae switched to live-plant diet;

Highly successful method: over 3400 individuals released into the wild;

Freeze-dried diet is appropriate substitute when live plant is scarce or not available - potential applications to other butterfly species.

Ensiling of maple leaves and its use in winter nutrition of mantled guereza (Colobus guereza) (Lasek et al., 2021)

May 2021

A paper in Zoo Biology evaluated the composition and nutritional value of maple leaf silage and its suitability for inclusion in the winter diets of captive mantled guerezas:

Most nutrients were unaffected by ensiling process;

Mantled guerezas promptly fed on maple leaf silage.

Higher nutrient intake when maple leaf silage included in diet;

Ensiling, with or without additives, effectively conserved maple leaves.

Grading fecal consistency in an omnivorous carnivore, the brown bear: Abandoning the concept of uniform feces (De Cuyper et al., 2021)

February 2021

A study in Zoo Biology graded faecal consistency in nine zoo-housed brown bears fed a variety of diets:

Six-point scale established for uniform faeces;

Additional grading system for faeces with dual consistencies (observed in 11% of all faeces);

More vegetation or whole prey seemed to be associated with firmer faeces;

Faecal consistency is affected by diet in this species and can be used for gut health monitoring.

Circulating nutrients and hematological parameters in managed African elephants (Loxodonta Africana) over a 1‐year period (Wood et al., 2020)

July 2020

A study published in Zoo Biology investigated the circulating nutrients and hematological parameters in zoo-housed African elephants, over a one-year period:

Seasonal changes in circulating nutrients;

African elephants fed mixed feedstuff & fortified pellet diets may not need Vitamin E supplementation.

Assessment of circulating nutrients provides evidence for better elephant management in captivity.

Daily lettuce supplements promote foraging behavior and modify the gut microbiota in captive frugivores (Greene et al., 2020).

July 2020

A study in Zoo Biology investigated the effects of daily lettuce supplements on the behaviour and gut microbiota of captive ruffed lemurs:

The lemurs (especially younger individuals) consistently foraged on the lettuce during the study period;

Enrichment of potentially-beneficial microbes in the guts;

Lettuce provision is potentially beneficial to captive frugivores.

Dietary management of hypercholesterolemia in a bachelor group of zoo-housed Slender-tailed meerkats (Suricata suricatta) (Dobbs et al., 2020)

October 2020

Captive meerkats are prone to high cholesterol levels, which can lead to health problems. A study in JZAR investigated the impact of a new diet on cholesterol levels in a group of zoo-housed meerkats:

New diet with lower saturated fat & cholesterol implemented;

Reduction of cholesterol levels in all individual meerkats;

Good body condition score & weight reported after new diet introduction.


Photo credit: Twycross Zoo

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