Research Article, J Vet Sci Med Diagn Vol: 13 Issue: 5

Significance of Branches and Leaves as Feed Components for Captive Western Lowland Gorillas

Misako Namiki^1* and Toyokazu Kobayashi²

¹Department of Animal Sciences, Teikyo University of Science, Tokyo West Campus, Yatsusawa, Uenohara City, Japan

²Department of Animal Sciences, Teikyo University of Science, Senju Campus, Tokyo, Japan

*Corresponding Author: Misako Namiki,
Department of Animal Sciences, Teikyo University of Science, Tokyo West Campus, Uenohara City, Japan
E-mail: misakonamiki@ntu.ac.jp

Received date: 02 September, 2024, Manuscript No. Jvsmd-24-147095;

Editor assigned date: 04 September, 2024, PreQC No. Jvsmd-24-147095 (PQ);

Reviewed date: 18 September, 2024, QC No. Jvsmd-24-147095;

Revised date: 25 September, 2024, Manuscript No. Jvsmd-24-147095 (R);

Published date: 02 October, 2024, DOI: 10.4172/2324-83414.1000109

Citation: Namiki M, Kobayashi T (2024) Significance of Branches and Leaves as Feed Components for Captive Western Lowland Gorillas. J Vet Sci Med Diagn 13:5.

Abstract

Keywords: Antioxidation ability, Captive gorillas, Branch and leaf, Feeding program

Introduction

Although wild Western Lowland Gorillas (Gorilla gorilla gorilla) have a strong preference for fruits when they are abundant, they also show a preference for young and mature leaves and bark, depending on the season. Furthermore, they consume ginger, native to wetlands, which has high antioxidant activity [1].

Currently, the standard manual for gorilla care at zoos recommends providing different types of feed, mainly plants and vegetables [2].

However, the feeding program is not focused on the antioxidant content. In addition, substantial data regarding the antioxidation ability of commercialized vegetables, fruits, dairy products and pasture grass are available; however, data on the concentrations of antioxidants in branches and leaves of various tree species in the gorilla diet are lacking. Therefore, in this study, we evaluated the concentrations of antioxidants in the branches and leaves of various tree species, including plants in different seasons, fed to Western Lowland gorillas held in captivity. Consumption was confirmed based on feeding marks on the bark and the roles of branches and leaves in gorilla captivity were considered.

Methods

For each tree species and plant part consumed based on direct observations of foraging behavior and feeding marks were sampled (approximately 300 g to 500 g). In particular, six species (Quercus myrsinifolia, Castanopsis sieboldii, Ligustrum japonicum, Quercus serrata, Zelkova serrata and Acer buergerianum) were provided to five western gorillas, one male (34 years old at the time of the survey) and four females (39 years, 34 years, 8 years and 4 years old at the time of the survey) held captive at the Ueno Zoo in Tokyo on 4 days (i.e., July 11^th, 17^th and 26^th and 17 November, 2017). The leaves were sampled with the rachis attached and the bark was sampled by scraping off using a cutter, retaining parenchymal parts. Samples for each species and plant part were sealed in plastic bags with zippers and stored at 7°C to 8°C. The antioxidant concentration was measured using the oxygen radical absorbance capacity (orac) method within 7 days after collection. The results are reported in units of μmolte/g (te, trolox equivalents) [3,4].

Results

Five gorillas were allowed to forage freely in the same enclosure. The gorilla family is free to forage in the enclosure from 9:30 to 13:15 and from 13.30 to 16.00. Between 13:15 and 13:30, the gorillas once enter the behind room, during which time vegetables, fruits, grains and abundant branches with leaves are placed around the enclosure by the keepers. At 13:30, the gorillas move back into the enclosure to eat their favorite food. In the case of mother and child, they may eat the same branches and leaves together (Figure 1).

The tree species consumed on each day were as follows; 11 July, Zelkova serrata and Quercus myrsinifolia; 17 July, Castanopsis sieboldii, Quercus serrata and Quercus myrsinifolia; 26 July, Zelkova serrata, Quercus myrsinifolia, Ligustrum japonicum, Quercus serrata and Acer buergerianum; and 17 November, Acer buergerianum, Castanopsis sieboldii and Ligustrum japonicum. Approximately 1 month prior to the survey on 17 November the 34- year-old female gave birth to a male baby. The female foraged on branches and leaves; however, the baby was held on the mother’s chest and foraging could not be observed. In addition to branches and leaves, on the day of the survey, animals fed on grass, vegetables (more than 20 types, such as broccoli, cabbage, celery, cauliflower, carrot and tomato) grains (such as barley) and small amounts of fruits and yogurt.

All the gorillas foraged on both leaves and bark that were provided on each day. In the survey in July, several branches and leaves were collected and animals sat down and ate the leaves directly using their mouth or hands; when most of the leaves were eaten, they ate the barks by gnawing. These findings indicated that there was a preference for leaves over branches. In addition, there was a difference in foraging marks on barks among tree species (Figure 2). November is the fall foliage season for deciduous trees; however, all the individuals foraged on the leaves and barks of both Zelkova serrata and Acer buergerianum.

The concentrations of antioxidants were 80 μmolTE/g to 1500 μmolTE/g in leaves and 23 μmolTE/g to 410 μmolTE/g in bark (i.e., they tended to be higher in leaves than in bark). In particular, Acer buergerianum leaves had the highest antioxidant concentration during the fall foliage season. The concentration in evergreen trees tended to be higher than that in deciduous trees (Table 1).

Table 1: Concentrations of antioxidants of feeding trees for Gorillas at ueno zoo Concentration units are μmolTE/g

Discussion

The ORAC method is an established technique endorsed by the United States Department of Agriculture (USDA) for assessing the antioxidant activities of food and various improvements to this method have been reported [5]. The ORAC method facilitates the comparison of the total antioxidant content per weight among tree species and plant components. However, it is not possible to identify the antioxidants specific to each tree species and compare the distribution; the method is limited to assessing the overall antioxidant capacity.

In a study of the antioxidant concentrations of parts of trees in the family Fagaceae, the concentrations of polyphenols, a type of antioxidant, were higher in the branches than in the leaves and pericarp [6]. Therefore, animals should be fed whole branches, rather than leaves that are cut and separated from the branches, irrespective of their preference for leaves. In addition, when the gorillas were seen gnawing the bark, they stripped the bark off lengthwise without gnawing all around the branch, including the cambium layer. However, woody plants distribute antioxidants in the inner side of the bark to protect the parenchyma and there is evidence that the bark has a higher antioxidant concentration than those of other tissues [7,8].

In addition, the ORAC value of Acer leaves in November was 20 times higher than that in July; however, anthocyanins produced during the fall foliage season may function as antioxidants [9]. It is important to understand the changes in antioxidant concentrations in leaves across seasons.

Extensive research has focused on the production and function of antioxidants in tree species, including research on antioxidant activity and function in Fagaceae species and applied research on antioxidants contained in nuts of Quercus [10,11]. Using these findings as a reference, we believe that information on the amounts of branches and leaves collected by animals in captivity, not limited to gorillas, will enable us to quantitatively understand dietary antioxidants.

In the widely recommended gorilla care manual, branches are regarded as environmental enrichment elements and manipulative objects, e.g., for bedding [2]. However, if the bark introduced as bedding material is eaten, it may also contribute to antioxidant activity in animals. For branches and leaves provided as food to animals in captivity in zoos in Japan, in addition to studying their preferences, quantitative nutrient analyses have been performed [12]. In the future, detailed analyses of antioxidants are needed.

Acknowledgements

We would like to express our gratitude to the Ueno Zoological Gardens and its gorilla keepers for their cooperation to this study.

Funding

This work was supported by JSPS KAKENHI (2016) Grant Number JP16K01202.

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