Potential bio-indicators for assessment of mineral status in elephants

Abstract

The aim of this study was twofold: (1) identify suitable bio-indicators to assess elemental status in elephants using captive elephant samples, and (2) understand how geochemistry influences mineral intake. Tail hair, toenail, faeces, plasma and urine were collected quarterly from 21 elephants at five UK zoos. All elephant food, soil from enclosure(s), and drinking water were also sampled. Elemental analysis was conducted on all samples, using inductively coupled plasma mass spectrometry, focusing on biologically functional minerals (Ca, Cu, Fe, K, Mg, Mn, Na, P, Se and Zn) and trace metals (As, Cd, Pb, U and V). Linear mixed modelling was used to identify how keeper-fed diet, water and soil were reflected in sample bio-indicators. No sample matrix reflected the status of all assessed elements. Toenail was the best bio-indicator of intake for the most elements reviewed in this study, with keeperfed diet being the strongest predictor. Calcium status was reflected in faeces, (p 0.019, R 2 between elephant within zoo-0.608). In this study urine was of no value in determining mineral status here and plasma was of limited value. Results aimed to define the most suitable bio-indicators to assess captive animal health and encourage onward application to wildlife management. Formulation of an appropriate zoo diet requires husbandry skills and applied nutritional science 1. Although there is limited agreement in the literature, the use of appropriate bio-indicators to assess elemental status was suggested by Combs et al. 2 to support evidence-based zoo diet assessment. Zoos in the United Kingdom have a responsibility to provide appropriate nutrition to all animals within their care 3 to prevent nutritional-related disease, compromised welfare and potential reproductive failure. Limited information exists for estimated mineral requirements of elephants 4 , with cases of specific mineral deficiency documented. Due to elephants' low growth rate and large size, clinical signs of nutrient deficiency may go unnoticed for long periods of time 5 , making nutritional evaluation challenging. Jansman and Pas (2015) 6 defined mineral status as the balance between dietary intake of a nutrient and its requirement in the body. Twenty-eight "essential" mineral elements have known metabolic roles in the mammalian system, for which dietary deficiency will lead to clinical deficiency. These include calcium (Ca), phosphorus (P), magnesium (Mg), selenium (Se) and zinc (Zn) 7,8. Minerals are utilized within the body in various forms or individual compartments, with a central reserve or interchange compartment, usually blood and one or more storage compartments, usually bone or liver. Element and animal species affects the speed of mobilisation of the mineral between compartment(s) 7,8. Mineral status can also be altered by interactions between dietary components; for example an increase in dietary P causes a decrease in serum Ca 9,10 , and variations in individuals' metabolism, circadian patterns and pathological state. Analysing elemental sta...

Method development to characterise elephant tail hairs by LA-ICP-MS to reflect changes in elemental chemistry

“…Additionally, samples from UK zoo elephants ( n = 2) were used in method development, and for further examination of the structure of the hair; collected as per methods described in Sach, Dierenfeld, et al ( 2020 ).…”

“…Sectioned elephant tail hair samples were also digested using a MARS Express closed vessel microwave heating system, with HNO 3 :4 ml/H 2 O 2 :1 ml and heated to 100 °C over 5 min, held for 1 min and then heated to 200 °C over 5 min and held for 30 min as described in Sach et al ( 2020 ).…”

“…In human and horse hair, relative concentrations of certain biologically required elements or potentially toxic elements (PTEs), varied down the hair, reflecting changes in dietary intake over time (Armelin et al, 2003 ; Bencko, 1995 ; Combs, 1987 ; Middleton et al, 2016 ). Sach, Dierenfeld, et al ( 2020 ) demonstrated that elephant tail hair is a reliable indicator of Fe and As intake and thus proxy for status, in African ( Loxodonta africana) and Asian elephants (Elephas maximus) in UK zoos. Given an approximate growth rate for a typical wild elephant hair of 0.56 mm/day (± 0.11) in males and 0.81 mm/day (± 0.13) in females, based on two studies of 32 and 50 elephant hairs, respectively, (Cerling et al, 2004 ; Wittemyer et al, 2009 ) an elephant hair of 30 cm length has the potential to indicate mineral and PTE status over a 12–18 month time period.…”

Pelos de cauda como biomonitor não invasivo da composição mineral da carne bovina

“…O mecanismo comumente utilizado para a monitoração do status mineral dos animais é o exame de sangue, porém, esse método reflete apenas as condições do organismo animal no momento da coleta. Baseado em estudos realizados com humanos e outras espécies de animais (MC DOWELL et al, 1982;ARMELIN et al, 1998;PATRA et al, 2006;BODE et al, 2008;BATISTA et al, 2009;GUO et al, 2010;ROUG et al, 2015a;SZIGETI et al, 2015;HOLASOVÁ;PECHOVÁ;HUSAKOVÁ, 2017;TREU et al, 2018;SACH et al, 2020;RUDNICKI-VELASQUEZ et al, 2021), a utilização dos pelos como matriz analítica pode ser um método alternativo para a avaliação do conteúdo mineral no organismo de bovinos. Os pelos possuem grande valor biológico devido ao potencial de acumular informações ao longo do tempo.…”

“…Estudos ecotoxicológicos realizados porTreu et al (2018) buscaram correlacionar as concentrações de Hg encontradas no tecido e no pelo de raposas do ártico da Islândia. O pelo da cauda foi utilizado como um potencial bioindicador para avaliação do status mineral em elefantes em pesquisas realizadas porSach et al (2020), buscando identificar a matriz biológica que mais refletisse a ingestão elementar desses animais Rudnicki-Velasquez et al (2021). avaliaram a bioacumulação de210 Po nos pelos de gatos de várias raças buscando determinar se fatores como raças, comprimento dos pelos, sexo, idade, peso e alimentação influenciam nas concentrações desse radionuclídeo.…”