3.6.4 pH characteristics
Table 3.37 shows the range of published values for other primate species. There was no published data for New World primates to permit a comparison.
Table 3.37 Published pH characteristics relating to primate geophagy since 1999.
Reference Ape species samples pH
Aufreiter et al. (2001) Pan troglodytes schweinfurthii eaten 6.09-7.41 control 5.01-5.97 Ketch et al. (2001) Pan troglodytes schweinfurthii eaten 6.1-6.7 control 5.0-5.3 Klein et al. (2008) Pan troglodytes schweinfurthii N/D
Mahaney et al. (1999) Pan troglodytes schweinfurthii eaten 6.02-8.57 control 5.01-6.15 Mahaney et al. (2005) Pan troglodytes schweinfurthii eaten 5.44-6.12 control 5.4-6.16 Reference Old world species Eaten samples Particle sizes Mills et al. (2007) Papio ursinus N/D
Pebsworth et al. (2012) Papio cynocephalus ursinus eaten 9.4-9.8
Pebsworth et al. (2013) Papio cynocephalus ursinus eaten 10.1 non eaten 10.3 Voros et al.(2001) Macaca radiata N/D
Wakibara et al. (2001) Macaca fuscata N/D
The Santa Rosa samples consumed by the Ateles have pH ranges 6.12-6.24, little different from the control sites (Section 3.5.7 Table 3.27) whereas the single site eaten by the Cebus was pH 5.28. All of the Santa Rosa samples have a negative ΔpH value. Δ pH = pH(KCl) – pH (H2O), suggesting that the particles have a net negative charge. This would allow them to behave as a buffer (Ngole et al. 2010). The ΔpH value of -0.43 the Cebus site is categorised as strongly acidic, suggesting it would have a lower buffering capacity.
Folivore stomach pH needs to be at a relatively high pH to sustain their symbiotic bacteria and mitigate the effects of over production of volatile free fatty acids (Krishnamani et al. 2000).
Commonly, exchangeable aluminium is present if the KCl pH ≤ 5.2 (Natural Resources Conservation Service 2004). This is the case for Sites 2, 4, 9 and 10 Table 3.29. Antacid properties are related to the ability to neutralise acidity, reduce acid secretion and to interactions with the glycopeptides of the mucous layer at acid pH. The measured pHKCl suggests that there will be Al3+ ions released from clay minerals or Al oxides in the Santa Rosa geophagy samples. Al3+ ions have been shown to increase synthesis of protective prostaglandins which increase mucus gel viscosity and bicarbonate secretion by gastric mucosa (Lacy et al.
1982). Aluminium salts are found in many pharmaceutical antacid preparations (Krishnamani et al. 2000).
However Tennant et al. (2008) established a clear role for gastric acid in reducing susceptibility to infection with ingested bacterial pathogens, therefore elevating pH, by neutralising HCl in the stomach may be deleterious under some circumstances.
There may also be disadvantages to buffering/pH changes caused by ingesting such materials. Cation solubility, including Fe, falls as pH rises. Any rise in pH will therefore reduce the dissolution of Fe and so reduce bioavailability even where samples levels are high (Young et al. 2008). Too little acid can interfere with the absorption of iron, calcium, vitamin B12, as well as predispose to enteric infection, bacterial overgrowth, and gastric malignancy (Schubert 2007).
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In summary:The samples may, through the release of Al3+, have potentially beneficial or deleterious effects for the monkeys, depending upon the amount consumed and the circumstances of consumption.
3.6.5 Antibacterial activity
Recently there have been several publications citing the properties of clay minerals as alternatives to antibiotics in treating various different types of bacterial infections (Haydel et al. 2008, Vondruskova et al. 2010, Williams et al. 2010, Williams et al. 2011, Otto et al. 2013). Alternatively soil organisms are a common source of antibiotics (Smith 2000, Ketch et al. 2001). Antimicrobial screening of geophagy material did not detect the presence of any bacteria or fungi which may have produced antibacterial growth inhibiting compounds. The results for the LOI analysis (Figure 3.19) together with evidence from the IR analysis (Figures 3.33a-b) suggest that there is minimal if any organic material present in the samples. With the exception of Sites 7A, 7B and 8 the LOI values are all below 5%. A Low level of organic carbon introduces errors which may prevent reliable quantitative comparisons (Santisteban et al. 2004). The very small sample size available together with the effect of sample variation errors may have introduced errors in LOI determinations.
A direct antibacterial activity of aqueous leachate through the activity of exchangeable ions has been reported (Otto et al. 2010, Williams et al. 2010, Williams et al. 2011, Otto et al. 2013).
The ability of clays to bind to siderophores and other iron-chelating agents has been reviewed by Siebner-Freidbach et al. (2004) and Maurice et al. (2009). The interaction of the geophagy samples with Fe (Figures 3.70-3.71) show that samples have the potential to lower Fe levels in the GI tract. There are two principal mechanisms involved in the Fe losses, ion exchange and formation of Al/Fe insoluble complexes..
Bacteria have several mechanisms for Fe uptake which facilitates survival at different life stages e.g.
Escherichia coli, Pseudomonas aeruginosa, Salmonella spp. and Klebsiella pneumoniae use secreted siderophores to scavenge host iron. Siderophores are low molecular weight catechol or hydroxamate compounds with a high affinity for iron, which effectively compete for host Fe (Wilson et al. 1998). In order to adhere to mucosal surfaces Trichomonas synthesise surface adhesins and cyto-adherence molecules.
Production is increased in the presence of a high level of iron. Virulence is increased by several mechanisms in the presence of iron (Wilson et al. 1998) and Trichomonads grown in iron deficient media lose their virulence (Glanfield et al. 2007). Limitation of availability of Fe is a possible mechanism for reducing bacterial growth and subsequent colonisation or infection by prevention biofilm formation (Maurice et al. 2009). These mechanisms could reduce the local production and prevent diffusion and subsequent adsorption of enterotoxins and hence systemic or local toxicity and so potentially reduce the impact of an infection.
In summary:
The IR results in combination with the lack of fungal or bacterial growth makes it unlikely that there would be any source of potential antibiotic effects. The possibility of Fe adsorption may assist in limiting establishment of infective organisms or reduce infection load.
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3.6.6 Antiparasitic activity
It has been suggested that geophagic material may reduce internal parasite load e.g. geohelminths by reducing colonization of hosts (Krishnamani et al. 2000). The larger particles present in the Ateles site samples, if sand like, may exert an abrasive function on the lining of the GI tract possibly detaching or damaging the surface of attached infecting organisms, in a similar manner to the possible function for hairy leaf swallowing by chimpanzee.
Particle fractions <4μm in geophagic material may become bound into the mucosal layer effectively increasing its depth and so increasing its effectiveness. Clay minerals have been shown to increase the thickness of the mucous layer due to the interaction of mineral particles and mucous glycopeptides, increasing gastrointestinal glycopeptide polymerisation (Leonard et al. 1994, Reichardt et al. 2009). Geophagi has also been shown to induce a change in the morphology of the mucosal epithelial layer (Sayar et al. 1975). Such changes may also reduce infection by preventing the attachment and penetration into the epithelial cells of the gut wall of microorganisms and parasitic protozoa, as attachment is often the critical primary stage in infection (Nobuko et al. 2011).
The viability of infective organisms may also be reduced by interactions with clays as is reported for Histoplasma capsulatum (Lavie et al. 1986b, a). Clay and fine silt sized particles may coat the surface of infective organisms. Tapeworms, a cestode, lack an alimentary canal and so nutrients must be absorbed through the tegument The external cuticle contains negatively charged pores (15Å radius) through which it obtains water, ions and other nutrients and excretes its waste products (Thompson et al. 1995). The tegument of trematodes i.e. a fluke is metabolically active and is involved in adsorption of nutrients, osmoregulation and excretion (Smyth et al. 1987). Physical blocking of such pores by particles adhering to the cuticle would have a significant effect on viability. In this manner the smaller sized fractions may reduce the viability and hence virulence of infecting organisms and regulating parasite load. This may be the mechanism responsible for the observations reported by Knezevich (1998).
In summary:
There are several potential mechanisms related to physical effects or related to particle size which may potentially influence establishment of infections and subsequently parasite load.
3.6.7 Antidiarrhoeal activity
A reduction of fluid loss and antidiarrhoeal activity could be related to the swelling properties of clay minerals. Montmorillonite clay minerals exhibit swelling of the crystal lattice due to interlayer expansion caused by the adsorption of water. There may also be interparticular swelling which involves an increase in volume due to adsorption of water molecules between individual clay sized particles. Kaolinites, whilst not exhibiting swelling, are also capable of adsorbing water onto their exterior surface layer (Baeshad 1955).The lack of montmorillonite and low kaolinite content of the Santa Rosa samples does not preclude the geophagy samples from being used in mitigation of diarrhoea symptoms but it may have limited antidiarrhoeal activity against watery diarrhoea.
Enterotoxins are produced by many bacteria and those from organisms such as Escherichia coli, Staphylococcus aureus, Salmonella enterica, and Listeria monocytogenes may potentially have serious
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impacts on health. Toxins from these organisms can cause gastrointestinal distress (diarrhoea), dizziness, and muscle pains; at sufficiently high levels they can be mutagenic, carcinogenic, or fatal (Young et al. 2011).Changes in the properties and thickness of the mucous layer will reduce the direct effects of enterotoxins and by reducing absorption mitigate the systemic effects.
A further mechanism for reducing toxicity results from the binding potential of toxins/micro-organisms directly to the clay material and the subsequent elimination of these from the body. The mycotoxin T2 toxin (Fioramonti et al. 1987b) and toxins produced by Vibrio cholera (Fioramonti et al. 1987a) are adsorbed by clay minerals thus reducing the increased gastric motility caused by these toxins. This reduction in motility would have a beneficial effect on fluid balance.
Geophagy as an antidiarrhoeal agent has been suggested as a potential function for controlling diarrhoea induced by diet change in the predominantly folivorous mountain gorilla (Mahaney et al. 1995a).
Ingestion of food items high in soluble carbohydrates and protein and low fibre may cause digestive upsets.
Wakibara (2001) reported that the provisioned foods given to the Japanese macaques met this characteristic and suggested this may be one of the uses in this situation. Rhesus macaque ate soil at the same time on 64 occasions, with 84% of events taking place close to supplemental feed stations (Knezevich 1998). Often the monkeys still had feed in their cheeks when they ate the soil. Monkey chow traditionally has high carbohydrate and protein and low fibre (LabChows Purina® and Mazuri® Zoo feed data sheets). A reduction in geophagia was reported in lemurs when they reduced their intake of provisioned foods (Ganzhorn 1987).
Ateles at Santa Rosa had changed the major dietary fruits at the time of their geophagy (Filippo Aureli personal communication Chapter 1). During September-November the monkeys’ principal fruits are Spondias mombin and radikoferi (Table 1.1). S. mombin has a higher fructose level than other commonly eaten fruits at Santa Rosa for which published data was available (Riba-Hernandez et al. 2003). Fructose malabsorption (Andersson et al. 1978) and high fructose content of the diet have been linked to bacterial metabolism in the colon producing free fatty acids and gases causingbloating, cramp and osmotic diarrhoea (Ledochowski et al.
2010). Clay minerals and clay sized particles can adsorb free fatty acids (Theng 2012).
In summary:
Whilst the geophagy material had little potential for reducing watery diarrhoea by the adsorption of water it retains the potential to adsorb toxins or free fatty acids which are possible causes of diarrhoea. The response to altered dietary items appears to have more merit but warrants further investigation before any clear connection can be established.
3.6.8 Mineral or micronutrient supplementation
Figure 3.54 is a comparison of some nutrient elements of interest; which had values > LOQ. There is little difference between the sites suggesting the areas sampled are reasonably uniform in their composition.
Whilst the highest levels are for calcium, they are only at the µg/g level.
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Figure 3.54 Intersite comparisons of elements released in GI digest conditions
New World primates at Twycross Zoo (working on the basis of a max 2% weight/day based on 6kg adult) are provided with 42g/day Mazuri Primate® and 138g/day Mazuri Browser Breeder® pellets to supplement the fresh fruits and vegetables (Zak Showell, Personal communication).
As can be seen from Table 3.36, geophagy samples provided insignificant amounts compared to those listed in the two purchased supplements. In order to benefit from the levels of minerals released in pH2, a large amount of geophagic material would need to be consumed to have any significant contribution. This would involve eating a relatively large volume of material which would impact on food intake.
Table 3.36 Comparison of nutrient minerals in geophagic samples and commercial primate feeds used for feeding Ateles fusciceps and Ateles paniscus at Twycross Zoo, UK.
Mazuri primate®
42g/day/6kg monkey Mazuri Browser Breeder
®138g/day/6kg monkey max value geophagy samples μg/g
calcium 1.11 (g) 1.76 (g) 450
phosphorus 449 (mg) 676 (mg) < LOQ
sodium 130 (mg) 483 (mg) <LOQ
magnesium 92 (mg) 524 (mg) 163
copper 0.69 (mg) 3.27 (mg) 22
This lack of support for nutritional function is consistent with much of the published literature for primate species (Mahaney et al. 1995c, Aufreiter et al. 2001). Commonly, only minor differences in minerals and trace elements were detected between eaten and control samples (Voros et al. 2001). Material from termitaria were reported as being high in Ca, Mg, K and P (Krishnamani et al. 2000) Mn, Fe, Al, Na, Co, Zn, Cu and Ni (Setz et al. 1999). Leaf cutter ant material was reported as being high in Ti, Al, Fe, K, Zn, Ni, Cr and P but the bioavailablity was not determined (Müller et al. 1997). Pebsworth et al. (2013) reported that eaten samples were lower in Fe than rejected but that Fe had low bioavailability.
Dividing minerals into macro, micro and trace categories Krishnamai et al. (2000) suggested that macromineral levels were sufficient in primate diets and that micro and trace elements were likely to be more significant due to their essential function in enzymes and DNA and RNA synthesis. General trace element sourcing was hypothesised by (Heymann et al. 1991) and specifically Zn and Cu (Kikouama et al. 2009a, 2009b). Mills et al. (2007) reported that the largest of the lick sites analysed were enriched in micronutrients and concluded it is possible that the need for micronutrients was driving the geophagy. As previously stated the availability of the trace minerals in Santa Rosa samples of Bo, Cu, Co, Se, Mo, Se and I, did not meet LOD/LOQ criteria.
0 200 400 600 800
Site 1 Site 2 Site 4 Site 9 Site 10
µg/g released
Ca44 Mg24 Al27 Ba138 Mn55 Zn68