Name: fecal glucocorticoid analysis: non-invasive adrenal monitoring in equids
Uploaded: 2016-04-25T13:00:00
Description: Watch this Scientific Journal Video about Fecal Glucocorticoid Analysis: Non-invasive Adrenal Monitoring in Equids at JoVE.com

Funding for the production of this manuscript was provided by Nottingham Trent University. The authors wish to thank the University yard manager, Anna Gregory for the use of her horses and provision of fecal samples for use in the protocol. Thanks also to Chester Zoo Wildlife Endocrinology Laboratory for use of their facilities.

Ethics statement: procedures involving field sampling and animal subjects have been approved by the School of Animal, Rural and Environmental Science (ARES) at Nottingham Trent University.
1. Collection of Fecal Samples
NOTE: Gloves should be worn when handling fecal samples and methanol. If there is a strong suspicion that an animal could be suffering from a zoonotic disease, protective clothing such as a lab coat should also be worn.
<ol>
	<li>Collect the fecal samples as soon as possible (within min to...

<ol>
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R., Wiggans, G. R., Van Soest, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+measurement+of+liquid+and+solid+digesta+retention+in+ruminants,+equines+and+rabbits+given+timothy+hay.">The measurement of liquid and solid digesta retention in ruminants, equines and rabbits given timothy hay.</a> British Journal of Nutrition. 48, 329-339 (1982).</li><li>Goymann, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-invasive+monitoring+of+hormones+in+bird+droppings:+biological+validations,+sampling,+extraction,+sex+differences+and+the+influence+of+diet+on+hormone+metabolite+levels.">Non-invasive monitoring of hormones in bird droppings: biological validations, sampling, extraction, sex differences and the influence of diet on hormone metabolite levels.</a> Annals of the New York Academy of Sciences. 1046, 35-53 (2005).</li><li>Touma, C., sachser, N., Mostl, E., Palme, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+sex+and+time+of+day+on+metabolism+and+excretion+of+corticosterone+in+urine+and+feces+of+mice.">Effects of sex and time of day on metabolism and excretion of corticosterone in urine and feces of mice.</a> General and comparative Endocrinology. 130, 267-278 (2003).</li><li>Rattenbacher, S., Mostl, E., Hackl, R., Ghareeb, K., Palme, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+corticosterone+metabolites+in+chicken+droppings.">Measurement of corticosterone metabolites in chicken droppings.</a> British Poultry Science. 45, 704-711 (2004).</li><li>Yarnell, K., Hall, C., Billett, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+assessment+of+the+aversive+nature+of+an+animal+management+procedure+using+behavioural+and+physiological+measures.">An assessment of the aversive nature of an animal management procedure using behavioural and physiological measures.</a> Physiology &amp; Behaviour. 118, 32-39 (2013).</li><li>Goymann, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+use+of+non-invasive+hormone+research+in+uncontrolled,+natural+environments:+the+problem+with+sex,+diet,+metabolic+rate+and+the+individual.">On the use of non-invasive hormone research in uncontrolled, natural environments: the problem with sex, diet, metabolic rate and the individual.</a> Methods in Ecology and Evolution. 3, 757-765 (2012).</li><li>Sheriff, M. J., Dantzer, B., Delehanty, B., Palme, R., Boonstra, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+stress+in+wildlife:+techniques+for+quantifying+glucocorticoids.">Measuring stress in wildlife: techniques for quantifying glucocorticoids.</a> Oecologia. 166, 614-619 (2011).</li><li>Watson, R., Munro, C. J., Edwards, K. L., Norton, V., Brown, J. L., Walker, S. 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Fecal corticosterone analysis provides a means of assessing long term patterns of adrenal activity in horses. The non-invasive nature of the method overcomes the confounding effects of other sampling methods used to assess adrenal activity including saliva and plasma analysis9. In addition the technique has a clear non-invasive advantage if studying free ranging horses.
There are several key points to discuss regarding this method and its appropriate use. A critical step in the prot...

The method described aims to analyse corticosterone concentrations in equine feces in order to provide a non-invasive evaluation of adrenal activity. Measuring hypothalamic-pituitary-adrenal (HPA) axis activity is an accepted approach to study the response to potentially aversive situations in both captive and domestic species. The reference technique and the most widely used method is the use of blood plasma1 however, alternate methods such as fecal analysis have been developed in order to overcome the stress induced by blood sampling itself and allow the ability to monitor free ranging species.
During an aversive situation, physiological homeostasis is disrupted. The hypothalamus in the brain releases corticotrophin releasing hormone (CRH) which acts on the anterior pituitary gland and stimulates release of adrenocorticotrophic hormone (ACTH). ACTH enters the bloodstream and stimulates the adrenal cortex to secrete species specific glucocorticoids (GC). Glucocorticoids are closely linked to stressful events rather than being consistently produced in all energy heightened states therefore they are often measured in preference over other stress linked hormones2. Glucocorticoids are responsible for several adaptive effects in horses. Energy is rapidly mobilised from storage sites in the body in the form of fatty acids and glucose, oxygen intake is increased, sensory function is enhanced3 and blood flow is decreased to areas not necessary for movement4. As well as acting as a coping mechanism, the stress induced rise in Glucocorticoids may also help to prepare the animal for the next stressor5.
Assessing hormone levels in the plasma and saliva involves measuring the actual circulating hormone however, measuring the metabolites in the faeces measures the metabolic end product of the hormone. Circulating steroids are catabolized in the liver before excretion in to the bile where they undergo further changes facilitated by the enzymatic activities of bacterial flora within the intestinal track6. Therefore, immunoassays directed towards blood glucocorticoids may not be suitable for analysis of fecal glucocorticoid metabolites7.
As fecal collection can be carried out with no disturbance to the horse, analysis of feces for corticosterone, has been used extensively to monitor HPA activity in a number of circumstances. Elevated corticosterone in the feces of horses has been reported in response to potentially aversive situations including during post-operative veterinary treatment8 and in restrictive housing9. Fecal sampling reflects a pooled glucocorticoid level over time rather than the point in time sampling offered by plasma and saliva making it appropriate for monitoring long term, chronic or seasonal patterns10. Due to the non-invasive nature of the method, samples can be collected repeatedly for an individual without the need for capture or restraint11. However, species specific gut transit time must be taken into account when planning a sampling protocol. In horses, gut transit time is around 18 hr12 therefore, adrenal response and subsequent corticosterone metabolites can be detected in the feces one day after initial activation of the HPA axis.
When utilising non-invasive immunoassay techniques a careful validation for the species being investigated is essential13. In addition, sex differences in hormone metabolite excretion have been reported probably due to differences in metabolic rate and type of corticosterone metabolite excreted in various species including mice14, and chickens15. It was therefore important as part of this method that the assay was validated for use in both male and female domestic horses as is detailed in the protocol. This difference in hormone metabolism between genders has consequences for data quality yet it is rarely addressed and included as part of assay validation.
This non-invasive method allows long term assessment of adrenal activity in domestic horses. The protocol details both the validation of the assay and the assay technique itself.

<table>
	<tbody>
		<tr>
			<td>Corticosterone antibody &#38; HRP kit</td>
			<td>Coralie Munro - UC Davis</td>
			<td>NA</td>
			<td>No longer available through UC Davis - please see Arbor Assays</td>
		</tr>
		<tr>
			<td>Cortisol antibody &#38; HRP kit</td>
			<td>Coralie Munro - UC Davis</td>
			<td>NA</td>
			<td>No longer available through UC Davis - please see Arbor Assays</td>
		</tr>
		<tr>
			<td>Corticosterone synthetic standard hormone</td>
			<td>Sigma Aldrich</td>
			<td>50-23-7</td>
			<td>Harnful if ingested or with skin contact. Use in fume cupboard</td>
		</tr>
		<tr>
			<td>Cortisol synthetic standard hormone</td>
			<td>Sigma Aldrich</td>
			<td>15087-01-1</td>
			<td>Harnful if ingested or with skin contact. Use in fume cupboard</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Sigma Aldrich</td>
			<td>67-56-1</td>
			<td>Irritant. Use in fume cupboard</td>
		</tr>
		<tr>
			<td>Sodium Bicarbonate</td>
			<td>Sigma Aldrich</td>
			<td>144-55-8</td>
			<td>Irritant</td>
		</tr>
		<tr>
			<td>Sodium Carbonate Anhydrous</td>
			<td>Sigma Aldrich</td>
			<td>497-19-8</td>
			<td>Irritant</td>
		</tr>
		<tr>
			<td>Sodium Phosphate Dibasic</td>
			<td>Sigma Aldrich</td>
			<td>7558-79-4</td>
			<td>Irritant</td>
		</tr>
		<tr>
			<td>Sodium Phosphate Monobasic</td>
			<td>Sigma Aldrich</td>
			<td>10049-21-5</td>
			<td>Irritant</td>
		</tr>
		<tr>
			<td>BSA</td>
			<td>Sigma Aldrich</td>
			<td>9048-46-8</td>
			<td>Irritant</td>
		</tr>
		<tr>
			<td>Tween 20</td>
			<td>Sigma Aldrich</td>
			<td>9005-64-5</td>
			<td>Irritant</td>
		</tr>
		<tr>
			<td>Citric Acid</td>
			<td>Sigma Aldrich</td>
			<td>77-92-9</td>
			<td>Irritant</td>
		</tr>
		<tr>
			<td>ABTS</td>
			<td>Sigma Aldrich</td>
			<td>30931-67-0</td>
			<td>Irritant</td>
		</tr>
		<tr>
			<td>Hydrogen Peroxide 30%</td>
			<td>Sigma Aldrich</td>
			<td>7722-84-1</td>
			<td>Irritant</td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Sigma Aldrich</td>
			<td>7647-14-5</td>
			<td>Irritant</td>
		</tr>
		<tr>
			<td>Buffer capsules - pH 4</td>
			<td>VWR</td>
			<td>332732B</td>
			<td></td>
		</tr>
		<tr>
			<td>Buffer capsules - pH 7</td>
			<td>VWR</td>
			<td>332742D</td>
			<td></td>
		</tr>
		<tr>
			<td>Buffer capsules - pH 10</td>
			<td>VWR</td>
			<td>332762H</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrochloric Acid</td>
			<td>Sigma Aldrich</td>
			<td>435570</td>
			<td>Irritant. Use in fume cupboard</td>
		</tr>
		<tr>
			<td>Sodium Hydroxide</td>
			<td>Sigma Aldrich</td>
			<td>S5881</td>
			<td>Irritant</td>
		</tr>
		<tr>
			<td>Analytical balance</td>
			<td>Fisher Scientific</td>
			<td>BFS-525-010A</td>
			<td></td>
		</tr>
		<tr>
			<td>Air compressor</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Computer +printer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>fridge-freezer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Drying apparatus</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>+tubing</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Flammable liquid storagecabinet</td>
			<td>VWR</td>
			<td>649-002</td>
			<td></td>
		</tr>
		<tr>
			<td>Fume cupboard</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hot-plate stirrer</td>
			<td>VWR</td>
			<td>640-282</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate reader</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate washer</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>pH meter</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf Research&#174; pipettes - multipack option 2</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette - 1000ul</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette - 200ul</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette - 20ul</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Repeater pipette</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette filler</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Orbital shaker</td>
			<td>Progen Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sonicator</td>
			<td>Hilsonic</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Vortex</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Warm water bath</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Water purification system</td>
			<td>Millipore</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

fecal glucocorticoid analysis: non-invasive adrenal monitoring in equids

Adrenal activity can be assessed in the equine species by analysis of feces for corticosterone metabolites. During a potentially aversive situation, corticotrophin releasing hormone (CRH) is released from the hypothalamus in the brain. This stimulates the release of adrenocorticotrophic hormone (ACTH) from the pituitary gland, which in turn stimulates release of glucocorticoids from the adrenal gland. In horses the glucocorticoid corticosterone is responsible for several adaptations needed to support equine flight behaviour and subsequent removal from the aversive situation. Corticosterone metabolites can be detected in the feces of horses and assessment offers a non-invasive option to evaluate long term patterns of adrenal activity. Fecal assessment offers advantages over other techniques that monitor adrenal activity including blood plasma and saliva analysis. The non-invasive nature of the method avoids sampling stress which can confound results. It also allows the opportunity for repeated sampling over time and is ideal for studies in free ranging horses. This protocol describes the enzyme linked immunoassay (EIA) used to assess feces for corticosterone, in addition to the associated biochemical validation.

Domestic horses (n = 16, 8 mares, 8 geldings) with a mean age of 15 years (&#177; 3) were grouped according to gender and subjected to four housing designs with increasing levels of social isolation (n = 4 horse/treatment). Housing 1 involved horses living in a herd environment, closely simulating their natural habitat. Housing 2 involved horses living in pairs in an indoor barn. Housing 3 involved horses housed alone in stables but with visual contact to other horses and housing 4 involv...

Watch this Scientific Journal Video about Fecal Glucocorticoid Analysis: Non-invasive Adrenal Monitoring in Equids at JoVE.com

Fecal Glucocorticoid Analysis: Non-invasive Adrenal Monitoring in Equids

Adrenal activity can be assessed in the equine species by analysis of feces for corticosterone metabolites. The method offers a non-invasive option to assess long term patterns in both domestic and free ranging horses. This protocol describes the enzyme linked immunoassay involved and the associated biochemical validation.

Adrenal activity can be assessed in the equine species by analysis of feces for corticosterone metabolites. During a potentially aversive situation, ...

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