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>
	<li>Morm&#232;de, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exploration+of+the+hypothalamic-pituitary-adrenal+function+as+a+tool+to+evaluate+animal+welfare.">Exploration of the hypothalamic-pituitary-adrenal function as a tool to evaluate animal welfare.</a> Physiology and Behaviour. 92 (3), 317-339 (2007).</li><li>Lane, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Can+non-invasive+glucocorticoid+measures+be+used+as+reliable+indicators+of+stress+in+animals?.">Can non-invasive glucocorticoid measures be used as reliable indicators of stress in animals?.</a> Animal Welfare. 15 (4), 331-342 (2006).</li><li>Morgan, K. N., Tromborg, C. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sources+of+stress+in+captivity.">Sources of stress in captivity.</a> Applied Animal Behaviour Science. 102, 262-302 (2007).</li><li>Nelson, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> An introduction to behavioural endocrinology (3rd Ed). , 670-671 (2005).</li><li>Sapolsky, R. M., Romero, L. M., Munck, A. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+Do+Glucocorticoids+Influence+Stress+Responses?+Integrating+Permissive,+Suppressive,+Stimulatory,+and+Preparative+Actions.">How Do Glucocorticoids Influence Stress Responses? Integrating Permissive, Suppressive, Stimulatory, and Preparative Actions.</a> Endocrine Reviews. 21 (1), 55-89 (2000).</li><li>Macdonald, K. M., Macdonald, I. A., Bokkenheuser, V. D., Winter, J., McLernon, A. M., Mosbach, E. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Degradation+of+steroids+in+the+human+gut.">Degradation of steroids in the human gut.</a> Journal of Lipid Research. 24, 675-700 (1983).</li><li>Young, K. M., et al. <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+adrenocortical+activity+in+carnivores+by+fecal+glucocorticoid+analysis.">Non-invasive monitoring of adrenocortical activity in carnivores by fecal glucocorticoid analysis.</a> General and Comparative Endocrinology. 137, 148-165 (2004).</li><li>Merl, S., Scherzer, S., Palme, R., Mostl, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pain+causes+increased+concentrations+of+glucocorticoid+metabolites+in+horse+faeces.">Pain causes increased concentrations of glucocorticoid metabolites in horse faeces.</a> Journal of Equine Veterinary Science. 20, 586-590 (2000).</li><li>Yarnell, K., Hall, C., Royle, C., Walker, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Domesticated+horses+differ+in+their+behavioural+and+physiological+responses+to+isolated+and+group+housing.">Domesticated horses differ in their behavioural and physiological responses to isolated and group housing.</a> Physiology and Behaviour. 143, 51-57 (2015).</li><li>Wielebnowski, N., Watters, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applying+fecal+endocrine+monitoring+to+conservation+and+behaviour+studies+of+wild+mammals:+important+considerations+and+preliminary+tests.">Applying fecal endocrine monitoring to conservation and behaviour studies of wild mammals: important considerations and preliminary tests.</a> Israel journal of ecology and evolution. 53, 439-460 (2007).</li><li>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=Measuring+fecal+steroids:+guidelines+for+a+practical+application.">Measuring fecal steroids: guidelines for a practical application.</a> Annals of the New York Academy of Sciences. 1046, 75-80 (2005).</li><li>Uden, P., Rounsaville, G. 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. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+versatile+enzyme+immunoassay+for+non-invasive+assessment+of+glucocorticoid+metabolites+in+a+diversity+of+taxonomic+species.">Development of a versatile enzyme immunoassay for non-invasive assessment of glucocorticoid metabolites in a diversity of taxonomic species.</a> General Comparative Endocrinology. 186, 16-24 (2013).</li><li>Touma, C., 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=Measuring+fecal+glucocorticoid+metabolites+in+mammals+and+birds:+the+importance+of+validation.">Measuring fecal glucocorticoid metabolites in mammals and birds: the importance of validation.</a> Annals of the New York Academy of Sciences. 1046, 54-74 (2005).</li><li>Millspaugh, J. J., Washburn, B. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+fecal+glucocorticoid+metabolite+measures+in+conservation+biology+research:+considerations+for+application+and+interpretation.">Use of fecal glucocorticoid metabolite measures in conservation biology research: considerations for application and interpretation.</a> General and Comparative Endocrinology. 138, 189-199 (2004).</li></ol>

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, ...

The overall goal of this procedure is to demonstrate how adrenal activity can be assessed non-invasively in equines through the extraction and analysis of fecal glucocortocoid metabolites. This method can help us answer key questions in the area of welfare assessment by looking at the physiological impacts of husbandry protocols on domestic horses, all the way through to wild populations of African zebras. The main advantage of this technique is it offers a non-invasive option for measuring the long-term adrenal activity in both domestic and free-ranging horses.On the day of the experiment, after thawing at room temperature, manually homogenize the fecal samples by mixing within each individual sample bag. Then, for each sample, measure out the appropriate amount of feces on a micro balance in a clean weigh boat, and transfer the samples into individual eight milliliter glass vials. Next, mix five milliliters of 90%methanol in water with each sample, and shake the samples overnight on an orbital shaker at room temperature.The following morning, vortex the samples and spin them down. At the end of the centrifugation, decant the methanol fractions into individual 16 by 125 millimeter glass tubes. Then briefly place the tubes in a 37-degree Celsius water bath, followed by evaporation of the methanol under air in a fume cupboard.When all of the methanol has dispersed, resuspend the fecal extracts in one milliliter of 100%methanol. Then transfer the extracts into individual 12 by 75 millimeter polypropylene tubes, cap the tubes, and store the samples at minus 20 degrees Celsius until their analysis. Before beginning the analysis, use a repetitive pipette with a 50 microliter pipette tip to load 50 microliters of polyclonal corticosterone CJM006 antiserum, diluted in coating buffer, per well, in a 96 well microtiter plate.Then cover the plate with a plate sealer and incubate the antiserum overnight at four degrees Celsius. The next day, immediately before beginning the analysis, use an automated microtiter plate washer to wash the plate five times with wash solution. Then load the nonspecific binding and zero wells with 50 microliters of enzyme-linked immunoassay, or EIA buffer, per well, the standard wells with the appropriate concentrations of corticosterone, and the experimental wells with the fecal extract samples diluted in EIA buffer.After loading the last sample, immediately add 50 microliters of horseradish perodixase conjugate diluted in EIA buffer to each well, and incubate the microtiter plate in the dark for two hours at room temperature. At the end of the incubation, wash the plate with wash solution five times. Then incubate the samples with 100 microliters per well of freshly prepared, room temperature substrate in the dark at room temperature, with periodic reading of the plate at 405 nanometers on a spectrophotometer.The incubation is considered complete when the optical density of the zero wells reaches 0.8 to 1.0. To perform a biochemical validation for parallelism, perform a serial dilution on pooled fecal extracts, ideally taken from suspected high-and low-hormone concentration samples from several individuals. Then run the samples on the EIA as just demonstrated.A parallelism is considered achieved when the serial dilutions of the fecal extracts yield a displacement curve parallel to the standard curve, and the linear regression results demonstrate an R squared greater than 0.9, a slope greater than 0.5, and a P less than 05. To perform a biochemical validation for interference, spike 200 microliters of serial diluted standards with 200 microliters of the appropriate pooled fecal extract, diluted at the 50%binding as determined by the parallelism assay. Then run the samples on the EIA as demonstrated.Following the EIA analysis, plot the observed concentration minus the background concentration of the zero sample versus the expected concentration. No interference is considered achieved if the addition of diluted pooled fecal extract to the standards does not significantly alter the amount expected, and linear regression results yields R squared greater than 0.9, a slope close to one, and P less than 05. To perform a biological validation, run samples extracted before, and after a challenging event on the EIA as just demonstrated.The biological validation is a critical step for the validation of EIA, and is considered achieved when a significant rise in glucocorticoid metabolites is observed after a challenging event. The data in graph A and B demonstrate the biochemical validation of adult male and female domestic horses, by demonstrating parallelism with a corticosterone standard curve. No biochemical validation with the cortisol EIA was achieved, as there was no parallelism between the pooled fecal extract and the cortisol standard curve.These data from challenged male and female domestic horses demonstrate biological validation, as the concentration of fecal corticosterone increased as the level of isolation increased in these animals. Indeed, the horses in the isolated housing situation exhibited significantly higher levels of fecal corticosterone, compared to all of the other housing designs. So assessing hormone concentrations in saliva or plasma usually involves us looking at the native hormone, but when we're assessing it in fecal material, we're looking at a breakdown of that product and looking at the metabolic end products of that hormone.Indeed, fecal sampling offers a pooled glucocortocoid concentration over time, rather than the single point reflected by saliva or plasma. This makes it more appropriate for measuring long term, chronic or seasonal adrenal activity. So as fecal sample collection is non-invasive to the animal, it's been used extensively to monitor equine adrenal activity in numerous natural and experimental circumstances.When running EIA, it is important to minimize the time of loading the microtiter plate to under 10 minutes, as longer times will result in drift. It is also important to ensure that duplicate samples have a coefficient of variation of less than 10%and controls have an intra-and inter-assay coefficient variation of 10%and 15%respectively. So after watching this video, you should have a really good understanding of how to extract fecal glucocortocoid metabolites, analyze those extracts in an enzyme immunoassay, and also perform the required validation steps.

fecal-glucocorticoid-analysis-non-invasive-adrenal-monitoring

Research

JoVE Journal

Biology

9.5K vistas.  Nottingham Trent University. The overall goal of this procedure is to demonstrate how adrenal activity can be assessed non-invasively in equines through the extraction and analysis of fecal glucocortocoid metabolites. This method can help us answer key questions in the area of welfare assessment by looking at the physiological impacts of husbandry protocols on domestic horses, all the way through to wild populations of African zebras. The main advantage of this technique is it offers a non-invasive option for measuring t...