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.

déclaration éthique: les procédures impliquant l&#39;échantillonnage sur le terrain et les animaux sujets ont été approuvés par l&#39;École des animaux, rural et sciences de l&#39;environnement (ARES) à l&#39;Université de Nottingham Trent. 1. Prélèvement des échantillons fécaux NOTE: Les gants doivent être portés lors de la manipulation des échantillons fécaux et le méthanol. S&#39;il y a une forte suspicion que l&#39;animal pourrait souffrir d&#39;une maladie zoonotique, des vêtements...

<ol>
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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? 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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>

analyse de corticostérone Fecal fournit un moyen d&#39;évaluer les modèles à long terme de l&#39;activité des glandes surrénales chez les chevaux. La nature non-invasive de la méthode permet de surmonter les effets de confusion d&#39;autres méthodes d&#39;échantillonnage utilisées pour évaluer l&#39; activité des glandes surrénales , y compris la salive et le plasma analyse 9. En outre, la technique présente un avantage non-invasive clair si l&#39;étude des chevaux libres allant. <p class="...

La méthode décrite vise à analyser les concentrations de corticostérone dans les fèces équins afin de fournir une évaluation non invasive de l&#39;activité surrénale. Mesure de l&#39;activité (HPA) axe hypothalamo-hypophyso-surrénalien est une approche acceptée pour étudier la réponse à des situations potentiellement aversif chez les deux espèces en captivité et domestiques. La technique de référence et la méthode la plus largement utilisée est l&#39;utilisation du plasma sanguin 1 cependant, d&#39; autres méthodes telles que l&#39; analyse fécale ont été développés afin de surmonter le stress induit par le prélèvement de sang lui - même et permettre à la capacité de surveiller les espèces en liberté. Dans une situation aversif, l&#39;homéostasie physiologique est perturbé. L&#39;hypothalamus dans le cerveau libère Corticolibérine (CRH) qui agit sur l&#39;hypophyse antérieure et stimule la libération de l&#39;hormone corticotrope (ACTH). ACTH pénètre dans le sang et stimule le cortex surrénalien à sécréter espèces glucocorticoïdes spécifiques (GC). Les glucocorticoïdes sont étroitement liés à des événements stressants plutôt que d&#39; être produite de manière cohérente dans tous les états d&#39;énergie accrue par conséquent , ils sont souvent mesurés en priorité sur les autres contraintes liées hormones 2. Les glucocorticoïdes sont responsables de plusieurs effets adaptatifs chez les chevaux. L&#39; énergie est rapidement mobilisée à partir de sites de stockage dans le corps sous la forme d&#39;acides gras et de glucose, l&#39; apport en oxygène est augmentée, la fonction sensorielle est améliorée 3 et le flux sanguin est réduit dans les zones ne sont pas nécessaires pour le mouvement 4. En plus d&#39;agir comme mécanisme d&#39; adaptation, le stress hausse induite par les glucocorticoïdes peut également aider à préparer l&#39;animal pour la prochaine stresseur 5. L&#39;évaluation des niveaux d&#39;hormones dans le plasma et la salive consiste à mesurer l&#39;hormone circulante réelle cependant, la mesure des métabolites dans les mesures de fèces le produit final métabolique de l&#39;hormone. stéroïdes circulantes sont catabolized dans la lIver avant l&#39; excrétion de la bile où ils subissent d&#39; autres changements facilitées par les activités enzymatiques de la flore bactérienne intestinale dans la piste 6. Par conséquent, immunoessais dirigés vers glucocorticoïdes sanguins peuvent ne pas être adapté à l&#39; analyse des métabolites glucocorticoïdes fécaux 7. Comme la collecte fécale peut être effectuée sans perturbation du cheval, l&#39;analyse des selles pour la corticostérone, a été largement utilisé pour surveiller l&#39;activité HPA dans un certain nombre de circonstances. Corticostérone Elevated dans les selles des chevaux a été rapporté en réponse à des situations potentiellement aversif , y compris pendant le traitement vétérinaire post-opératoire 8 et dans le logement 9 restrictive. Échantillonnage fécal reflète un niveau de glucocorticoïdes mis en commun au fil du temps plutôt que le point dans l&#39; échantillonnage de temps offert par le plasma et la salive rendant approprié pour le suivi à long terme, chronique ou modèles saisonniers 10. En raison de la non-invasivenature de la méthode, des échantillons peuvent être recueillis à plusieurs reprises pour un individu sans qu&#39;il soit nécessaire de capture ou de retenue 11. Cependant, les espèces spécifiques gut temps de transit doit être pris en compte lors de la planification d&#39;un protocole d&#39;échantillonnage. Chez les chevaux, le temps de transit intestinal est d&#39; environ 18 h 12 donc, la réponse des surrénales et des métabolites de corticostérone ultérieures peuvent être détectées dans les selles un jour après l&#39; activation initiale de l&#39;axe HPA. Lors de l&#39; utilisation des techniques de dosage immunologique non invasifs une validation minutieuse pour l&#39;espèce étudiée est essentielle 13. En outre, les différences de sexe en hormone métabolite excrétion ont été rapportés probablement en raison de différences dans le taux métabolique et le type de corticostérone métabolite excrété dans diverses espèces , y compris les souris 14, et les poulets 15. Il était donc important dans le cadre de cette méthode que le test a été validé pour une utilisation à la fois mâle et chevaux domestiques comme cela est détaillé dans eProtocole e. Cette différence dans le métabolisme hormonal entre les sexes a des conséquences sur la qualité des données mais il est rarement pris en compte et inclus dans le cadre de la validation du test. Cette méthode non-invasive permet à long terme l&#39;évaluation de l&#39;activité des glandes surrénales chez les chevaux domestiques. Les détails du protocole à la fois la validation de l&#39;essai et de la technique de dosage elle-même.

<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.

chevaux domestiques (n = 16, 8 juments, 8 hongres) avec un âge moyen de 15 ans (± 3) ont été regroupés en fonction du sexe et soumis à quatre modèles de logement avec des niveaux croissants d&#39;isolement social (n = 4 cheval / traitement). Logement 1 impliqué chevaux vivant dans un environnement de troupeau, simulant étroitement leur habitat naturel. Logement 2 impliqués chevaux vivant en couple dans une grange couverte. Logement 3 chevaux impliqués logés seuls dans les éc...

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.

Fecal glucocorticoïdes Analyse: Surveillance surrénale non invasive en Equidés

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.

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