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.

declaração de ética: os procedimentos que envolvem temas de amostragem de campo e animais foram aprovados pela Escola de Animal, Rural e Ciência Ambiental (ARES) na Nottingham Trent University. 1. Recolha de amostras fecais NOTA: Devem ser usadas luvas ao manusear amostras fecais e metanol. Se existe uma forte suspeita de que um animal pode estar sofrendo de uma doença zoonótica, roupas de proteção, como também deve ser usado um jaleco. <ol><li> Recolha das amostras fecais, o mais rapidamente ...

<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>

análise de corticosterona fecal fornece um meio de avaliar os padrões de longo prazo da atividade adrenal em cavalos. A natureza não-invasiva do método supera os efeitos de confusão de outros métodos de amostragem utilizados para avaliar a atividade adrenal incluindo saliva e no plasma análise 9. Além disso, a técnica tem uma vantagem não-invasivo claro se estudando cavalos livres que vão. Há vários pontos-chave para discussão em relação a este método e seu uso ad...

O método descrito pretende analisar concentrações de corticosterona em fezes equina, a fim de fornecer uma avaliação não-invasiva da actividade supra-renal. Medir a atividade do hipotálamo-pituitária-adrenal (HPA) é uma abordagem aceite para estudar a resposta a situações potencialmente aversivas em ambas as espécies em cativeiro e domésticos. A técnica de referência e o método mais amplamente utilizado é o uso de um plasma sanguíneo no entanto, métodos alternativos, tais como a análise fecal foram desenvolvidas de modo a ultrapassar a tensão induzida por amostragem de sangue em si e permitem que a capacidade de monitorar as espécies que vão livre. Durante uma situação de aversivo, homeostase fisiológica é interrompido. O hipotálamo no cérebro libera hormônio liberador de corticotrofina (CRH), que atua na glândula pituitária e estimula a liberação de hormônio adrenocorticotrófico (ACTH). ACTH entra na corrente sanguínea e estimula o córtex adrenal a secretar speciede s glicocorticóides específicos (CG). Os glicocorticóides estão intimamente ligados a eventos estressantes ao invés de ser consistentemente produzidos em todos os estados de energia elevada, portanto, eles são muitas vezes medidos em preferência sobre outros de estresse ligado hormônios 2. Os glucocorticóides são responsáveis ​​por diversos efeitos adaptativos em cavalos. A energia é rapidamente mobilizados a partir de locais de armazenagem no corpo sob a forma de ácidos gordos e de glucose, o consumo de oxigénio é aumentada, a função sensorial é reforçada 3 e o fluxo sanguíneo é reduzido em áreas não necessárias para o movimento 4. Além de atuar como um mecanismo de enfrentamento, o aumento induzido stress na glicocorticóides também pode ajudar a preparar o animal para a próxima estressor 5. Avaliando os níveis de hormona no plasma e na saliva envolve a medição da hormona em circulação real no entanto, a medição dos metabolitos nas fezes medidas do produto final metabólico da hormona. esteróides circulantes são catabolized na lIver antes da excreção para a bílis onde sofrem mais alterações facilitados pelas atividades enzimáticas da flora bacteriana intestinal dentro da faixa 6. Portanto, imunoensaios dirigidos a glucocorticóides no sangue pode não ser adequado para análise de metabolitos fecais 7 glucocorticóides. Como recolha de fezes pode ser levada a cabo sem perturbar o cavalo, a análise de fezes para corticosterona, tem sido amplamente utilizado para monitorizar a actividade HPA num número de circunstâncias. Corticosterona elevada nas fezes de cavalos tem sido relatada em resposta a situações potencialmente aversivas, nomeadamente durante o tratamento veterinário pós-operatório 8 e em habitação restritiva 9. Amostragem fecal reflete um nível de glicocorticóides agrupada ao longo do tempo, em vez de o ponto de amostragem de tempo oferecido pelo plasma e saliva tornando-o adequado para o acompanhamento a longo prazo, crónica ou padrões sazonais 10. Devido à não-invasivanatureza do método, as amostras podem ser colhidas repetidamente para um indivíduo sem a necessidade de captura ou de contenção 11. No entanto, as espécies de tempo específico trânsito intestinal deve ser levado em conta no planejamento de um protocolo de amostragem. Em cavalos, tempo de trânsito intestinal é de cerca de 18 h, por conseguinte, 12, resposta adrenal e metabolitos subsequentes de corticosterona pode ser detectado nas fezes um dia após a activação inicial do eixo HPA. Ao utilizar técnicas de imunoensaio não-invasivos uma validação cuidadosa para a espécie a ser investigada é essencial 13. Além disso, as diferenças de sexo na excreção de metabolitos da hormona foram relatados provavelmente devido a diferenças na taxa metabólica e o tipo de metabólito excretado corticosterona em várias espécies, incluindo ratos, 14 e 15 galinhas. Foi, portanto, importante como parte deste método que o ensaio foi validado para uso em cavalos domésticos masculinos e femininos, como está detalhado no the protocolo. Essa diferença no metabolismo hormonal entre os sexos tem consequências para a qualidade dos dados, no entanto, raramente é abordada e incluído como parte da validação do ensaio. Este método não-invasivo permite a avaliação de longo prazo da atividade adrenal em cavalos domésticos. Os detalhes do protocolo tanto a validação do ensaio e da técnica de ensaio em si.

<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.

cavalos domésticos (n = 16, 8 éguas, 8 capões), com uma idade média de 15 anos (± 3) foram agrupados de acordo com o sexo e submetido a quatro projetos de habitação com níveis crescentes de isolamento social (n = 4 cavalo / tratamento). Habitação 1 envolveu cavalos que vivem em um ambiente de rebanho, simulando intimamente seu habitat natural. Habitação 2 envolvidos cavalos que vivem em pares em um celeiro interior. Habitação 3 cavalos envolvidos alojado sozinho em estábul...

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 Análise de glicocorticóides: Non-invasive Monitoring Adrenal em eqüídeos

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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