A novel approach to comparing reproductive stage serum profiles in mares using near infrared spectroscopy (NIR) and aquaphotomics

Authors: AGCANAS, LAUREN - Mississippi State University; COUNSELL, KRISTEN - Mississippi State University; Shappell, Nancy; BOWERS, SUSAN - Mississippi State University; RYAN, PETER - Mississippi State University; WILLARD, SCOTT - Mississippi State University; VANCE, CARRIE - Mississippi State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/10/2016
Publication Date: 1/14/2017
Citation: Agcanas, L.A., Counsell, K., Shappell, N.W., Bowers, S., Ryan, P., Willard, S.T., Vance, C.K. 2017. A novel approach to comparing reproductive stage serum profiles in mares using near infrared spectroscopy (NIR) and aquaphotomics [abstract]. Reproduction, Fertility and Development. 29(1):117.

Interpretive Summary: .

Technical Abstract: The capability of near infrared spectroscopy (NIR) to detect biomolecules in aqueous solutions, a sub-field of NIR called Aquaphotomics, has yet to be fully explored. Aquaphotomics references water absorbance patterns and wavelength shifts in the 1st overtone of the water spectrum as they change patterns with solute composition and concentrations. Recently, NIR was used as a rapid method for detecting estrus in Holstein raw milk and for monitoring reproductive stages in urine of the Bornean Orangutan (Pongo pygmaeus) and the giant panda (Ailuropoda melanoleuca). NIR detects bond vibrations from organic molecules and water to create unique absorbance patterns, which are used to profile complex mixtures of biomolecules. The objectives of this study are to 1) characterize serum NIR spectral profiles for estrus, metestrus and diestrus in mares, and 2) determine if NIR can accurately decipher these reproductive phases from serum due to the biochemical effects of reproductive hormones. Mare estrus cycles were assessed every other day by ultrasound and serum hormone analysis. Serum was collected via jugular venipuncture on day 0, 2, 4, 8, and 16 of each cycle for three consecutive cycles from each mare. Radioimmunoassay analysis of reproductive hormones E2 and P4 was used to validate and characterize the NIR spectra. Spectra were collected from triplicate samples of 200 µl serum in a 1mm path length quartz cuvette with an ADS FieldSpec®3 spectrophotometer, at room temperature (22°C). Chemometric analysis (Unscrambler® X vs.10.4; CAMO Software) included pretreatment with a Savitsky-Golay 2nd derivative function for visual inspection of spectral features and Principal Component Analysis (PCA), after Mean centering, for distinction of reproductive status. Spectral peaks at 1347nm, 1367nm and 1465nm were unique to serum collected from mares in estrus exhibiting high E2 (11.87 - 16.88 pg/ml). Early metestrus is characterized by prominent spectral peaks at 1383nm and 1437nm corresponding to E2 levels (0.02 - 5.29 pg/ml) and P4 levels (0.02 - 3.61 ng/ml). Diestrus peaks were found at 1342nm, 1426nm and 1473nm when P4 levels ranged from 5.14 - 9.60 ng/ml. In our PCA models, 98% of the total variance in serum spectra between any pair of reproductive phases was described in only three spectral PCs, (PC1 = 83-86%, PC2 = 9-10%, PC3 = 2-5% of total variance). The PCA scores separated into distinct groups indicating clear spectral profiles describing each reproductive phase uniquely. In conclusion, PCA analysis and spectral variances indicate NIR, specifically aquaphotomics, has the theoretical capability to discriminate complex mixtures of biomolecules present in mare serum during estrus, metestrus, and diestrus reproductive states.