Early pregnancy diagnosis in sheep using near-infrared spectroscopy on blood plasma

The objective of this study was to evaluate the ability of near-infrared reflectance spectroscopy (NIRS) to discriminate between pregnant and nonpregnant ewes in early stages of pregnancy after artificial insemination (AI) from blood plasma. Samples were collected using jugular puncture at 18 and 25 days after AI from 188 Rasa Aragonesa and Ansotana ewes. Plasma samples were analyzed for pregnancy-associated glycoprotein (PAG) and progesterone (P4) using ELISA commercial kits. The spectra of plasma samples were recorded in the visible and near-infrared ranges. The performance of these tests were compared, using as criterion standard the pregnancy status determined using transabdominal ultrasonography at 45 days after AI. Pregnancy rate was 47.9% (90/188). At Day 18, sensitivity was similar in NIRS and P4 tests (98.9% vs. 100%; not significant) and greater than PAG (32.2%; both P < 0.001). Specificity was similar in NIRS and PAG tests (both 100%) and greater than that of P4 (84.7%; P < 0.001). At Day 25, sensitivity and specificity of NIRS and PAG were both 100%. It can be concluded that NIRS was an accurate method of diagnosis of pregnancy at Days 18 and 25 after AI in ewes. (C) 2014 Elsevier Inc. All rights reserved.

This study was funded by the Government of Aragon (Research Group on Improvement of Sheep Production). ELISA kits for pregnancy-associated glycoprotein determination were given by Prof. J.F. Beckers, Université de Liège. The authors thank Pilar Sánchez and María Ángeles Legua for their technical collaboration. An Spanish application patent related to the present research “Procedimiento de identificación de animales gestantes” with application number P201331294 has been filed the 2nd September of 2013

Early pregnancy diagnosis

Ewe

Fertility

NIRS

PAG

Progesterone

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