Animal Reproduction Science 130 (2012) 51–56 Contents lists available at SciVerse ScienceDirect Animal Reproduction Science journal homepage: www.elsevier.com/locate/anireprosci p- and m-Cresols emitted from estrous urine are reliable volatile chemical markers of ovulation in mares Raimondas Moz ¯ uraitis a,b,∗ , Vincas B¯ uda b,c , Jonas Kutra d , Anna-Karin Borg-Karlson a a Ecological Chemistry Group, Division of Organic Chemistry, Department of Chemistry, School of Chemistry and Engineering, Royal Institute of Technology, Teknikringen 36, SE-10044 Stockholm, Sweden b Laboratory of Chemical and Behavioural Ecology, Institute of Ecology, Nature Research Centre, Akademijos 2, LT-08412 Vilnius, Lithuania c Centre for Ecology and Environmental Studies, Faculty of Natural Sciences, Vilnius University, M.K. ˇ Ciurlionio 21/27, LT-03101 Vilnius, Lithuania d The Institute of Animal Science, Lithuanian University of Health Sciences, R. ˇ Zebenkos 12, LT-82317 Baisogala, Radviliˇ skis distr., Lithuania a r t i c l e i n f o Article history: Received 4 June 2011 Received in revised form 8 December 2011 Accepted 14 December 2011 Available online 29 December 2011 Keywords: Phenolic Equus cabalus Horse Estrus Headspace SPME a b s t r a c t Urine samples from 14 mares, belonging to five breeds, were collected at estrus and diestrus to search for estrous specific volatile compounds which could be used to determine ovulation time. Around 150 volatiles were collected from urine head-space samples by solid phase micro extraction technique, and analyses were conducted by gas chromatography–mass spectrometry methods. Comparison of chromatographic profiles of volatile substances revealed that concentrations of m- and p-cresols were significantly greater during estrus while diethylphthalate was more abundant at diestrus. Monitoring of m- and p-cresols during the period of estrus and a few days before and after estrus revealed irregular changes in amounts of cresols until 3–4 days before ovulation when the concentration of the compounds began to increase with peaks 1 day before ovulation. On the day when ovulation occurred, amounts of the metabolites decreased sharply, almost to basal concentrations, and remained at these concentrations for 6 days – when sampling was finished. In four of the mares changes in the concentration of diethylphthalate were less pronounced and more temporally variable compared with those of cresols. Based on reproducible temporal changes in concentrations of m- and p-cresols, with respect to the time of ovulation, a noninvasive test to determine a precise insemination time could occur. This would save time, reduce costs and simplify the procedure. © 2012 Elsevier B.V. All rights reserved. 1. Introduction During the last decade the interest in horse riding has increased remarkably in Europe. The number of horses relative to population ranges from around three horses per 1000 inhabitants in Portugal and Greece, to nearly ∗ Corresponding author at: Ecological Chemistry Group, Division of Organic Chemistry, Department of Chemistry, School of Chemistry and Engineering, Royal Institute of Technology, Teknikringen 36, SE-10044 Stockholm, Sweden. Tel.: +46 8790 8092; fax: +46 8791 2333. E-mail addresses: raimis@kth.se (R. Moz ¯ uraitis), vinbuda@ekoi.lt (V. B¯ uda), genimpeksas@yahoo.com (J. Kutra), akbk@kth.se (A.-K. Borg-Karlson). 30 horses per 1000 inhabitants in Denmark and Sweden (Haring, 2005). A growth in equestrian sports has also been observed with a special interest in breeding elite animals. Artificial insemination is the dominant biotechnology in horse reproduction because, in addition to other advan- tages, it allows breeders to inseminate mares with sperm from elite stallions without transporting animals great dis- tances to do so (Aurich and Aurich, 2006). Mares come into estrus several times a year, i.e. horses are a seasonal polyestrous species. A mare is sexually recep- tive toward a stallion for 5–7 days and ovulation occurs in the final 24–48 h of estrus (Kiley-Worthington, 1987). The greatest probability of successful fertilization is achieved when artificial insemination is performed within a period 0378-4320/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.anireprosci.2011.12.008