Comparative Study on 15-Ketodihydro-PGF 2a Plasma Concentrations in Newborn Horses, Donkeys and Calves S Panzani 1 , A Carluccio 2 , M Probo 1 , M Faustini 3 , H Kindahl 4 and MC Veronesi 1 1 Department of Veterinary Clinical Sciences, Faculty of Veterinary Medicine, Universita` degli Studi di Milano, Milan, Italy; 2 Department of Veterinary Clinical Sciences, Faculty of Veterinary Medicine, University of Teramo, Teramo, Italy; 3 Department of Veterinary Sciences and Technologies for Food Safety, Faculty of Veterinary Medicine, Universita` degli Studi di Milano, Milan, Italy; 4 Department of Clinical Sciences, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, Uppsala, Sweden Contents The aim of this study was to compare the plasma profiles of 15-ketodihydro-PGF 2a (PGM) in healthy neonates of three different species from birth until the third week of life. Twenty- four horse foals, 12 donkey foals, and 9 calves were studied. Blood samples were collected at 10, 20 and 30 min after birth, at 3, 24 and 72 h after birth, and at 7, 10, 17 and 21 days of life. All mothers experienced normal gestation lengths and normal, spontaneous deliveries. All newborns were judged mature and viable. Hormone concentrations were higher (p < 0.05) in horse foals 20 and 30 min after birth compared to later samples, and at 10 min in donkey foals compared to later samples (p < 0.05). In calves, higher (p < 0.05) concen- trations of PGM were observed 10, 20, 30 min and 3 hours from parturition compared to later samples. These findings may be related to increased fetal placental unit production during parturition, while the relatively high PGF 2a levels in the days after parturition may be connected with their role in completing organ maturation. Despite the existing differences between these species, the statistical analysis did not discover significant differences in PGM profiles during the first 3 weeks of life in donkey, horse and cattle newborns. The low levels observed 10 days after birth are possibly due to a fast completion of maturational development in these species. Introduction The transition from fetal to neonatal state involves three phases: late gestation, parturition, and the establishment of independent homeostatic regulation following pla- cental separation. The first hours of life are character- ized by changes in respiration, circulation, glucose homeostasis and by the onset of independent oral feeding and thermoregulation. These stages are regu- lated by a series of fetal and placental endocrine events involving several hormones and factors (Gluckman et al. 1999). Among these, the prostaglandins (PGs) play a major role during parturition and in the final multi-system maturational processes of the newborn, but their exact pattern is poorly understood (Skinner and Challis 1985; Challis et al. 1997; Ousey 2004, 2006; Panzani et al. 2009). Prostanoids act upon the fetus, influencing fetal well- being and adaptation after birth. They contribute to the development of the fetal hypothalamic-pituitary-adrenal axis (Kitterman 1987), and are involved in the matura- tion and function of various systems (Pace-Asciak 1978). For example, PGs operate at the cardiovascular and respiratory systems levels, regulating the tone of the ductus arteriosus and of the tracheobronchial tree (Friedman and Demers 1978; Mitchell et al. 1978; Reznichenko et al. 1993). They also contribute to kidney development, regulating perfusion and glomer- ular filtration rate and controlling water and electrolyte balance (Antonucci et al. 2007). PGs also play impor- tant control on hemodynamic, fluid and electrolyte homeostasis (Friedman and Demers 1980; Benzoni et al. 1981). Both PGE and PGF significantly increased in umbil- ical plasma after the onset of labour because of the fetal placental unit production (Saeed et al. 2003). Human neonates born at term display high PG concentrations, with a rapid decrease after birth in the circulating levels of prostaglandin E but not of prostaglandin F (PGF) and 15-ketodihydro-PGF 2a (PGM) (Mitchell et al. 1978). These high levels at birth could be related to fetal placental unit production, leading to an increase in the umbilical PG concentration compared to maternal plasma concentration (Saeed et al. 2003). In newborn foals, plasma PGM concentrations increased from 10 min to 20 and 30 min after parturition, then consis- tently declined to levels <100 pmol ⁄ l at 10 days after birth, remaining low until 21 days of life (Panzani et al. 2009). The higher concentrations of PGF 2a in the days after parturition compared to adults could be explained by their role in completing organ maturation (Panzani et al. 2009). Donkeys, horses and cows are monotocous charac- terized by important differences in placentation and in peripartal plasmatic changes of PGs. In mares, the birth of live horse fetuses is associated with an increase in PG concentrations in both fetal and maternal plasma during the last two hours before parturition (Barnes et al. 1978). PGs begin to increase up to 50 nmol ⁄ l during the first stage of labour, and continue to rise up to 250 nmol ⁄ l during the second stage (Barnes et al. 1978; Ousey 2004, 2006). To our knowledge, only one study has been carried out on endocrine changes during peripartum in the jenny (Veronesi et al. 2007); PGs were high during the last 10 days of pregnancy (11.7– 18.6 nmol ⁄ l) and declined on the day of parturition (1.5 nmol ⁄ l) (Veronesi et al. 2011). Finally, cows’ PGM levels markedly increased at the end of pregnancy and around parturition (13.7–21.2 nmol ⁄ l), then declined, but the release continued for several postpartum days (Edqvist et al. 1978; Konigsson et al. 2001). To date, many investigations are performed in the horse, while few studies have been conducted on the physiology of reproduction in the donkey. It should be stressed that the donkey is not just a smaller horse, but Reprod Dom Anim 47, 82–86 (2012); doi: 10.1111/j.1439-0531.2011.01804.x ISSN 0936-6768 Ó 2011 Blackwell Verlag GmbH