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The Mangalarga Paulista is a Brazilian horse breed that originated from a cross between Andalusian and Alter Real horses, and despite its national importance, no data exist regarding their gestational length. This study was conducted to determine the variation in gestation length and the influence of factors such as the sex of the foal, maternal age and parity, stallion and mating period. Retrospectively, data from 208 gestations of Mangalarga Paulista foals located in Piracaia, SP, Brazil, during the period from 1991 to 2012 were analyzed. The mean gestational length was 343.08 ± 0.66 days, with a range between 317 and 404 days. Gestation of mares carrying colts had a tendency to be longer than mares carrying fillies. Maternal parity significantly affected gestational length, with longer gestation for primiparous mares until the third gestation, shorter pregnancies between 4th and 8th gestation, and longer thereafter. Regarding mating period, mares that were mated at the end of the breeding season (January and February) had shorter pregnancies (P < 0.05). These results are of significant clinical and economic relevance for the equine industry, so that the monitoring of gestation and parturition can be performed effectively.

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Background In newborns, exposure to the extrauterine environment with high oxygen tension and sudden pulmonary adaptation leads to an increase in reactive oxygen species (ROS). ROS have several physiological roles, which are essential for neonatal development, however, when unbalanced, these highly unstable molecules can cause cellular destabilisation, compromising vital processes. Objectives To characterise the oxidative status in healthy equine neonates, evaluating an indicator of lipid peroxidation and both enzymatic and nonenzymatic antioxidant systems, during the first week of life. Study design Experimental cohort. Methods Twenty‐four foals were evaluated, with blood collections performed at 5 minutes, 12, 72 and 168 hours after birth. The degree of lipid peroxidation was quantified using Thiobarbituric Acid Reactive Substances (TBARS). Superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzymatic activities, and total, conjugated and unconjugated serum bilirubin levels were also analysed. Comparisons were performed using ANOVA followed by a Tukey's test. Additionally, dependent variables were also evaluated with Pearson's correlation tests. Results Higher GPx activity was observed at 12 and 72 hours when compared to 5 minutes. An increase in TBARS levels was found at 5 minutes after birth, followed by a decrease at 72 hours and stabilisation through subsequent moments until 168 hours after birth. No differences were observed in SOD activity when comparing the four time points. Bilirubin concentrations were lower at 5 minutes after birth and total and unconjugated bilirubin increased at 12 hours and decreased between 72 and 168 hours after birth. Conclusions Lipid peroxidation at birth was high, suggesting an increase in ROS levels relating to physiological events in neonatal adaptation. Antioxidant systems, involving unconjugated bilirubin and GPx, were activated and these biomolecules act concomitantly to reduce ROS levels, thus maintaining oxidative homeostasis. Overall, our results suggest a pro‐oxidant balance during the first 168 hours after birth in equine neonates.

ResumoEsta revisão de literatura propõe levantar os principais fatores que podem influenciar o crescimento intrauterino e o suprimento de nutrientes placentários para o feto, abordando aspectos morfofuncionais relacionados à eficiência placentária, correlacionando-os com aspectos zootécnicos, como raça, pluriparidade e idade das fêmeas gestantes. O objetivo foi estabelecer as interrelações que determinem maior eficiência placentária, propondo um paralelo comparativo entre espécies a fim de ser entendida a eficiência placentária na espécie equina.Palavras-chave: Placenta. Éguas. Gestação. Potros. Parto. AbstractThis review intends to show the main factors that may affect intrauterine growth and the placental's nutrients supply to the fetus, morphofunctional aspects placental efficiency, correlating them with performance indexes, such as breed, age and pluriparious. This study aims to discuss the interrelationships that determine greater placental efficiency, proposing a comparative parallel between various species in order to understand more about the placental efficiency in the equine species.Keywords: Placenta. Mares. Pregnancy. Foals. Parturition. Eficiência placentária na espécie equina:quais fatores podem estar relacionados?Placental efficiency in the equine species: which factors may be related? IntroduçãoEm mamíferos, o maior determinante do crescimento intrauterino é o suprimento de nutrientes placentários para o feto. A capacidade de transferên-cia de nutrientes depende do tamanho, morfologia, fluxo sanguíneo e a eficiência de transporte (FOW-DEN et al., 2006). A placenta sintetiza e metaboliza nutrientes-chave, que somados às influências hormonais atuam na taxa de crescimento do feto (FOW-DEN;FORHEAD, 2004). Problemas em quaisquer desses fatores podem ocasionar mudanças no padrão de crescimento fetal (FOWDEN et al., 2006;JONES;JANSSON, 2007).Funcionalmente, a eficiência placentária pode ser alterada por mudanças na capacidade da placenta suprir os nutrientes ou hormônios para mãe e/ou para o feto. A placenta transporta nutrientes por difusão simples e transporte mediado de maneira passiva ou ativa (SIBLEY et al., 2005). Esses processos dependem das características morfológicas da placenta, como área de superfície, espessura da barreira, densidade capilar e suprimento sanguíneo materno. Os processos de transportes ativos mediados por transportadores específicos são influenciados pela quantidades desses transportadores e da sua atividade e localização, nas membranas placentárias (SIBLEY et al., 2005). A difusão simples e a facilitada, seja ela ativa ou passiva, é afetada pelo gradiente de concentração da materno-fetal da placenta (HAY, 1995).