Estudo da morfometria do alantocórion e cordão umbilical de éguas Crioulas

Abstract

The placenta is characterized as a transitional organ, formed by tissues of maternal and fetal origin, with the function of transporting nutritional substances from the maternal organism to the fetus, as well as promoting metabolic exchanges and performing endocrine functions, being responsible for the synthesis, secretion and absorption of a series of substances, including hormones, growth factors, enzymes, proteins and carbohydrates, all essential for the development of the fetus. The breeding of Criollo horses is widespread in the Americas. Information from 2016 shows that Brazil has a total of 379,957 animals, with 94.2% of this population found in the south of Brazil, in the states of Rio Grande do Sul, Santa Catarina and Paraná, with the largest number of specimens in Rio Grande do Sul. Considering the great importance of the breed and the scarcity of specific information on placentation, this work aims to characterize the placenta and umbilical cord of Criollo mares in the postpartum period, considering macroscopic evaluation, histological, morphometric and stereological. Thus, three articles were written. Article 1: "Anato morphofunctional characteristics of the allantochorion of healthy Criollo mares and their relationship with maternal and neonatal biometrics". During 4 breeding seasons, a total of 39 placentas were collected from Criollo mares. The following evaluations were carried out to obtain variables and indices: Maternal and fetal biometry; macroscopic evaluation and obtaining morphometric measurements of the placenta; collection of fragments; histopathologic evaluation and stereologic evaluation. Therefore, the objective of the experiment is to determine the morphological, histological and stereological characteristics of the full-term placenta and umbilical cord of Criollo mares foaled in southern Brazil. A model of linear measurements was developed and the microcotyledonary and vascular histomorphometric averages for this allantochorionic pattern were described. Correlations between histomorphometry and placental expulsion time, foal weight, and gestational age of the animals were established, demonstrating their influence. The average length of the umbilical cord was 54 cm, with a common type I vascular pattern and an attachment pattern on the dorsal allantoic surface. Article 2: "Histomorphometric evaluation of chorioallantois in the equine species using digital image analysis" 12 mares of the Creole breed with a mean age of 8.4 ± 4 years were followed, with eutopic birth and birth of a single healthy foal. The placentas were delivered in 25.3 ± 10 minutes and weighed 4.5 ± 0.7 kg. Histologic evaluation revealed characteristic findings of healthy, term placentas in the equine species. For digital evaluation, images were evaluated in RGB colors with the total number of pixels calibrated to μm. Quantification of the microcotyledonary and capillary area was performed using the Color Threshold macro, and the color range was adjusted using the RGB scale. A total of 360 photographs were evaluated. The histomorphometric measurements obtained showed a normal distribution pattern and the homogeneity of the data can be demonstrated by the low values of the dispersion measurements among the mares evaluated. It can be concluded that the use of digital image analysis for the evaluation of microcotyledonary histomorphometry of equine placentas in gestation proved to be a suitable tool for obtaining objective information about this structure. Article 3: "Equine umbilical cord: characteristics during pregnancy and postpartum evaluation", aimed to carry out a review of the characteristics of the umbilical cord during pregnancy in horses, as well as describe the main changes and incidental findings in the evaluation of this together to the placenta and the newborn in the postpartum period, thus adding knowledge and conducting a literature review for the experiments. The present work achieved its objectives by describing the analysis techniques and standard measurements for morphometry and stereology in an unprecedented way for the Criollo horse.