Marcela Gonçalves Meirelles

Influence of Maternal Age and Parity on Placental Structure and Foal Characteristics From Birth up to 2 Years of Age

ABSTRACT The foals weight and height at birth are regarded as important parameters for the equestrian sports industry. Moreover, scientific studies indicate that maternal environment can influence postnatal genetic potential of foals. The purpose of this study was to evaluate the influence of maternal age and parity on placental efficiency and size of the newborn foal using stereological analysis tools of the terms allantochorion. Furthermore, the influence of maternal age and parity on weight, height, and girth circumference of the offspring from birth until 2 years of age was investigated. Forty pregnant mares were categorized according to age: 4–8 years (n = 15); 9–12 years (n = 15); ≥13 years (n = 10) and parity: nulliparous (n = 12), 1–3 parities (n = 18); ≥4 parities (n = 10). Parturition was monitored and the allantochorion membranes were collected after delivery. The stereological analysis determined the volumetric composition of the different compartments of the placenta along with the area of fetomaternal contact surface. It was observed that maternal age and parity significantly increased the development of the microcotyledons and total villi surface density, as well as the vascularization and tissue composition of different regions of the placenta, which contributes to fetomaternal contact. We also found a significant relationship between maternal age and parity on the size of the neonate foals but not after the first year of age, possibly because environmental and genetic factors contribute to postnatal growth. HIGHLIGHTSMaternal age and parity influence placental characteristics and fetomaternal contact.Mares age and parity influence neonatal size at birth.After the first year, differences in height, weight, and girth circumference disappear.

Factors affecting gestational length in the Mangalarga Paulista breed

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.