Electrocardiographic aspects of singleton pregnancy and neonatal period in American Miniature horse breed

ABSTRACT

Background: During pregnancy, cardiovascular adaptations occur in order to meet maternal demands and adequate supportfor fetal development, but they are still unclear in the equine species, especially in the American Miniature horse breed.The main hemodynamic changes that occur during pregnancy are increased heart rate, cardiac output, and blood volume.It is necessary to use the reference values for the miniature breeds, in addition to the age range and reproductive condition,so the objective of this study was to evaluate the effect of pregnancy on electrocardiographic (ECG) parameters in maresand also of age in newborns foals of American Miniature horse breed.Materials, Methods & Results: Ten American Miniature Horse mares, between 7 and 19 years old (12.14 ± 4.05 years),116.85 ± 24.09 kg of body weight were used in the experiment. All these mares were pluriparous, with 5.9 ± 3.5 of births,minimum of 2, and maximum of 12 foaling times. They were maintained in common social group in an indoor house stablewith straw bed, with access to an outdoor paddock for several h per day. Twice a day they were fed with hay. Mineral supplements and water were available ad libitum. The ECG were obtained in 10 pregnant mares and in 10 neonates. All femaleswere examined at a representative time of each trimester of pregnancy, at 30, 210, 300 days before and 21 days after delivery.Neonates were examined on different times first 24 h after delivery, weekly on the 7th, 14th, 21st, 28th and 35th days of age.The ECG parameters considered were the heart rate and rhythm, duration and intervals (P, PR, QRS, QT, T) and amplitude(P, R, S, T) of ECG waves. The mean of pregnancy duration was 319.4 ± 4.97 days. Heart Rate (HR) varied between 51 to59 bpm during pregnancy and 56 bpm on the 21st day after delivery. Comparing the clinical parameters of pregnant mares,non-pregnant mares and foal a difference was found for HR, Respiration Rate (RR) and...