Avaliação de métodos de predição de parto e de características clínicas, laboratoriais e comportamentais de potros Mangalarga Marchador durante a primeira semana de vida

Abstract

During the neonatal period, several adaptations to the external environment are necessary. At this age, routine clinical evaluations are performed to monitor the organic development of foals and their clinical abnormalities. The aim of the present study was to evaluate clinical and behavioral characteristics of Mangalarga Marchador (MM) neonates, as well as to individualize clinical parameters that will serve as a reference for the breed. To assess the proximity of parturition in MM mares, the pH and concentration of Calcium (Ca2+), Magnesium (Mg2+), Chloride (Cl-), Sodium (Na+) and Potassium (K+) of the mammary gland secretion were analyzed. The pH, measured by reagent strip and pH meter, and the electrolytes Ca2+, Mg2+ and Cl- changed significantly in the last 10 days before parturition (p<0.05). Within 24 hours to parturition, the pH decreased significantly to 6.67±0.42 (pH meter) and 6.23±0.53 (reagent strips) and Ca2+ (12.6±5.8mmol/L) and Mg2+ (10.93 ±3.66mmol/L) increased (p<0.0001). Chloride significantly decreased 8 days before parturition (p<0.0001) but remained stable until foaling. Those findings are important to predict parturition in the breed. At birth, healthy foals had an average weight of 32.24±3.85kg and the placental weight corresponded to 10.49±1.03% of the foal's weight. There was a positive correlation between foal weight/placenta weight (r=0.56, p=0.031). When behavior was assessed, the mean time for newborns to assumed sternal position was 10.76±2.77 minutes, to stand was 26.07±7.96 minutes, the first feeding occurred at 47.23±10.47 minutes and elimination of the meconium occurred with 59.0±12.97 minutes. All behaviors were within the reference interval for the species. A significant weight gain was identified during the first week of life (average of 1.41 kg/day). The body temperature stabilized when the foals were 12-hours old. Heart and respiratory rate reached the lowest mean values at one week of age (p<0.05). When hematological and biochemical parameters were evaluated during the first week of life, significant changes were observed on erythrocyte count, hematocrit, platelets, VCM, RDW, leukocytes, nitrogenous urea, creatinine, PPT, globulins, bilirubin, GGT, AST, glycemia, lactate, fibrinogen and electrolytes (Ca2+, Mg2+, Cl-, Na+ and K+) (p< 0.05). The observed changes reflect adaptations to extrauterine life, as well as the development of different organs and systems. The colostrum ingested by the foals had a good quality ((x ) ̅26.8±4.4% BRIX degrees) and the mean serum IgG at 24 hours of life was 3,589.25±878.48 mg/dL. There was no correlation between BRIX analysis in the colostrum and the serum IgG concentration in the foal’s serum (p>0.05). The total serum IgG, assessed by radial immunodiffusion (“gold test”) had a moderate to strong positive correlation with the concentration of total plasmatic proteins, analyzed by biochemical analyzer (r=0.69, p<0.001), refractometry (r =0.82, p<0.001) and globulins (r=0.66, p<0.001). The adequate transfer of immunity observed reflects the ingestion and adequate absorption of good quality colostrum. PPT is an alternative to evaluate adequate transfer of immunity, based on its strong correlation with IgG values.