Plasma T3 and T4 concentrations in newborn calves: influence of type of delivery and breed.

AIM OF THE STUDY In the neonatal adaptation to the extra-uterine life, thyroid hormones play an important role in the process of growth, energy metabolism and thermogenesis. Thyroid hormones profiles were described in newborn calves from different breeds (1), while the influence of gender, birth weight and type of delivery is still unclear. The aim of the study was to compare T3 and T4 plasma concentrations in Holstein-Friesian newborn calves born by vaginal delivery and Belgian Blue born by caesarean section. MATERIALS AND METHODS The study was conducted on 12 Holstein-Friesian calves born by vaginal delivery (VD) and on 12 Belgian Blue calves born by caesarean section (CS). Calves gender, body weight and viability were recorded immediately after birth. Blood samples were collected from jugular vein at 10 and 20 minutes (m), at 6 and 24 hours (h) and at 7 and 14 days (d) of age and plasma stored for T3 and T4 analysis by RIA. The ANCOVA for repeated measures test was used to assess the effect of gender and birth weight on T3 and T4 plasma levels profiles within each group. One-way ANOVA was used to evaluate possible differences in T3 and T4 levels between the two groups in each sampling time (p