Optimal timing of elective caesarean section in Belgian White and Blue breed of cattle: The calf's point of view

The purpose of this study was to evaluate whether the timing of elective caesarean section (ECS) during parturition affects pulmonary and metabolic adaptation to extra-uterine life in healthy Belgian White and Blue (BWB) calves delivered at term. Vaginal palpation was performed and deliveries divided into six categories of timing for ECS: cervix closed (TECS 1) passive and active cervical dilatation (TECS 2 and TECS 3); full cervical dilatation (TECS 4); spontaneous rupture of allantoic (TECS 5) and amniotic (TECS 6) membranes. One hundred and eighteen BWB calves were examined at birth, 5, 15, 30, 45 and 60 min and 2, 3, 6, 12 and 24 h after birth using the following measurements: physical examination (time between birth and sternal recumbency [T-SR]) heart rate (mHR); arterial blood gas analyses (arterial partial pressure in oxygen [PaO2], in carbon dioxide [PaCO2], arterial haemoglobin oxygen saturation [SaO(2)], alveolo-arterial difference in oxygen [AaDO(2)]); pulmonary function tests using the oesophageal balloon catheter technique (respiratory rate [RR], total pulmonary resistance [R-I], dynamic lung compliance [C-Ldyn], tidal volume [V-T] and minute Volume [V-E]; arterial and venous blood acid-base balance analyses (arterial and venous pH [pHa and pHv], bicarbonate concentration [HCO(3)a and HCO(3)v], base excess [BEa and BEv]); rectal temperature (RT); jugular venous blood sampling for, determination of metabolic variables (blood glucose [G], plasma lactate [L], serum cortisol [C], plasma noradrenaline [NA] and adrenaline [A] concentrations); haematological variables (red blood cell count [RBC], total haemoglobin concentration [Hb], Packed Cell Volume [PCV]) and passive immune transfer variables (total serum protein [TP] and beta(2)gammaglobulin [beta(2)gamma] concentrations). TECS significantly (Pless than or equal to0.05) influenced PaO2, SaO(2), AaDO(2), RR, V-T, V-E, C-Ldyn, RT, G, NA, A, RBC, Hb and TP: compared to TECSgreater than or equal to4 calves, TECSless than or equal to3 calves showed lower PaO2, SaO(2), V-T, C-Ldyn, RT, G, NA, A, RBC, Hb and TP and higher AaDO(2), RR, V-E. TECS differences progressively decreased and disappeared between 6 and 12 h after birth in TECS 2 and 3 calves but remained tip to 24 h in TECS 1 calves. Improved postnatal respiratory and metabolic adaptation in TECSgreater than or equal to4 calves were mainly related to differences in exposure to labour and subsequent hormonal surge: catecholamines, particularly A, enabled more effective removal of lung liquid and/or release of surfactant which contribute to better gas exchanges and induced greater energy mobilization to maintain adequate body temperature. It was concluded waiting for full cervical dilatation before performing CS should be encouraged because it promotes postnatal respiratory and metabolic adaptation in full-term BWB calves.