Seasonal and maternal effects on acid-base, l-lactate, electrolyte, and hematological status of 205 dairy calves born to eutocic dams

ABSTRACT In this study, we used linear mixed models to determine the effects of season, time of sampling relative to birth (factors), duration of the delivery process, duration of maternal grooming, calf body weight (BW) at birth, and time of day (covariates) on values of venous blood gas, acid-base and electrolyte parameters, and l-lactate concentrations in dairy calves born to eutocic dams in summer (SUM, n=101) and winter (WIN, n=104). Neonatal vitality was assessed at 0, 1, and 24 h after delivery in a linear scoring system using muscle tone, erection of the head, muscle reflexes, heart rate, and sucking drive as criteria. Simultaneously with vitality scoring, venous blood samples were collected by jugular venipuncture. Blood was tested for pH, partial pressure of CO 2 (pCO 2 ; mmHg) and oxygen (pO 2 ; mmHg), l-lactate (mmol/L), hemoglobin (Hb; g/L), ionized calcium (Ca 2+ ; mmol/L), sodium (Na + ; mmol/L), potassium (K + ; mmol/L) and chloride (Cl – ; mmol/L). Bicarbonate (HCO 3 – ; mmol/L), base excess (BE; mmol/L), total carbon dioxide (TCO 2 ; mmol/L), and anion gap (mmol/L) were calculated. Electrolyte parameters were affected by none of the factors or covariates. Time of day at birth did not affect any of the parameters of interest. Vitality score tended to increase over time and it showed higher values in WIN calves than in SUM calves. Concentrations of HCO 3 – , BE, and l-lactate indicated a higher degree of metabolic acidosis in SUM calves; however, pH was not affected by season. Concentrations of Hb were higher in SUM calves than in WIN calves; however, covariates did not affect Hb concentrations. Blood pH, concentrations of pO 2 , HCO 3 – , and BE decreased, whereas l-lactate concentrations and values of pCO 2 , TCO 2 , and anion gap increased with longer duration of delivery. A shift in acid-base balance was also linked to BW of the calf at birth, with lower values of blood pH, HCO 3 – , and BE in calves with higher BW compared with those with lower BW at birth, whereas TCO 2 and l-lactate concentrations increased with higher calf BW at birth. Values of pO 2 increased and pCO 2 decreased with longer duration of maternal grooming. Blood pH, HCO 3 – , and BE increased, whereas l-lactate concentrations and anion gap decreased with longer duration of licking the calf. Our results indicate that prolonged delivery can impair acid-base status and can cause slight lactic acidosis, even in calves born from spontaneous or eutocic calvings, and that high BW at birth predisposes calves to acidosis. The positive effect of maternal grooming on neonatal acid-base status should be considered in parturition management. Season, duration of the delivery process, calf BW at birth, and duration of maternal grooming are recommended for consideration in future studies on blood gas and acid-base parameters in dairy calves in the immediate neonatal period.