Effects of meloxicam administration at birth on blood gas, acid-base status, and predictive value of early cardiac autonomic variables for postnatal adaptation in Holstein-Friesian calves.

BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAIDs) are increasingly administered at birth to neonatal dairy calves, yet the interaction between periparturient meloxicam treatment and calving difficulty on vitality recovery and acid-base normalization has not been prospectively examined. The predictive value of early cardiac autonomic variables for compromised postnatal adaptation also remains unclear. METHODS: In a quasi-randomized, blinded, placebo-controlled trial on 151 Holstein-Friesian calves (NSAID n = 54, Placebo n = 97), a single subcutaneous dose of meloxicam (0.5 mg/kg) or visually identical placebo was administered immediately after delivery. Neonatal vitality was scored at 0, 1, 2, 24, and 48 h using a validated 12-point scale. Venous blood gas and acid-base parameters were analyzed at 0, 1, 2, and 24 h. Heart rate variability (HRV) parameters were calculated from 5-min recording windows at 5 and 30 min postpartum. Linear mixed models (LMM) evaluated vitality and blood gas dynamics. Logistic regression and ROC analysis assessed the predictive value of early HRV and calving difficulty for low vitality at 2 h, including a multivariable model testing the incremental value of HRV beyond calving difficulty. RESULTS: A significant three-way interaction (NSAID × time × calving difficulty) was detected (χ2 = 85.2, P < 0.001; R 2 m = 0.318); NSAID-treated calves had higher vitality at 24 h (P = 0.026) and 48 h (P = 0.017), most pronounced in dystocic calves. Blood gas parameters did not differ at birth; base excess (BE) was modestly lower in NSAID calves at 24 h (4.45 vs. 5.30 mmol/L; P = 0.049), although this was not supported in the repeated-measures model. Ionized calcium was lower in NSAID calves at 0 h and 24 h (P < 0.01). In the Placebo group, dam parity was significantly associated with HRV at 30 min (RMSSD rho = 0.50, P < 0.001). RMSSD at 5 min was the only HRV variable significantly associated with low vitality at 2 h (AUC = 0.635; P = 0.004). Calving difficulty was the strongest predictor (OR = 3.54 per unit; AUC = 0.772; P < 0.001); adding RMSSD to a calving difficulty model improved model fit but did not improve discrimination (ΔAUC = +0.027, 95% CI -0.025 to 0.075; P = 0.300). CONCLUSION: Periparturient meloxicam may modulate neonatal vitality recovery in a calving difficulty-dependent manner without directly reversing perinatal acidosis. Early HRV does not provide clinically useful prediction of compromised postnatal adaptation, and adds no incremental discriminative value beyond calving difficulty; calving difficulty score is the primary determinant. These findings suggest that targeted periparturient NSAID administration may be most justified for calves born after obstetrical assistance, although the quasi-randomized design warrants confirmation in a fully randomized trial.