Effects of hypertonic saline combined with calcium borogluconate compared to calcium borogluconate alone on oxygen saturation, plasma volume and ionised calcium concentration in cows with milk fever

Aims To measure blood ionised calcium (iCa) and lactate (L-lac) concentration, relative plasma volume index (rPV) and oxygen saturation (SpO2), in a small number of dairy cows showing clinical signs of milk fever, and to report the effects of IV administration of calcium borogluconate combined with hypertonic saline solution (HSS), compared with calcium borogluconate alone, on iCa, rPV and SpO2.Methods A convenience sample of 10 Holstein dairy cows from multiple dairy farms showing clinical signs consistent with milk fever and having an iCa concentration ≤ 1.05 mmol/L was enrolled. Blood biochemistry, SpO2, and heart rate measurements were performed, and rPV was calculated with reference to the plasma volume at enrolment as the baseline. Cows were sequentially assigned to treatment groups in alternating order. The combination group (n = 5) received 3 L of 7.2% HSS mixed with 500 mL of 25% calcium borogluconate. The control group (n = 5) received 500 mL of 25% calcium borogluconate alone. Measurements were performed before treatment, immediately after treatment, and 24 hours later.Results Before treatment, the mean iCa concentration in cows with milk fever (n = 10) was 0.59 (SD 0.14; reference range: ≥1.05) mmol/L, the L-lactate concentration was 3.23 (SD 2.02; reference range: 0.31–1.51) mmol/L, and SpO2 was 94.4 (SD 1.8; reference range: 96–100)%. iCa concentrations increased after treatment in both groups. Immediately after treatment, rPV was 141.2 (95% CI = 131.7–150.7)% in the combination group and 120.3 (95% CI = 110.8–129.8)% in the control group, with higher values observed in the combination group. At 24 hours, rPV remained above baseline in both groups, although there was no difference between groups. Immediately after treatment, SpO2 was 99.4 (95% CI = 96.6–102.2)% in the combination group and 90.6 (95% CI = 87.8–93.4)% in the control group, with higher values observed in the combination group. Even at 24 hours after treatment, SpO2 remained increased relative to pre-treatment values in the combination group. In contrast, no increase in SpO2 was observed in the control group throughout the observation period.Conclusions Milk fever was associated with increased blood lactate concentrations and peripheral hypoxaemia, which may suggest circulatory compromise related to hypocalcaemia. Compared with calcium therapy alone, calcium therapy combined with HSS increased rPV immediately after treatment and further improved SpO2.Clinical relevance Adjunctive HSS may provide short-term circulatory support in cows with milk fever receiving standard calcium treatment under commercial farm conditions.