SUMMARY
AbstractHeart rate (HR) and heart rate variability (HRV) were investigated in cows (n=32, age: 3.86 years, milk production: 35±2.5 kg, DIM: 150±15) milked in a parallel milking parlour. Geometric parameters of HRV (SD1 and SD2) were calculated using Poincare graphs. HRV indices of resting 1 h after midday milking (reference period) were compared to those measured during the different phases of the evening milking (driving; in the holding pen; udder preparation; milking; after milking in the milking stall). There was no difference between the reference period and the different phases of milking in animal welfare terms. During the reference period SD2 (198.5 ms) was significantly higher (p<0.05) than every other measured period suggesting an increasing parasympathetic tone after milking. This parasympathetic predominance decreased with time of the day (1.5 h after milking). SD2 was significantly affected by parity, by the breeding bull (p<0.01) and by milk production (p<0.05). SD2 was notably higher (102.8 ms) in multiparous cows than in primiparous cows (p<0.017; a=0.005) during resting and milking. Results suggested that a conventional milking process is not really stressful for cows. Primiparous cows were more susceptible of milking process than multiparous ones. SD2 is a good marker of vagus activity and affected by several independent factors.