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Responses of dams versus non-nursing cows to machine milking in terms of milk performance, behaviour and heart rate with and without additional acoustic, olfactory or manual stimulation
•We compared dairy cows which reared their own calf or not while being milked.•The effect of acoustic, olfactory and manual stimuli in the parlour were investigated.•Milk yield, fat content and milk flow was lower in dams: impaired milk ejection.•The stimuli did not influence milk let-down.•Dams had higher vagal activity, but more agitated behaviour in the milking parlour.
There is increasing interest in dam rearing where dairy cows are milked and nurse their calves additionally. One shortcoming in dam rearing is the impaired alveolar milk ejection, which lowers the milk yield obtainable by machine milking. In this study dams and non-nursing dairy cows were compared during milking concerning machine collected milk yield, machine-on time, milk flow characteristics, milk fat content, somatic cell score (SCS), agitation behaviour, heart rate (HR) and heart rate variability (HRV). The effect of acoustic (played-back calf calls), olfactory (hair of the own calf) and manual stimulation (teat massage) on these parameters were examined in the parlour in comparison to routine milking. Between milking times calves of 15 dairy cows had permanent access to the cows’ lying area and were allowed to suckle (‘contact’). ‘Control’ cows were separated from their calf within 12 h after birth (n = 22). All animals were milked twice daily in the same parlour. The experiment was conducted in the second month of lactation. Mixed models were applied. Over all treatments machine collected milk yield (−9.9 kg/milking), fat content (−0.66%) and milk flow characteristics of dams were lower than in ‘control’ animals (all tests: p < 0.0001, effect size r > 0.70). SCS as indicator of udder health did not differ between groups. There was no impact of ‘contact’ on rumination, stepping, kicking, HR and some parameters of HRV (RMSSD, SDNN, HF%) in the parlour. Dams showed a tense head position (p = 0.0007, r = 0.56) and defecated (p = 0.0125, r = 0.50) at more milkings than cows without calf contact. On the other hand, some characteristics of HRV differed between ‘contact’ animals and the ‘control’ (LF%, LF/HF; p < 0.05, r > 0.30), indicating a higher vagal activity in dams. Reason for this may be an in general higher vagal activity due to suckling, which could also result in higher gut motility and therefore a higher defecation frequency. None of the treatments had great impact on the animals. Manual stimulation increased the mean milk flow during the main milking phase. However, this is possibly due to technical differences compared to vibration stimulation without effects on harvested milk. Acoustic stimulation led to lower SCS compared to routine milking, but only in dams (interaction: p = 0.0023). In conclusion, it was not possible to enhance milk let-down in dams with free calf-contact through acoustic, olfactory and manual stimulation.