The oxytocin secretion and milk letdown during milking immediately after the change of milking and housing conditions

The effect of relocation to known surroundings immediately before machine milking on the oxytocin (OT) secretion and milk yield was studied. Twelve Brown Swiss cows in their fifth week of lactation were used. Animals were relocated immediately before the evening milking within the same stable from loose housing and milking in the parlour to tie stalls where they were milked. All cows had previous experience with this type of housing. Milk yields were recorded two evenings before relocation (control) and during the first two consecutive evening milking after relocation (first and second milking). Blood was collected during the first and second evening milking after relocation. Relocation of cows significantly reduced milk yield, and this reduction was significantly recovered during the second evening milking. The OT concentrations significantly increased during the second milking compared with the first milking after relocation. Positive correlation between increased OT concentration and increased milk yield from first to second evening milking (r = 0.532) was calculated. In conclusion, the lower milk yield after the change of housing and milking conditions can be concomitant with disturbed OT release but a mechanism responsible for decreased milk yield is unclear.