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 m ilking on the oxytocin (OT) secretion and milk yield was studied. Twelve Br own Swiss cows in their fifth week of lactation were used. Animals were rel ocated immediately before the evening milking within the same stable from l oose housing and milking in the parlour to tie stalls where they were milke d. 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 milkings after relocation (first and second milkin g). Blood was collected during the first and second evening milking after r elocation. Relocation of cows significantly reduced milk yield, and this re duction was significantly recovered during the second evening milking. The OT concentrations significantly increased during the second milking compare d with the first milking after relocation. Positive correlation between inc reased OT concentration and increased milk yield from first to second eveni ng milking it (r = 0.532) was calculated. In conclusion, the lower milk yie ld after the change of housing and milking conditions can be concomitant wi th disturbed OT release but a mechanism responsible for decreased milk yiel d is unclear.