Release of oxytocin, prolactin and cortisol in response to extraordinary suckling

The aim of this trial was to clarify whether suckling after several weeks of only machine milking can affect the release of oxytocin, cortisol and prolactin in dairy cows, In total twelve Brown Swiss cows on their first to third lactation were used. Pre-experimental period: all cows were suckled three times daily (9.00, 14.00 and 20.00) and milked twice daily (7.00 and 17.30) in tie housing during the first 5 days postpartum. Afterwards the calves were separated and moved to another building. The cows were moved to loose housing and milked in the dairy parlour within the same stable. Experimental period: after four weeks of only machine milking twice daily, cows were relocated from the herd to the same place as they were housed and milked during their postpartum period. The cows were again suckled on day 3 and 4 after relocation at the same time as above. Oxytocin, cortisol and prolactin levels were evaluated during the first suckling on day 3 (9.00) and during suckling at the same time next day (4th suckling) after relocation. Oxytocin secretion was clearly inhibited in all cows during the first five minutes of suckling with tendency of slow increase during the next minutes of suckling (suckling lasted about 10 min) except for two primiparous cows showing an increase of oxytocin release from the first minute of suckling. The release of oxytocin in response to the 4th suckling significantly increased immediately after start of suckling. Both, cortisol and prolactin significantly increased in response to all sucklings. There were significantly higher prolactin and lower cortisol values during the first suckling as compared with the fourth suckling in primiparous but not in multiparous cows.