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

The aim of this trial was to clarify whether suckling after several weeks o f only machine milking can affect the release of oxytocin, cortisol and pro lactin in dairy cows, In total twelve Brown Swiss cows on their first to th ird lactation were used. Pre-experimental period: all cows were suckled thr ee 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 calve s were separated and moved to another building. The cows were moved to loos e housing and milked in the dairy parlour within the same stable. Experimen tal 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 d uring their postpartum period. The cows were again suckled on day 3 and 4 a fter 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. Oxytoc in secretion was clearly inhibited in all cows during the first five minute s of suckling with tendency of slow increase during the next minutes of suc kling (suckling lasted about 10 min) except for two primiparous cows showin g an increase of oxytocin release from the first minute of suckling. The re lease of oxytocin in response to the 4th suckling significantly increased i mmediately after start of suckling. Both, cortisol and prolactin significan tly 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.