Factors affecting milk ejection and removal during milking and suckling ofdairy cows

The release of oxytocin and milk ejection occurrence in response to teat st imulation are crucial for fast and complete milk removal during milking or suckling. The milk ejection reflex can be disturbed at central or periphera l level under different experimental and practical conditions. The central disturbance results in the lack or insufficient ejection of the alveolar mi lk into the cistern due to inhibited oxytocin release from pituitary into t he blood circulation. The important role in the pathophysiological regulati on of the inhibited release of oxytocin is played by an opioid system. Endo genous opioids have suppressive effects on oxytocin release under the norma l conditions of milk removal. However under the conditions of disturbed mil k ejection their role in dairy cows was not confirmed. Other possible mecha nisms involved in the central inhibition of oxytocin release are discussed. Tn dairy cows as compared with rats the mechanisms involved in the regulat ion of oxytocin release at the central level remain unclear. The central in hibition of oxytocin release has often been observed in dairy practice duri ng milking of primiparous cows alter parturition, suckling by alien calf, c alf removal before milking, milking of cows in the presence of own calf, re location and milking in an unknown milking place. If sufficient released ox ytocin cannot induce the transfer of milk from alveoli to cistern, peripher al mechanisms are involved. Peripheral mechanisms are related to the increa sed levels of catecholamines and/or activation sympathetic nervous system a t the udder level. In conclusion, the release of oxytocin and milk ejection efficiency can be very easily suppressed by many factors. The effect of mi lking conditions on regulation of milk ejection has to be considered. Thus the physiological requirements of dairy cows have to be respected.