Specific aspects of milk ejection in robotic milking: a review

Abstract

Milking routines in automatic milking systems (AMS) differ from those in conventional milking. While milking intervals are constant and teat cups are attached simultaneously in conventional milking, in AMS milking intervals are variable and attachment of teat cups can be sequentially delayed. Experiments were performed to test effects of pre-milking teat cleaning, of different milking intervals in different lactational stages, of delayed teat cup attachment and individual teat cup removal on oxytocin release, milk ejection and milk removal. Teat cleaning caused oxytocin release and induced milk ejection. The lag time from start of teat stimulation until milk ejection occurred increased with decreasing milking interval and was longer in late than in early lactation. In addition, milk fat content increased towards the end of lactation and was higher after short than after long intervals from previous milking. Sequentially delayed attachment of teat cups every 20 s or every 60 s did not reduce oxytocin release. However, total interruption of teat stimulation for 2 min between pre-stimulation and start of milking resulted in transiently decreasing oxytocin concentration and increasing amounts of residual milk. The quarters in which teat cups were last removed had non-significantly the smallest amounts of stripping and residual milk. The stimulatory effect of single teat cups during sequentially delayed attachment is sufficient to maintain adequate oxytocin release and maximum milk ejection.