ICAR Technical Series no. 7 - Nitra Proc.

Bruckmaiertowards the end of lactation (Mayer et al., 1991). A similarly delayed milkejection as in late lactation is observed after short intervals from previousmilking. Intervals shorter than 8 h usually don not occur in conventionalmilking systems but are common in AMS milking. It could be shown thatthe lag time until occurrence of milk ejection in response to teat stimulationis a function of degree of udder filling. Milk ejection was delayed if lessmilk was stored in the udder, independent if due to reduced productionin late lactation or due to short interval from previous milking (Bruckmaierand Hilger, 2001).The lag time until occurrence of milk ejection does not depend of theamount of stored milk per se. Thus, milk ejection occurred after a similarlag time in animals of different production levels at the same stage oflactation (Wellnitz et al., 1999). In this case the degree of filling of theindividual udder was similar, because lower producing udders had lowerstorage capacity. We assume that in partially filled alveoli more contractionof the myoepithelial cells and therefore more time is needed until milk isejected in milk ducts and cistern. Therefore, at low degree of udder filling,i.e. after short intervals from previous milking and in late lactation, milkejection occurs later (Bruckmaier and Hilger, 2001). If no specific prestimulationis applied, cisternal milk is removed during the lag time untiloccurrence of milk ejection. Because cisternal milk yield is particularlylow after short interval from previous milking (Knight et al. 1994) and inlate lactation (Pfeilsticker et al. 1996), i.e. at low udder filling, the negativeeffect of delayed milk ejection is even enhanced by low amounts of cisternalmilk (Bruckmaier and Hilger, 2001). Milking empty teats is theconsequence. Therefore, the duration of teat cleaning in AMS should beadapted to the actual interval from previous milking, under considerationof the lactational stage of each individual cow.Experiments were performed in a conventional parlour to simulate AMSmilking routines (Bruckmaier et al., 2000). Effect of sequential teat cupattachment and delayed teat cup attachment after end of pre-stimulationon OT release and amounts of residual milk was tested. Sequentiallydelayed attachment of teat cups every 20 or every 60 s did not reduce OTrelease. Stimulation of less than four teats has been shown to be sufficientto maintain OT release and alveolar contraction, i.e. sequential attachmentof teat cups does not have negative effects on milk ejection and milkremoval. However, total interruption of teat stimulation (delayed of teatcup attachment) for 2 min between pre-stimulation and start of milkingresulted in transiently decreasing OT concentration and increasingamounts of residual milk.Delayed teatcupattachmentandinterruption ofteatstimulationAfter interruption of teat stimulation the transient decrease ofintramammary pressure was compensated by renewed stimulation(Bruckmaier, 2000). In confirmation of this finding we have demonstratedduring experiments in a multi-box AMS that negative effects on milkICAR Technical Series - No 7195