Mechanics of the teat and teatcup liner during milking: information from radiographs

Abstract

SummaryFor radiographic studies of the teat and teatcup liner during milking, quarters were infused with a suspension of propyliodone in milk. Simultaneous recordings of vacuum within the liner, in the mouthpiece chamber and in the pulsation chamber, and recordings of liner-wall movement, were made in conjunction with the radiographs.The studies indicated that the sudden decline in milk flow-rate at the end of the period of peak flow-rate from each quarter, and the concurrent changes in the appearance and position of the teat in the liner, result from a fall in teat sinus pressure. This fall in pressure follows the partial closing of the milk passageway between the teat and udder sinuses. The changes initiating the closing of this connexion seem to occur above the teatcup and are associated with the declining amount of milk in the udder.The teat is elongated by 33–50% as it enters the liner and further stretching of the skin of the teat throughout milking is negligible. Thus, increase in the depth of penetration of the teat into the liner is due to more of the teat entering the top of the liner.The force exerted on the teat by the closed liner, which is greatest near the end of the teat, usually appears to increase near the end of milking. The force acting against the inner surface of the open liner barrel is greatest during the peak flow-rate period and it appears to be fairly uniform over most of the area of contact.

Teat length and penetration into teatcup during milking in Norwegian Red Cattle

“…This was most probably due to the occurrence of less creeping of the teacups on long teats, because long teats have large contact area with the barrel of the liner, and thus were more stable both against creeping and falling off. This is consistent with the model of Mein et al (1973).…”

“…Available data on the elasticity of teat tissue show wide variation. Mein et al (1973) found that the teats stretched 33-50%, while Williams & Mein (1982) found a 70% stretching. In any event, stretching of teat tissue constituted so great a part of the total elongation that the existence of a correlation between elongation and initial teat length appeared likely.…”

“…960016-01. When mounted in the shell, this type of liner has a total length of 160 mm from its mouthpiece to the base of the shell and the effective length, as defined by Mein et al (1973), is about 130 mm.…”

Effect of variable traction on the teatcup during machine milking of ewes with or without hand stripping

“…The 9% increase in the machine milk fraction could be due to the traction exerted on the teats, which allowed the communication between gland and teat cisterns to remain open for a longer period of time (Mein et al, 1973); this would also explain why the milking time increased by 12 s. Although both machine and hand strippings decreased with the traction system, it is important to note that the first fraction did so to a greater extent (-51 and -30 ml for machine and hand stripping, respectively). Furthermore, the higher fat content of the hand stripping fraction also confirms that, after removal of the teatcups, the traction system left less milk in the udder than the control system.…”

“…En outre, ce système accroît le temps de traite (12 s; p < 0, 001). Quand la repasse manuelle est supprimée (période 2), le système de traction a tendance à améliorer le fractionnement par rapport au système témoin, mais la production totale du lait et des matières grasses varie très peu (+l,7et+5,9%, respectivement; p > 0,05 (Mein et al, 1973;. In ewes, machine stripping is normally applied by vigorously massaging the udder for 6-10 s just before the teatcups are removed (Labussibre, 1983).…”