• Effects of the design of a milking unit on vacuum variations during simulated milking

      O'Callaghan, Edmond J (Teagasc (Agriculture and Food Development Authority), Ireland, 2004)
      The vacuum variations at the apex of an artificial teat during simulated milking were measured in a factorial-design laboratory test involving six cluster types, two internal diameters (13.5 mm and 16 mm) of long milk tube (LMT), three water flow rates (4, 6 and 8 l/min), simultaneous (4 × 0) and alternate (2 × 2) pulsation patterns and three pulsator ratios (60, 64, and 68%). Four of the six clusters were fitted with wide-bore tapered liners and represented all combinations of two claw volumes (150 or 420 ml) and two short-milk-tube bores (8.5 mm and 13.5 mm). Two clusters were fitted with narrow-bore liners (22 and 25 mm) that had large-bore short milk tubes and large claw volumes. The vacuum variations were expressed as mean vacuum at the teat-end during the b-phase of pulsation (TVB), mean vacuum at the teat end measured over complete pulsation cycles (TV), minimum vacuum measured over complete pulsation cycles (TVM) and amplitude of vacuum fluctuation measured over complete pulsation cycles (TVF). The highest level of TVB was recorded with wide-bore tapered liners. For a milking unit fitted with a wide-bore tapered liner TVF was reduced and TVM increased by increasing either the bore of the short milk tube or the volume of the claw. When the bore of the LMT was increased TVB, TV and TVF increased. Simultaneous pulsation gave higher TVB (P < 0.001) and higher TVF (P < 0.001) than alternate pulsation for all cluster types. The overall effects of altering pulsator ratio were significant but small in practical terms. There were significant interactions between cluster type and water flow rate and pulsation pattern for TVB, TV, TVM and TVF.
    • Note on a portable simulator for analysis of milking machine porformance

      O'Callaghan, Edmond J (Teagasc (Agriculture and Food Development Authority), Ireland, 2004)
      A portable flow simulator was developed for recording vacuum variations in commercial milking machine clusters. The cluster in the milking unit under evaluation was mounted on the frame of the simulator and the flow of water through each liner was regulated by separate flow meters. By placing an artificial teat into the liners the flow characteristics during actual milking were simulated. Measurement vacuum sensors were mounted in the claw, in one artificial teat, in the pulsation chamber and in the milk pipeline. Analog and digital outputs were recorded. The system was validated by comparing the outputs with those obtained with a laboratory flow simulator and with recordings taken during cow milking. The recordings with the portable simulator and the laboratory simulator were identical; the profiles of the analogue signals obtained with the portable simulator and from cow milking were similar. The portable flow simulator will allow recording of vacuum variations in commercial milking machines during simulated or actual milking.
    • A note on the effects of test-end vacuum on milking characteristics

      O'Callaghan, Edmond J; Gleeson, David E; European Union (Teagasc (Agriculture and Food Development Authority), Ireland, 2004)
      The magnitude of vacuum applied to the teat end can have a major effect on milking characteristics. While milking vacuum is usually measured in the milk pipeline, the teat-end vacuum during milk flow depends on the configuration of the milking unit. The objective was to establish the effect of teat-end vacuum, recorded during flow simulation, on actual milking time, milk yield, and both mean and peak milk-flow rates. Four configurations of milking units were set up to give vacuum levels of 35, 38, 40 and 42 kPa at the apex of an artificial teat during simulated milking. The experiment involved a latin square design with four groups of Friesian cows (14/group), four 2-day periods and four treatments (vacuum level). Altering the vacuum level had no significant effect on milk yield. There were no differences in milking characteristics between vacuum levels of 38 and 40 kPa. A vacuum level of 42 kPa gave a shorter milking time (P < 0.001), higher average milk-flow rate (P < 0.01) and higher peak milk-flow rate (P < 0.001) than the three lower vacuum levels. Milking time was significantly longer (P < 0.001) and peak milk-flow rate lower (P < 0.001) with a vacuum of 35 kPa compared to other vacuum levels.