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Effect of the Short Milk Tube Check Valves on Milking Rate, Milk Yield, and Transfer of Bacteria Among Quarters

Dairy Division, Alberta, Agriculture Lethbridge, Alberta T1K 4X7
Agriculture Canada Research Station, Lethbridge, Alberta T1J 4B1

To determine effect on milk yield, milking time, and rate. Holstein cows were milked using machines equipped with or without short milk tube check valves. In each of three experiments, 16 cows were divided into two groups of 8. Experiments 1 and 2 employed a crossover experimental design; Experiment 3 used a switchback design. Check valves increased 2-min milk yields in all experiments and increased 3-min yields in Experiments 1 and 3, but decreased 3-min yields in Experiment 2. Total milk yield was decreased by check valves in Experiments 1 and 3 but was not affected by check valves in Experiment 2. Milking time was not affected by check valves in Experiments 1 and 3, but decreased in Experiment 2. In two other experiments, three cows were used in a 3 x 3 Latin square to measure transfer of a marker bacteria between teat cups. Bacteria transfer was not different among machines equipped with conventional, check valve, or shielded liners. The check valves functioned during full milk flow, producing hydraulic milking conditions, but they ceased functioning when milk flow declined in the later stages of milking. The check valves were ineffective in increasing milking rate and milk yield and are unlikely to prevent teat end impact.