Abstract

The level of the vacuum in machine milking is one of the principal parameters which influence the integrity of the tissues and the milk quality. Many studies have shown that while raising the level of the vacuum increases the speed of milk emission, it can also generate congestion in the teat, formation of oedema, increase in residual milk and in the number of somatic cells. Thus milking should be performed with the lowest possible level of vacuum which is compatible with not excessively prolonging milking time. In Italy the vacuum level is unjustifiably high - on average 42 - 46 kPa- while in other European countries the usually level is 4-5 kPa lower.
In order to define the milking techniques which best satisfy the physiological needs of dairy sheep, we have compared milking performances at a low vacuum level (28 kPa) and at a standard level (42 kPa). The effects of the working conditions were evaluated by analyzing the milk emission curves and the vacuum fluctuations registered in the milkline and in the short milk tube.
Results showed that using a vacuum of 28 kPa increased the latency time, reduced both average and peak milk flow, and increased the average milking time per head by 17%.
The reduction of vacuum did not produce significant variations in vacuum fluctuations in the short milk tube (10.4 kPa at 28 kPa and 9.0 kPa at 42 kPa) and also in the milkline where the vacuum fluctuations were less than 2 kPa.

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