Effect of a low vacuum level on vacuum stability and milking parlor performance for sheep

In line with the current interest in animal welfare in animal husbandry, this study of two groups of 24 sheep
compares milking performances at a low vacuum level (28 kPa) and at a standard level (42 kPa) that is normally used for
sheep. The two working vacuum levels were tested with three different combinations of pulsator rate and pulsator ratio. Each
of the experiments lasted 21 days, of which 11 were for adaptation and 10 were for collecting data. The milking machine used
was a low line with 24 stalls, 12 milking units controlled by two operators, a milk line 74 mm in diameter, and a cluster with
a total mass of 490 g. The measurements performed were the dynamics of the vacuum level in the short milk tube and the milk
line during milking, and the time duration for each individual milking. There were no significant differences in fluctuations
in vacuum in either the short tube or the milk line at the two vacuum levels used. By contrast, there was a significant increase
in vacuum fluctuations in the short milk tube when the pulsator ratio changed from 50% to 60%. The milk flow time for each
sheep increased on average by 17% with low vacuum, while the throughput of the system was reduced by some 4%, from 333
to 321 sheep/h.