Various frequencies have been tried:
<a href="http:&#x2F;&#x2F;wdmc.org&#x2F;1997&#x2F;MilkingFrequency.pdf" rel="nofollow">http:&#x2F;&#x2F;wdmc.org&#x2F;1997&#x2F;MilkingFrequency.pdf</a><p>but technology has also advanced to the point
where each cow can choose its own frequency:
<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Automatic_milking#Advantages" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Automatic_milking#Advantages</a>