Is milk sterile as it drawn from the cow?

Answer 1

Yes, Milk SHOULD be sterile when it is still in the udder, just like urine should be sterile when it's still in the bladder. A healthy udder does not have bacteria in it, so is sterile. In this case the bacteria is picked up in the distal teat canal, and the outside of the teat.

When the udder becomes infected with bacteria (a disease process called mastitis), the milk is no longer sterile. This is when the cow has mastitis, where bacteria have entered the udder and infected the mammary tissue. Most bacteria in a healthy, non-mastitis-infected cow that does affect the milk are found in the teat canal and enter the milk when the milk is excreted through the teats.

Answer 2

No. While when formed in a healthy cow udder of the cow, milk is sterile, if the cow is unhealthy (eg it has TB) the muikl can be contaminated.

Also milk is contaminated by naturally occurring bacteria inhabiting the udder of the cow and is not sterile when it leaves the udder.

While these bacteria may not be harmful to humans, milk is commonly contaminated by other potentially harmful microorganisms originating from many sources.

This is why governments require milk sold to customers to be pasteurized.