Milking Procedures Affect Milk Quality

Rory Lewandowski, Extension Educator, Wayne County, Ohio State University Extension

            In today’s competitive milk market, the production of high quality milk is a must. An article by Jeffrey Reneau from the University of Minnesota entitled “Milk Quality in the 21st Century” says that high quality raw milk is free of undesirable flavors, chemicals, or antibiotic residues; is low in somatic cells and bacteria; and contains a minimum of 3.5% butterfat, 3.1% protein, and 4.8% lactose. One important aspect of producing quality milk that has a low somatic cell count and bacteria level is the establishment of a consistent milking procedure that emphasizes udder and teat hygiene, along with cow care. Managers should periodically review milking procedures with milkers. Observe milking routines and evaluate milkers to insure that procedures are followed correctly and consistently.

Pre-milking preparation begins as cows enter the parlor. Cows should enter calmly. Milkers need to work in a calm manner as well. I have heard this described as “working at cow speed”.  Milkers should wear nitrile gloves as they work through the cow preparation and milking procedures. 

Dr. Pamela Ruegg, formerly at the University of Wisconsin and currently chair of the Department of Animal Science at Michigan State University, and Dr. Jeffrey Reneau at the University of Minnesota are big proponents of implementing standardized milking procedures on the farm and training all milkers to follow those procedures during the milking routine. Cows are creatures of habit; they like routines. They do not favor change or surprises. Dr. Reneau cites a year-long Denmark study that found when cows were milked in a standardized routine where pre-milking cow prep and prep-lag time were optimized, 5.5% more milk was produced compared to cows milked in a non-standardized minimal milking routine. Dr. Ruegg has identified seven habits of successful milking routines that she advises milkers to practice; the publication is available on-line at In this article, I’ll focus on Dr. Ruegg’s advice concerning cow preparation and milking procedures.

Cow preparation involves cleaning the udders and teats and stimulating milk let down. The goal here is to start with cows that are clean upon entry into the milking parlor so that milkers are only doing a dry wipe of the udders and teats to remove bedding material, such as sand or straw, before proceeding to a pre-dip and forestripping. The purpose of pre-dipping is to disinfect the teat ends and control environmental pathogens. Consistent and complete coverage of the teat end with a disinfectant dip can reduce teat surface bacteria by 75% and reduce the incidence of mastitis. Effective disinfection requires 30 seconds of contact time before wiping off the dip.

Milk let down is a response to a release of oxytocin from the pituitary gland, along with stimulation of the nervous system and muscles in the udder.  Typically, 10 to 20 seconds of manual stimulation will provide optimal milk let down and result in higher milk yield, milk flow rate, and reduced milking unit on time as compared to no stimulation.  One excellent way to provide this manual stimulation is to forestrip the udder, removing 3 to 4 streams of milk from each teat.  In addition to providing stimulus for milk let down, it allows milkers to perform a check for any visual symptoms of abnormal milk that should not go into the bulk tank.  Research done by Dr. Ruegg on Wisconsin dairy farms demonstrated that milkers might either pre-dip then forestrip or forestrip and then pre-dip.  The order does not matter as long as both are done and the pre-dip is on the teat for 30 seconds.

Dry teats with an individual cloth or paper towel after disinfecting. This is a critical step because wet teats allow skin bacteria easy access up the teat canal and wet teats reduce the friction between the teat and milk inflation, resulting in more slips and greater opportunity for environmental pathogens to enter the system.

The next step in the milking routine is to attach the milking unit. The time from initial contact with teat surfaces until milker unit attachment is termed prep lag time. The prep lag time goal is 60 to 120 seconds. This time frame synchs milker attachment with peak oxytocin concentrations in blood, resulting in milk flow immediately after milking unit attachment. Properly align and center the milking unit under the udder to minimize liner slips and facilitate milking unit removal. I think it is worth mentioning at this point that keeping cows calm and contented throughout the prep and milking time is a key factor in the release of oxytocin and the subsequent milk let down and milk out. If at any point in this process the cow becomes upset, startled, or scared, this triggers the release of adrenalin, which trumps oxytocin and stops the milk let down process.

Shut off the vacuum and remove milking units when milking is completed. Automatic take offs are set to shut off the vacuum when milk flow rate falls below a pre-set level (typically between 0.5 to 1.0 lb/minute) and then remove the milking unit after a short delay. Cows will normally have 2 to 4 cups of milk remaining in the udder upon completion of milking. Do not over milk. This can cause teat end damage and result in mastitis. 

After milking unit removal, dip at least the lower one-third of each teat with an antiseptic product. As part of a mastitis prevention program, ensure that cows remain standing for at least 30 minutes after milking to allow the teat sphincter muscle to fully close.

Like all routines, over time, attention to detail can slip and variation can creep in. Periodic review of milking procedures and the milking routine can aid in maintaining quality milk production.