Photo credit: Ginger Fenton
When it comes to monitoring milk quality on the farm, don’t overlook the obvious tools at your disposal. One of the easiest, least expensive ways that we can detect a milk quality issue is to rely on our senses for gustatory (taste), olfactory (smell), or visual clues if milk is different than normal. A change in the odor, taste, or appearance of milk could reflect a health issue, problems with milking equipment, sanitation, nutrition, or ventilation to name a few.
Visual clues include changes in the color of milk along with clots, flakes, or stringy milk. Including a pre-strip step as part of the milking preparation routine gives you the chance to get a good look at milk from each cow. Minimize the potential of contamination by using a strip cup and refraining from stripping onto bedding material. Another part of the visual inspection includes observing the udder for any signs of clinical mastitis such as redness or inflammation.
Typically, milk does not have much of an odor, so a noticeable odor may indicate the need to investigate the reason for this change. Changes in feed such the inclusion of a new ingredient or switching silage can rapidly be picked up in the odor of milk; although this may not indicate any type of problem rather just denote the change. Similarly, if wild onions, garlic, or other plants are consumed, the milk will have a distinct odor so it may be time for a pasture walk. The cow’s environment can influence the odor of the milk; if ventilation is poor, then a “barny” odor could result. A “cowy” or acetone smell may indicate a metabolic disorder.
Several of the causes of odors in milk also are likely to result in an altered milk taste. As with smell, a feed or forage change can rapidly be reflected in the taste of milk as will the consumption of certain plants including garlic and onions. Milk that tastes soapy, bitter, or like blue cheese is characterized as rancid, which is caused by a breakdown of the milkfat into fatty acids. Factors on the farm that could cause rancidity include air leaks in pipelines or valves, too much agitation of the milk, deficiencies in the cow’s diet, or milk from late lactation cows. Oxidized flavors in milk have been described as tasting like cardboard or a metallic taste. If this off-flavor is detected, a water test to check for minerals including copper, iron, and sulfur may be needed. Other contributors could include feeding forages that are low in vitamin E or feeding high levels of certain fats. An acidic flavor in milk may be due to inadequate cleaning or improper cooling, so a check of cleaning procedures and close monitoring of temperatures would be warranted. A salty flavor may denote milk from cows that are late in lactation or have mastitis.
Some people are able to perceive very subtle changes in odors and flavors, while these changes may not be as noticeable to others. Once milk leaves the farm there are many other reasons that off-flavors or odors can develop that may not be observable until the milk has been stored or processed. Detecting and characterizing an off-flavor or odor of milk on the farm may provide a clue to diagnose the cause of the problem.