3 April 2023

5 minute read

By: Carly Becker

Have you ever touched an udder that is so swollen your finger imprint takes a few seconds to disappear, like touching a memory foam mattress? The skin on the udder being so tight is what causes the pitting (depression) from the finger pressure on the udder. This is a noninfectious metabolic disorder known as udder edema. 

Udder edema is most common immediately before or immediately after calving in high-producing dairy cows, especially in first-calf heifers. When walking through dairy barns, it is common to see at least one or two cows with udder edema. In Holstein dairy operations, 66% of cows have udder edema at least once in their lifetime (Okkema and Grandin, 2021). This disorder causes tenderness in the udder and teats leading to cows exhibiting behavior that indicates pain and discomfort.

What is udder edema and how does it occur?

Udder edema is a build-up of lymphatic fluid in and around the interstitial spaces of the udder (Kojouri et al., 2015). During pregnancy, the pressure from the fetus in the pelvic area hinders blood and lymphatic fluid circulation resulting in fluid build-up. 

Feeding a close-up dry ration that is high in salt can contribute to more severe cases of udder edema. A swollen udder makes attaching the milking unit difficult and milk flow may be disrupted, leading to teat condition problems (Hillerton, 2022). This disorder is not caused by mastitis, but cows with udder edema do have an increased risk for development of mastitis. 

First-calf heifers are more susceptible to developing udder edema because even though the mammary system is already in place, significant development occurs during the last stage of gestation. The increased demand of blood for the continued development of the mammary system is a precursor to udder edema. The milk vein (subcutaneous abdominal vein) on mature cows allows for proper blood flow, whereas the milk vein is not yet present in heifers. 

Genetics also play a role in the predisposition to developing udder edema. Cows with a high milk yield have an increased genetic potential to develop udder edema compared to cows with lower milk production (Van Dorp et al., 1998).

Factors that contribute to a greater risk of developing udder edema include age at first calving, gestation length, genetics, nutritional management, over conditioning, and lack of exercise in the close-up prepartum period (Hillerton, 2022). A greater age at first calving (AFC) and increased gestation length have been correlated with an increased risk of developing udder edema (Malven et al., 1983). This could be due to these animals being over conditioned at the time of calving. 

One researcher has reported that Jersey heifers are more susceptible to develop udder edema compared to Holstein heifers (Nestor et al., 1988). This has been attributed to the smaller frame size of Jersey's compared to Holstein's. This area of research has not been thoroughly studied since the 1980s, therefore, more current research is necessary to validate these results. Udder depth and udder support are conformation traits that have been correlated with an increased occurrence of udder edema. 

Cows with udder edema experience deterioration of udder support structures that lead to low-hanging udders (Dentine and McDaniel, 1984). With low hanging, pendulous udders, cows are going to have a greater risk of injuring a teat and more likely to pick-up environmental mastitis-causing pathogens on the teat end opening from stall surfaces or walkways.

Why should we be concerned?

Udder edema usually resolves within a week after calving but researchers have reported that this metabolic disorder can have negative effects on the productive life, the health and wellness, and longevity of dairy cows. Cows experiencing udder edema exhibit similar behaviors as cows with mastitis, such as spending less total time lying and greater kicking behavior when being milked. These behaviors indicate that cows with udder edema may be experiencing pain due to tenderness of the teats and swelling of udder tissues.

Another concern that comes along with udder edema is the increased risk for udder cleft dermatitis. This is also referred to as "udder rot" - a skin lesion that appears in areas of tightly adjacent skin. For example, if there is severe swelling of the udder friction in the pit between the leg and udder can lead to chafing and dermatitis. This area is sometimes hard to see and can be difficult to keep clean and dry. These sores typically have pus present with inflamed skin, a strong "infection" odor, and will bleed easily. Udder cleft dermatitis is more commonly seen in 2+ lactation cows and is associated with a greater risk for clinical mastitis (Persson Waller et al., 2014).

Prevention is key

Udder edema will always be a challenge for producers but reducing the number of animals that experience udder edema is the goal. This is a list of management areas to focus on when aiming to reduce the prevalence of udder edema:

• Provide a separate diet for late gestation heifers to monitor their anionic salt intake
• Include antioxidants such as vitamin E, vitamin C, carotenoids, and flavonoids in the diet
• Select for bulls that are shown to improve udder cleft, udder depth, and udder balance
• Manage body condition- the goal is to maintain body condition in the dry period
• Aim for an age at first calving of 22 to 24 months 

Headline image: cow with udder edema. Photo courtesy of Carly Becker, Penn State Extension