Traumatic and Structural Disorders of the Bovine Udder

The more common causes of primary wounds to the udder are fence wire cuts; hoof treads; abrasions gained in housing or by machine milking, and cows pastured on sandy or stony soils and on abrasive grasses (eg, Bermuda grass and winter crops); insect bites, and suckling by herdmates (mostly causing teeth scratches). Teeth-induced scratches are typically dorsal to ventral, contrasting with chaps which are lateral, along skin folds. Insect bites, usually by bloodsucking flies, mosquitoes, and midges, may be exacerbated by licking of the area or expanded by abrasion by other insects, and often become infected by bacteria.

Superficial wounds to the udder and teats may be cleaned with a suitable antiseptic solution and treated with frequent application of a topical antiseptic. If a teat is cut, adhesive tape may be used to bind the cut to hasten healing and allow milking, if the orifice is not compromised. Wounds involving the teat orifice should be dressed with an antiseptic cream and bandaged after milking. Affected quarters are at high risk of infection, and prophylactic treatment with intramammary antimicrobials is recommended to prevent mastitis.

Lacerations of the large milk vein should be considered an emergency because of the potential for severe hemorrhage; prompt compression and ligation of these lacerations is recommended. Deeper wounds of the udder and teats should be promptly (within 6 hours) cleansed and sutured or stapled under local anesthesia with appropriate sedation and restraint. When the wound involves the teat cistern, it may be necessary to insert a self-retaining teat cannula with removable cap into the teat for the first 24 hours to prevent milk seeping through the wound (which would delay or prevent healing) and to aid in milking. The affected quarter should be infused with an antimicrobial preparation.

Thermal burns are rare but may affect pastured animals in grass fires and with careless use of udder singeing. Subcutaneous hemorrhages affecting the teat, observed initially as petechial patches, are milking-machine induced, principally due to too high a vacuum or impaired pulsation. Continued exposure to the cause leads to coalescence of the hemorrhages and an open sore that is most likely to become secondarily infected by bacteria.

Trauma (often related to inadequate housing) can result in contusions and hematomas of the udder. Hematomas usually appear as soft tissue swellings located cranial to the fore udder or caudodorsal to the hind udder. They may be difficult to differentiate from abscesses. Severe hematomas can result in anemia if not treated. In most instances, hematomas resolve after conservative treatment consisting of pressure wraps and rest. Hematomas should not be incised or drained unless they become infected. Milking should be performed cautiously during the convalescent period. Hematomas that continue to enlarge should be considered an emergency because of the possibility of excessive blood loss and shock.

Teat stenosis is a marked narrowing of the teat orifice or streak canal. It usually results from a contusion or wound that produces swelling or formation of a blood clot or scab or from a mastitis infection (especially in prelactating heifers). Teat obstructions (teat peas) are usually the result of proliferation of granulation tissue after the occurrence of a teat injury. Obstructions are usually recognized when they interfere with milk flow, one quarter remaining all or mostly unmilked. They can be diagnosed initially by careful palpation of the affected gland. They can range from diffuse, tightly adherent lesions to highly mobile discrete lesions that float throughout the teat or gland cistern. Some are due to formation of small masses from butterfat, minerals, and tissue in mammary ducts during the dry period. These can be recognized by intermittent disruptions in milk flow. They may be removed by forced pressure downward on the teat cistern or by use of specialized instruments inserted through the streak canal.

Membranous obstructions in the area of the annular fold at the base of the gland cistern sometimes occur in heifers. Treatment of these obstructions is generally unsuccessful. Complete teat obstruction may result when adhesions fill the teat cistern after severe trauma. In instances of severe injury, milking of the quarter should be permanently discontinued. Complex teat obstructions or obstructions in valuable animals may require diagnostic imaging such as ultrasonography, contrast radiography, or theloscopy (endoscopy). Treatment varies depending on severity. Teat cannulas may be used short-term but are associated with a high risk of mastitis. Serious cases may need referral to specialists for endoscopic surgery. All injuries to, or surgical procedures on, the teat should be handled carefully to prevent infection. Prophylactic antimicrobial treatment is indicated when the teat or teat orifice is involved.

Failure of the suspensory ligaments of the udder (usually the medial suspensory ligament) occurs gradually in some older cows, often related to overengorgement and edema, and leads to a dropping of the udder, resulting in lateral deviation of the teats and making teat cup attachment difficult. Occasionally, acute rupture can occur at or just after parturition. Animals with this condition are at high risk of developing mastitis. There is no successful treatment; supportive trusses generally are not satisfactory. The condition is suspected to have a genetic basis, and these animals should be removed from the milking herd.

The occurrence of pink- or red-tinged milk is common after calving and can be attributed to rupture of small mammary blood vessels. Udder swelling from edema or trauma is a potential underlying cause. Bloody milk is not fit for consumption; submission for sale leads to rejection of the whole supply and penalties. In most cases, it resolves without treatment within 14 days, provided the gland is milked out regularly. Bright red milk from a single quarter is a sign of a larger blood vessel hemorrhage or teat trauma, while dark brown milk results from rupture of a major vein or severe mastitis. Milking should be discontinued until the hemorrhage is controlled. The likely cause of the mastitis should be treated.

Early lactation and high-producing dairy cows may leak milk from the sphincter. This usually occurs when the udder cistern is full or the teat sphincter is inadequate. Risk factors for milk leakage include high-producing heifers which have a relatively small udder cistern compared with mature cows, a high peak milk flow rate (ie, a streak canal that relaxes easily and quickly in response to oxytocin [letdown]), and short teats. Shorter milking intervals (more frequent milking) may help if leakage is a herd phenomenon. Rarely, cows leak milk continuously. These cows usually have sustained a severe teat injury or have an abnormal streak canal. These cows develop mastitis; persistent leakers should be removed from the herd.