Other Conditions of the Mammary Gland

UDDER EDEMA. Dairy cattle frequently develop physiologic edema of the udder during the periparturient period, and heifers have increased incidence of this disorder. Physiologic udder edema must be differentiated from pathologic edema, which can accompany mastitis and diseases of other body systems.

In most cases, physiologic edema is of little consequence and resolves spontaneously after parturition. However, treatment is recommended if the udder becomes excessively large and heavy, because this threatens the integrity of the udder sus­pensory apparatus and predisposes to teat injury and mastitis. Severe edema also can hinder ambulation or impair milking or nursing of the teats. If the edematous udder impinges on the skin of the thigh, moist dermatitis and secondary infection may develop, and the skin may slough; this condition is referred to as udder scald.

The mechanism(s) of physiologic udder edema is uncertain. Supplementing the ration of prepartum dairy cows with high concentrations of sodium or potassium salts significantly increases the incidence and severity of edema., However, serum biochemical values and fractional clearance of electrolytes are similar in affected and nonaffected cows.⁵¹⁴ Increased capillary hydrostatic pressure (resulting from changes in mammary blood flow and intramammary pressure that occur around parturition) might be involved, as might incompetent valves in the cranial superficial epigastric veins draining the udder.

First-calf heifers and high-producing cows are at greatest risk of developing udder edema. Other risk factors are not well documented. In a case-control study of heifers in Florida, the risk of udder edema increased as height of the heifer increased, was higher if calving occurred in winter than in summer, and was higher if the fetus was male rather than female.⁵¹⁶ Heifers with udder edema in the first lactation were more likely than unaffected heifers to develop edema in subsequent lactations.⁵¹⁶

Treatment of udder edema includes preventing excessive salt intake and administering a diuretic. In the United States, furosemide is labeled for use in dairy cows, has 48-hour milk­withholding and slaughter-withholding times, and is the diuretic of choice for treating udder edema. In one study, high cranial superficial epigastric venous pressure in cows with udder edema was reduced by IV administration of furosemide (500 mg) but not by hydrochlorothiazide (250 mg) or acetazolamide (500 mg).^507,515 Repeated administration of furosemide for several days should be avoided, but if repeated dosing is necessary, cows should be monitored for signs of electrolyte imbalance. Although corticosteroids have been recommended for treatment of udder edema, their efficacy is questionable. Prepartum milking reduces the severity of edema⁵¹⁷ but also decreases colostral immunoglobulin concentration at calving, so an alternative source of colostrum is needed. Prepartum milking of affected heifers has also been shown to reduce the risk of developing mastitis, but care should be taken to manage energy balance to prevent the development of ketosis.⁵⁰⁰ Milking first lactation animals four times daily did not reduce or increase udder edema scores.⁵¹⁸ Increased milking frequency or other testimonial treatments such as exercise have not been demon­strated to reduce udder edema.

BLOODY MILK. It is not uncommon to observe blood in postpartum mammary secretions. Small vessels may rupture as a result of trauma or in conjunction with udder edema. The milk is usually light pink to red or brown and may contain small blood clots. Antibiotic treatment is not indicated. Bloody milk can also accompany severe clinical mastitis or gangrenous mastitis, both of which have a poor prognosis, but physical examination of the animal will identify these conditions.

Bloody milk should be withheld from sale for human consumption. The milk usually returns to normal appearance within 1 week. However, because blood contains natural antimicrobial inhibitors, bloody milk may cause false-positive antibiotic residue test results. The IgG1 concentration of bloody colostrum is similar to that of normal-appearing colostrum, meaning that it is not necessary to discard colostrum simply

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because it contains blood.⁵¹⁹

TEAT AND SKIN CONDITIONS. Several noninfectious diseases of teats are recognized to occur.⁵⁵ The color and condition of teats can be influenced by milking equipment, overmilking, use of caustic chemicals, or environmental condi­tions. The development of hyperkeratosis of the teat ends is not uncommon and occurs more commonly during winter months. Hyperkeratosis is a thickening of skin that lines the teat canal and is the result of a localized hyperplasia of the stratum corneum.^48,55,520 Mild hyperkeratosis is a normal physi­ologic response to forces applied to the teat during milking and does not increase the risk of IMI. However, moderate and severe hyperkeratosis can become a problem. Various scoring systems have been developed to assess teat end health. In general, teats are scored on a 1 (N = no ring) to 4 (VR = very rough ring) based on the teat end callosity observed. It is recommended that herds have less than 20% scores of 3 (R = rough ring) and 4 and less than 10% scores of 4.⁵⁵ Rough teat ends not only are difficult to clean but also provide a surface for pathogenic bacteria to harbor.

Infectious lesion of teats have been associated with several viruses. Pseudocowpox is caused by a paravaccinia virus that can cause acute infection in cattle. This disease results in lesions that include center vesicles that ulcerate to form scabs. As the lesions heal, they result in a characteristic ring or horseshoe­shaped scab. This virus can affect the hands of milking techni­cians. Diagnosis is based on observation of lesions on the hands of milking technicians and teats. The condition is generally self-limiting within 3 to 5 weeks.

Bovine herpes mammillitis has been associated with both herpesvirus type II and herpesvirus type IV The resulting lesions appear similar and can occur either sporadically or in an outbreak. These viruses can present with a wide range of symptoms ranging from mild edema to the development of vesicles that result in severe ulceration and the formation of painful scabs. This condition appears to be more common during winter months. Diagnosis is based on observation of clinical signs and can be confirmed by histopathology. There is no effective therapy, but teat dipping using an effective germicide is recommended. This virus can spread among animals, so affected animals should be segregated and milked with separate milking equipment.

Teat warts are not uncommon and can be caused by several different papillomaviruses. The appearance of the warts is vari­able, ranging from small, smooth lesions to large, frond-like protuberences. Younger animals are often more susceptible and will develop immunity. Warts are generally self-limiting and will resolve within several months. No therapy is recommended.