Physiologic Disorders of the Udder in Cows

Udder edema is common in high-producing dairy cows (especially heifers) immediately before and after parturition. Predisposing causes include age at first calving (older heifers are at greater risk), gestation length, genetics, nutritional management, obesity, and lack of exercise during the antepartum period.

Antepartum diets that contain excessive salt increase the severity of udder edema. Hence, udder edema may present as a herd management problem. Distention of the udder makes milking cluster attachment difficult and milk flow may be impaired, leading to teat condition problems. Acute physiologic edema is not usually painful, developing symmetrically in the udder before parturition, mostly commonly in heifers. The skin is tight and finger pressure leaves a depression (pitting). It usually resolves within a week of parturition.

Persistent (chronic) edema is usually localized ventrally and may last through lactation. It has been associated with chronic hypomagnesemia. Udder edema is a risk factor for development of clinical mastitis.

Treatment should be initiated if swelling threatens the udder support apparatus or if edema interferes with the ability to milk the cow. Edema can be treated by milking cows before parturition. Positive effects of premilking in heifers have been reported; however, the practice may predispose older cows to parturient paresis. Massage, repeated as often as possible, and hot compresses stimulate circulation and promote edema reduction. Diuretics have proved highly beneficial in reducing udder edema, and corticosteroids may be helpful. Products that combine diuretics and corticosteroids are available for treatment of udder edema.

Heifers may secrete milk before parturition. This can be induced in the whole udder by milking machine. Occurrence in a single gland usually results from suckling by a herdmate. Symmetric mammary development has been associated with ovarian neoplasia or exposure to feedstuffs containing estrogens or contaminated by mycotoxins. Removal of contaminated feedstuffs generally results in resolution of the problem.

Newly calved heifers may have problems with milk ejection. Fear of handling or unfamiliarity with the milking facility or milking procedures is the usual cause. Heifers should be made accustomed to the milking parlor, and its surrounds, and the general handling process before parturition. Care should be taken to ensure that animals are handled calmly and gently, and that the milking routine provides for adequate stimulation (>20 seconds) before attaching the milking unit. Oxytocin (20 U, IM, repeated as necessary to promote milk letdown) may be necessary for induction of milk letdown in some instances; however, repeated doses should be gradually reduced to avoid dependence on administration of exogenous oxytocin.

Agalactia (failure to produce milk) occurs occasionally in heifers and can be a primary endocrine problem or a localized problem of the mammary gland. It is occasionally due to a severe systemic disease, eg, by Mycoplasma bovis or by mastitis due to Trueperella pyogenes. Agalactia has also been associated with cows grazing or eating endophyte-infested tall fescue.

Nonfunctional (blind) quarters are usually the result of a severe mastitis infection, which may occur in dry or lactating cows or in antepartum heifers. Some of these quarters may occasionally return to production in future lactations. Rarely, blind or nonfunctional quarters may be congenital.

Congenital aberrations include many structural defects; however, the most important disorder is supernumerary teats. These may be located on the udder behind the hind teats, between the fore and hind teats, or attached to either the fore or hind teats. Removal of supernumerary teats from dairy heifers is desirable to improve appearance of the udder, to eliminate the possibility of mastitis in the gland above the extra teats, and to facilitate milking, if they are close to functional teats. Most are easily removed surgically when the heifer is from 1 week to 1 year old, often at the time of horn disbudding. Supernumerary teats may be surgically removed from antepartum heifers before lactation begins. The incision should be sutured or stapled after excision of the teat. Permanent fistulas into the teat or gland cisterns are best repaired in heifers prior to calving or during the dry period for cows.