THE MERCK VETERINARY MANUAL
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Physiologic Disorders of the Udder

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Udder edema is common in high-producing dairy cattle (especially heifers) 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 precalving period. Prepartum diets that contain excessive salt increase the severity of udder edema. Physiologic edema is not usually painful and occurs when pitting edema develops symmetrically in the udder prior to parturition. Udder edema is a risk factor for the development of clinical mastitis and occasionally can become a chronic condition that persists throughout lactation. 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, but the practice may predispose older cows to parturient paresis (see Parturient Paresis in Cows). 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.

Initiation of milk secretion in heifers prior to calving is occasionally noted. Precocious mammary development in a single gland sometimes results from suckling by herdmates. Symmetric mammary development has been occasionally associated with ovarian neoplasia or exposure to feedstuffs containing estrogen or contaminated by mycotoxins. Removal of contaminated feedstuffs generally results in resolution of the problem.

In rare instances, newly calved heifers may have problems with milk ejection. Fear of handling or unfamiliarity with the milking process is the usual cause. Care should be taken to ensure that animals are handled calmly and gently and that the milking routine provides for adequate stimulation (>20 sec) before attaching the milking unit. Administration of oxytocin (20 IU, IM) may be necessary in some instances.

Agalactia is seen occasionally in heifers and can be a primary endocrine problem or a localized problem of the mammary gland. In recently fresh cows, agalactia is occasionally caused by a severe systemic disease or by mastitis caused by Mycoplasma bovis. Agalactia has also been associated with cows grazing or eating endophyte-infested fescue.

These are usually the result of a severe infection, which may occur in dry or lactating cows or in heifers due to sucking by other heifers or calves. Some of these quarters may return to production in future lactations. Rarely, blind or nonfunctional quarters may be congenital.

Congenital aberrations include many structural defects, but the most significant disorder is supernumerary teats. These may be located on the udder behind the posterior teats, between the front and hind teats, or attached to either the front 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. Most are easily removed surgically when the heifer is from 1 wk to 1 yr old (best done at 3–8 mo of age). Supernumerary teats may be surgically removed from preparturient heifers before lactation begins. The incision should be sutured or stapled after teat removal.

Last full review/revision July 2011 by Pamela L. Ruegg, DVM, MPVM, DABVP (Dairy)

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