Physiologic Disorders of the Udder
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 before parturition. Udder edema is a risk factor for 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 before 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 facility or milking procedures 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, but doses should be gradually reduced to avoid dependence on administration of exogenous oxytocin.
Agalactia is seen occasionally in heifers and can be a primary endocrine problem or a localized problem of the mammary gland. It 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.
Nonfunctional quarters are usually the result of a severe mastitis infection, which may occur in dry or lactating cows or in heifers due to suckling by other heifers or calves. 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, 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 excision of the teat.