Udder Edema of Jersey Cattle Affected with Rectovaginal Constriction

Ten Jersey cows affected with rectovaginal constriction (RVC), which developed udder oedema near calving, were studied. One normal Jersey and 3 normal Holsteins served as controls. Before euthanasia the animals underwent daily clinical examination, with special emphasis on the size of the foramen in the rectus abdominis muscle (milk wells). The permeability of the mammary blood vessels was studied by giving one gram of 1% solution Evans blue i/v and examining changes in the colour of the milk and also of interstitial fluid collected by stab incisions. After euthanasia, the entire udder, milk veins, milk wells, subcutaneous tissues and muscles covering the abdomen were removed intact, except in two cows where udder vascular systems were studied by latex infusion. Fifteen minutes after Evans blue injection, the colour of the milk and interstitial fluid were whitish blue and yellowish blue respectively. Oedema involved the entire udder but was more pronounced ventrally. Microscopically there was excessive fluid infiltration between the muscle fibres of the subcutaneous tissues, in the interlobular and interalveolar interstitial spaces of the udder parenchyma, and in the supramammary lymph nodes. The latex studies showed that both milk veins were demarcated by ring-shaped depression of constrictions at the entrance of the milk wells. The studies with Evans blue demonstrated an increase in udder vascular filtration of fluid and protein, possibly due to enlargement or stretching of capillary pores. The latex studies suggested that the milk wells may be a restrictive point for venous blood flow from the udder. Udder oedema may be associated with RVC in Jersey cows.


Introduction
Constriction of the anus and vulvo-vestibular area(RVC) due to homozygosity of a simple autosomal recessive gene, has been described in Jersey cattle (13)(14)(15)19).Common problems, in addition to rectovaginal constriction, are difficulty in performing artificial insemination and pregnancy diagnosis, dystocia, and severe udder edema at calving time (14).
This report describes gross and microscopic pathological features of udder edema in Jersey cattle affected with rectovaginal constriction.

Animals.
Ten Jersey cows affected with rectovaginal constriction (RVC) which developed udder edema near calving, were used in this study.These cows were part of a herd used to study the genetics of RVC (Table 1).Four cows, one normal Jersey, and three normal Hosteins served as controls (Cases 11-14, Table 1).
The udder was clinically examined daily in the RVC Jersey cows to determ ine the stage of m axim um

RVC Udder
Edema Remarks development of udder edema.The subcutaneous abdominal veins (milk veins) were also clinically evaluated with special emphasis being placed on the size of the foramen in the rectus abdom inis muscle (milk wells) where the subcutaneous abdominal vein (milk veins) entered the abdominal cavity to join the internal thoracic veins.Before euthanizing, the RVC Jersey cows affected with udder edema were used to study the permeability of the mammary blood vessels to Evans blue.Four l-2 cm stab incisions of the skin were made in the ventral aspect of the udder to collect interstitial fluid.Milk was also collected from all four quarters of all cows during the height of udder edema.Following collection of control intersitial fluid and milk samples, one gram of 1% solution of Evans blue3 was aFisher Scientific Company, Fair Lawn, New Jersey 07401.

NOVEMBER, 1983
administered intravenously.This was followed by the collection of milk and interstitial fluid every 15 minutes for 2 hours.Changes in the color of the milk and interstitial fluid before and after Evans blue injection were monitored.
Necropsy Procedure.All cows were terminated and an im m ed iate sta n d a rd iz e d necropsy p ro ce d u re was performed.The entire udder, milk veins, milk wells, and the subcutaneous tissues and muscles covering the abdomen from all cows, except two cows that were used for latex infusion veins, milk wells, and the subcutaneous tissues and muscles covering the study, were removed intact.Careful gross exam ination was done on the udder skin, subcutaneous tissues, parenchyma, vessels, supramammary lymph nodes, pudendal arteries and veins, perineal arteries and veins, milk veins, and milk wells.
Histopathology.Sections from the above tissues were fixed in 10% buffered neutral formalin, processed routinely, sectioned 6 microns and stained by Van Gieson's and hematoxylin eosin (H&E) stain.
Latex Infusion.Two RVC-affected cows were randomally selected for studying udder vascular systems.Shortly following euthanasia, the abdominal cavity was crosssectioned through the area of the first lumbar vertebra.All abdominal viscera was removed, and the abdomianl aorta and vena cava were exposed and cannulated by a polyethelene canula.The blood vessels were immediately rinsed with heparinized salineb while the udder was intact.
The carcasses were placed in a cooler and a continuous infusion of 10% buffered neutral formalin was performed for 3 days.The formalin container was elevated approximately 2 meters higher than the level of the carcasses to keep high infusion pressure to the udder.After the 3 days of formalin infusion, red and blue latexc respectively, was infused into the aorta and vena cava.The carcasses were kept cool for two additional weeks.The udder was then removed and dissected.

Results
Clinical findings.All RVC Jersey cows exhibited typical signs of udder edema shortly before calving (Table 1; Figures 1 & 2).The milk veins were large and had tortuous course under the subcutaneous tissues, especially in older cows.
The incised skin, in cows with udder edema, allowed a yellow, straw-colored fluid to drip.The milk was a normal color.Fifteen minutes after Evans blue injection, the color of the milk and interstitial fluid were white-blue and yellowblue respectively, and the color stayed the same during the entire 2 hours of sampling.
Necropsy findings.In most cases, the edema involved all four mammary glands and was consistently located in the bHeparin Sodium 10 U.S.P. Units per ml o f saline.cBiological Center, 6780 Jackson Road, Ann Arbor, Michigan 48103.ventral aspect of the udder, especially in the rear aspect of the udder.The longitudinal and sagittal grooves of the udder were nearly obliterated.In some cases, the edema extended under the subcutaneous tissues to the umbilical region.
Ischemia and necrotic areas on the skin extending from the lateral aspect of the udder to the thigh were commonly seen (Figures 3 & 4).Skin incisions over the edematous areas resulted in cut surfaces with the oozing of smooth, glistening, yellow-blue fluid.The udder parenchyma were also edematous and filled with a blue, clear fluid.The interstitium were thick, edematous, and prominent.The left milk vein in one RVC Jersey cow was branching at the entrance of the left milk well into two branches.One branch went directly cranial and laterally while the other was directed cranially and medially.The supramammary lymph nodes were large and edematous.Incision in their surface  revealed a bluishcolored lymph, and the cut surfaces were smooth, glistened, and bulged.Microscopic findings.The most common features of the subcutaneous udder tissues were: edema that appeared as empty spaces between the muscle fibers.In some areas, an acidophilic, homogeneous, faintly stained edema fluid was seen.
The muscle fibers were disrupted and wrinkled.An increased amount of collagen fibers were present.The lymphatics were dilated, tortuous, and variable in size; some were larger than the size of the mammary alveoli.Other lymphatic vessels were ruptured.
The udder parenchyma was also edematous.The interlobular and interalveolar interstitial spaces were edematous.There were congested blood vessels and dilated lymphatics.Mononuclear cells, mostly lymphocytes and eosinophils, were interspersed in the fibrous tissues.The alveolar epithelial cells appeared hyperplastic, and the cytoplasm was almost completely filled with vacuoles.
The supramammary lymph nodes were also edematous.Microscopic changes in the blood vessels were characterized by marked dilation in some venules and arterioles in the udder parenchyma while other venules and arterioles, as well as the milk vein, in RVC Jersey cows were characterized by medial thickening.Van Gieson's stain showed thickening of the tunica media with collagen fibers that appeared as wavy bands running parallel to one another within the tunica media.
Anatomical findings.All arteries and veins were filled with latex red and blue, respectively.Upon udder dissection, the pudendal arteries and veins, the perineal arteries and veins, and their branches were normal.
Arterioles and venules were mostly located in the ventral aspect of the udder, especially near the subcutaneous tissues and around the perineal vessels.Both milk veins were demarcated by ring shape depression of constrictions at the entrance of the milk wells.Discussion RVC Jersey cows consistently developed udder edema a few days to a few weeks before calving.Latex infusion studies suggested that the milk wells may be a restrictive point for venous blood flow from the udder resulting in increased venous pressure.The increased pressure results in in tra ly m p h a tic c o n g estio n , m e c h a n ic a l-fu n c tio n a l insufficiency of lymph flow, and resulting edema (25).The constriction of the milk wells may be another factor in these RVC Jersey cattle similar to the constriction of the anus and vestibule (13-15).
Our studies with Evans blue demonstrated that there in an increase in udder vascular filtration of fluid and protein.It has been suggested that increased capillary permeability to macromolecules may be the result of capillary pores enlarging or stretching (28).It has been further concluded that elevation of venous blood pressure increases the filtra tion of fluid from the capillary blood into the tissue spaces approximately in proportion to the rise of venous pressure (9.32).
We were unable to determine whether the increased filtration occurred in the capillaries, venules, or arterioles.Recently, the use of a colloidal carbon technique in a study on ultrastructural changes associated with pulmonary edema dem onstrated th at A lpha-N aphthyl-T hiourea (ANTU) caused an increase in permeability of all the capillaries, venules, and arterioles (2,7,16).
Edema does not arise unless the lymphatics are unable to drain the increased interstitial fluid.The appearance of Evans blue in the milk indicated there was excretion of Evans blue protein complex into the udder acini.In addition to the lymphatics, another system of removing excess interstitial fluid reported was an overflow system into the lung alveoli, the intestinal lumen, and peritoneal cavity (34).

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Histopathological findings demonstrated marked edema in th e s u b c u ta n e o u s tis s u e s , p a re n c h y m a , and supramammary lymph nodes of the udder.Dilation of the venules and the increased collagen deposition in the tunica media of the milk veins may be caused either by the phlebohypertension or an inherited characteristic in this breed of cattle.

Summary
Udder edema is a factor which may be associated with rectovaginal constriction (RVC) in Jersey cattle.Fourteen cows, ten Jersey cows affected with RVC and four normal controls (1 Jersey and 3 Holstein), were used to study the pathological changes in the mammary gland associated with udder edema.Edema involved the entire udder in the Jersey cows affected with RVC but was more pronounced in the ventral aspect and was due to increased vascular filtration of fluid and proteins.
Microscopically, the edematous udder was characterized by excessive fluid infiltration between the muscle fibers of the subcutaneous tissues, the interlobular and the interalveolar interstitial spaces of the udder parenchyma and into the supramammary lymph nodes.
Anatomical studies demonstrated abnormalties of the milk vein and milk wells in some RVC cows.Thus, udder edema appears to be a facultative factor associated with RVC in Jersey cows.

Fig. 1
Fig. 1 Udder of RVC Jersey cow affected with udder edema shortly before calving.

Fig. 2
Fig. 2 Udder of RVC Jersey cow affected with udder edema shortly before calving.Notice finger imprints on udder.

Fig. 3
Fig. 3 Udder of RVC Jersey cow affected with udder edema after calving.N otice deep cracks into udder tissue.

Fig. 4
Fig. 4 Udder of RVC Jersey cow affected with udder edema after calving.Notice necrotic areas on skin of udder and thigh.

TABLE 1 .
Edema cases and other data in RVC Jersey and Controls