Uterine torsion

Key words: uterus, torsion, bovine, accident, pregnancy

Uterine torsion is not uncommon in cows. It is seldom encountered in heifers and is also infrequent in Bos taurus var indicus cattle. The reasons for those findings are not clear but have been related to large, deep and expansive abdomens in affected breeds and parity. Uterine torsion is also more common in unfit dairy cows kept in barns than those at pasture; perhaps a consequence of poor abdominal muscle tone and weak limbs allowing sudden jerky movements.  Not surprisingly, uterine torsion has also been related to poor uterine tone and hypocalcemia.

One only has to appreciate how the hind quarters of a cow are elevated above its thorax when it rises or lies down to imagine how the stability its pendulous uterus becomes precarious in that posture.  The inherently poor stability the bovine uterus adds to this predisposition. Consider the attachment and flaccidity of the mesometrium in cattle. This allows one to easily retract and manipulate a non-pregnant bovine uterus during transrectal palpation. During pregnancy the mesometrium offers even less support as the pregnant uterus expands cranially, beyond the cranial margin of the mesometrium.

In twin pregnancies, the uterus is more evenly loaded and is a result, more stable. Not surprisingly, uterine torsion is comparatively rare in cows with twin pregnancies.

Uterine torsion occurs in all ruminants and even multiparous animals but is most common in cows and horses, especially cows. In horses, mesometrial support is far more substantial than it is in cattle. One only has to try to retract an equine uterus to appreciate that reality. Even during pregnancy, the equine uterus is more stable than a bovine uterus. Also, mares change from the lying to standing posture by raising their forequarters first, so the equine uterus seldom finds itself in a pendulous state. The cause of uterine torsion is different between the two species; in cattle, as explained, it is due to uterine instability during early parturition. In mares it appears to be related to mares rolling in pasture during mid to late gestation; perhaps as they shed their winter coats.

In this entry, all descriptions of the direction of torsion are written as if one is looking at the cow, caudal-to-cranial. In that regard, anti-clockwise torsion is more common than vice versa. The reason for this is not obvious and the author's speculation will not add to the value of this entry. In the case discussed here, torsion was in a clockwise direction.

Figure 1: The mechanism of uterine torsion in cattle. In this illustration the uterus has twisted clockwise, pulling the left mesometrial ligament (LM) over to the right, cranial to the right mesometrial ligament (RM). The arrow indicates the direction of torsion. Size available: 900 x 551px

This illustration is found elsewhere in various manifestations on the Internet. However, the original image was drawn by Dr Ronald Trengrove circa 1971. Shortly before his death in 2014, Dr Trengrove gave the author permission to use and edit his veterinary drawings.  font-weight: normal>

In rare cases, uterine torsion can occur during mid gestation but it is usually a condition associated with calving. Typically, a cow affected with uterine torsion will show cessation of calving but continuing signs of discomfort. The farmer notes the typical mucous discharge from the vulva (see figure 2) the presence of colostrum,  and obvious signs of impending  parturition. Then there is no further progress. After several hours of inactivity but persisting discomfort, a veterinarian is called.

Figure 2: A pluriparous cow with uterine torsion, several hours after the onset of calving. Note the copious clear vulva discharge and distended udder. In this case, there was no obvious distortion of the vulva lips; an occasional finding in these cases. Size available: 1149 x 1159px.

If the fetus or its membranes have entered the vagina, there may be a degree of straining.  On transrectal examination, a tight mesometrial ligament can be felt stretching across the caudal abdominal cavity. Torsion of the uterus may be palpable per rectum as a corkscrew to the left or right-hand side. On vaginal examination, torsion is usually detected, but in a few cases, the site of torsion is cranial to the cervix and vaginal torsion may be absent. If the cervix has dilated, fetal limbs may be in the vagina. Often however, uterine torsion occurs before the cervix has dilated completely. If torsion is not relieved, fetal death, putrefaction and toxemia will result.
.

Figure 3: An operator (Dr J. Spears) determining  the severity of torsion and patency of the cervix.  Perhaps obviously, the cervix was indeed patent in this case; open enough to allow the operator to place a lubrication tube and calving chains. As a result rolling (described later in this entry) was not required. Size available: 1600 x 1200px

Figure 4: This image shows two obstetrical chains and a Cornell detorsion rod about to be used to rotate the calf in a clockwise direction. Size available: 1175 x 1172px

Figure 5: In this case the operator has elected to use a Cornell detorsion rod to rotate the fetus. The two red arrows in the inset image show how the calves legs are placed through loops of the calving chains prior to detorsion. The inset shows how a single chain can be use with the detorsion rod. In this case however, the operator chose to use two chains with the detorsion rod. Size available: 2203 x 1556px

A plastic device named "Gyn-Stick", similar to the Cornell detorsion rod, is available from Jorgensen labs.  It is made from rigid plastic and uses calving ropes in place of chains. Its use is shown in this commercial video.

The author was introduced to  the Cammerer's detorsion fork as an undergraduate in 1972. It is shown in figure 5, a diagram by the author. The commercial product can be seen on this website, still commercially available. In the author's opinion it is preferable to Cornell-style instruments because large cuffs spread the torsion load on the limbs and the fork enlarges the radius of rotation compared to other detorsion instruments.

Figure 5: A Cammerer's* detorsion fork' often referred as a torsion fork. Size available: 624 x 1132px

Figure 6: After successful detorsion, the cervix of the cow was dilated manually over a period of 15 to 20 minutes prior to extraction and the calf. The obstetrics chains were moved distally from their original positions on the left and right proximal radius and ulna; they were placed on conventional traction sites, above each fetlock joint. As is usually the case, the chains were also thrown into a half hitch proximal to each pastern joint.  Size available: 1409 x 1119px

Figure 7: Torsion was then used to rotate the calf by 110 to120 degrees into a dorso-left-ilial position to prevent hiplock; a normal part of mutation and traction in any assisted calving. Size available: 1600 x 1200px

Figure 8: The calf was dead in this case probably because torsion was protracted and severe. In one large study (Klaus-Halla, D. et al. 2018) 35 percent of calves were delivered live if the case was treated within 12 hours after the onset of calving and approximately 90% if treatment began within 6 hours. Size available: 942 x 1461px

In some cases the cervix has not yet dilated at the time of presentation or the uterus has twisted to such an extent as to preclude entry by the operator. In those cases, the cow must be rolled to relieve torsion. After torsion is relieved, it is possible to determine if the cervix and body of the uterus can be accessed to deliver the calf. Fortunately, in the majority of cases, the cervix will have dilated enough to permit per vagina mutation.

In the opinion of some, if cervical dilation is insufficient to allow per vagina delivery after rolling, one should wait for at least three hours for this to occur. However, the cervix may never dilate sufficiently in some cases and even if the cervix does dilate, a second visit to the farm will be required at extra cost; only to deliver a dead calf. In the author's opinion therefore, it is preferable to perform a Cesarean section immediately after rolling in those cases.

Even if the cervix is closed and it appears impossible to deliver the calf per vagina, the cow should be rolled to correct torsion. This will facilitate Cesarean section if it is required. In the event that a Cesarean is attempted before torsion is corrected, the uterus, once freed of the weight of the calf, may contract and rotate away from the surgeon. This makes the uterine wall difficult to suture.

A highly experienced colleague responded to this statement by saying that his standard approach to torsion is to perform a cesarean section immediately in all cases of torsion.

The technique of "rolling" is shown in figure 9.

Figure 9: Correction of uterine torsion by rolling (Schaffers’* method). The uterus has twisted clockwise in this case. This is shown by the inner, circular red arrow “a”. An attempt is made to roll the cow in the same direction (large red arrow) as the uterus has twisted so that the cow twists around her own uterus. A plank is often used to facilitate this process with pressure applied to the cow's abdomen, just cranial to her udder. During rolling, pressure on the uterus helps to prevent rotation of the twisted uterine horn. Although the affected uterine does not rotate during rolling, it could be said that it rotates anticlockwise relative to the cow. In this case that would be in the direction shown by the circular green arrow “b”.  If  rolling successful, fetal fluids usually escape from the cow's vulva lips immediately after torsion is relieved. An attempt should then be made to mutate and extract the calf. Size available: 1200 x 894px

*The author has been unable to determine the exact origin of the eponym Cammerer  Any assistance in that regard will be appreciated. Schaffer published on his plank modification for uterine torsion in 1946 (see references). 

Selected references:

Frazer, G.S. 1996. Bovine uterine torsion: 164 hospital referral cases. Theriogenology. 46:739-758

Klaus-Halla, D. et al. 2018 In German. Translated: [Uterine torsion in cattle: Treatment, risk of injury for the cow and prognosis for the calf] Tierarztliche Praxis. 46:143-148 

Lyons N et al. 2013. Clinical forum: Bovine uterine torsion. Livestock. 18: 18-24

Pascale, A. et al 2008. A study of 55 field cases of uterine torsion in dairy cattle. Can Vet J. 49:366–372

Roberts. S.J. Veterinary obstetrics and genital diseases (Theriogenology). Published by the author. Uterine torsion. pp 230-233

Roelofsen, J.M.P. 2018 Uterine Torsion in relation to blood calcium concentration in dairy cattle. Masters Thesis University of Utrecht.

Schaffer W. 1946. Schweizer Arch. Tierheilk 88: 44.

Uterine endometrial fissures

Key words: bovine, endometrium, fissures, uterus, postpartum, pyometra

The opened uterus shown below (image 1) was obtained from a seven-year-old Holstein cow in poor body condition. She was euthanized and submitted for postmortem examination because of infertility and continual loss of weight. Her history of postpartum estrous cycles was unknown.

Image 1, size available: 2005 x 1350 px

Apart from mild subacute suppurative broncopneumonia, the most noticeable feature in this cow was her moderately enlarged uterus, especially the right uterine horn. The uterus was turgid and distended with a large volume (perhaps 2 liters) of cloudy, tan colored, watery pus. The cervix was closed, not allowing any passage of the purulent material into the vagina. 

It is possible that pyometra had been supported by a corpus luteum (CL) formed from a postpartum ovulation (the common situation in pyometra) because a corpus albicans (CA) was present in her left ovary. However, the CA formed from the regression the CL of pregnancy can persist for extended periods after calving so that possibility is questionable. Therefore and most likely, one is left with the remarkable situation where the cervix was closed as is the case in common pyometra, yet there was an absence of luteal tissue to support that condition. More remarkable however, were the multifocal deep fissure-like ulcerations on the endometrium (image 2). These are shown, partially covered by purulent exudate in the right half of the image above. The largest of these measured 2 cm at its widest point. 

Image 2, size available: 3005 x 1773px

As indicated by the yellow arrows in the image above, the fissures were visible from the peritoneal surface as well. The serosal surface of the uterus was covered with a fine layer of yellowish fibrin, indicating an extension to local peritonitis.

Histopathology showed multiple small abscesses within these fissures. Neutrophils were the predominant cell type, accompanied by a low population of mononuclear cells. Culture of the uterine exudate produced no microbial growth; not particularly rare in a purulent environment.

Fissures such as these are not characteristic of common cases of pyometra due to Trueperella pyogenes (formally assigned successively to the the genera Corynebacterium, Actinomyces, then Arcanobacter). Despite an interest in reproductive pathology spanning many years, this author is unaware of similar cases and solicits the input of colleagues in this regard. Certainly, partial circumferential-splitting of the endometrium is a feature usually not seen in pyometra, even in uteruses distended with large volumes of pus.

An involuting uterus, late postpartum

Keywords: uterus, vagina, bovine, corpus luteum, postpartum, cervix

The uterus of a cow that had involuted partially after calving. She had also ovulated at least once after calving.

Image size: 1308 x 972px

The presence of a corpus luteum (CL) in the left ovary indicates that she had ovulated recently.  Some may ask: Why is it that a cow would ovulate before her uterus is fully involuted and ready to accept a new pregnancy? The answer is that this cow's calf was removed shortly after birth and was not allowed to suckle i.e. this tract was from a dairy cow, a product of human manipulation. Dairy cows are not subjected to the negative effect of sucking on postpartum anestrus. By contrast, beef cows are suckled and do not ovulate for extended periods after calving (depending on breed and nutrition) usually well after the time that the uterus has taken to involute completely.  In the right ovary of this cow, a small follicles has formed a layer of luteal tissue within the follicle, a sign of low level stimulation with luteinizing hormone (LH). Although it is smaller than most cystic follicles it is essentially just that; a luteinized cystic follicle. It is possible that this cystic follicle could have persisted beyond the lifespan of the CL in the left ovary, causing the cow to have a delayed return to estrus (as is often the case). However it is also possible that it was of a similar age to the CL, failing to mature and ovulate as a twin ovulation.  Finally, note that there is no shortage of small tertiary follicles in these ovaries, waiting to participate in postpartum estrous cycles. This is because the production of follicle stimulating hormone (FSH) recovers far sooner that LH production after a calf is born.

The caruncles in this specimen are small and almost completely involuted yet discoloration in the centers on the caruncles suggests that their involution is not complete. The endometrium between caruncles is sloughed soon after calving but is restored by 10 to 12 days postpartum. The caruncles by contrast, have only sloughed tissue to the level of their capillary beds by that time and it is only by about 35 days  postpartum that caruncles are completely restored with new epithelium. Interestingly, caruncles visible throughout the life of the cow. In fact they are even evident when females calves are developing in utero.

Note the short uterine body i.e. how quickly the horns divide as an object ascends into the tract. This is important for several reasons. First, if one is to preferentially inseminate in one horn or another, the pipette must be directed accordingly, as soon as the internal cervical os has been reached, A similar situation is encountered when one has to collect embryos from one horn or another. Finally, because of the virtual absence of a uterine body, bovine fetuses are highly likely to be in longitudinal presentation at calving. By contrast, mares have long uterine bodies making transverse presentation more likely than in cows (although thankfully, transverse presentations are still unusual in mares). Also, no thought is given to horn selection in mares during routine insemination or embryo flushing.

Note the cervical "rings". Apart from the ring that surrounds the external cervical os, these structures are more akin to crescents than complete rings. One must negotiate these rings with an insemination pipettes during artificial insemination (AI). In mares, these rings do not exist and entry into the uterus is simple. In cattle by contrast, the cervix must be grasped per rectum and the tip of the A.I pipette placed in the fornix of the vagina. Then the external cervical os is then manipulated over the instrument while the instrument itself is eased through the cervical canal. The same situation is encountered when one flushes embryos from the uterus.

Interestingly, the word fornix is derived from the Latin word for archway. In homo sapiens, standing erect, this is perhaps appropriate. In domestic animals however, the arches (around the cervix) have fallen on their sides!

Selected reference:

The mind of an aging theriogenologist.

Uterus, 20 days postpartum

Keywords: bovine, uterus, caruncles, palpation, involution, postpartum, follicles

During transrectal palpation, one can place a hand over the cranial margin of the uterus by about 10 to 12 days after calving. By 20 days (as in this case) one can usually retract the uterus for palpation. Although tissue from the caruncles has been shed down to the capillary layer by 10 to 14 days postpartum, the bases of the caruncles (white arrows) are still palpable at this time. If the endometrium is exposed, they are obvious, even at 30 to 35 days, when the uterus is fully involuted. Incidentally, lochial discharge is almost complete in normal cows (suckled or non-sucked) by this stage of involution.

Image size:1500 x 964px

Note that there is substantial ovarian activity in the form of follicle growth (yellow arrows) serving to remind one that FSH is not a limiting factor in the return to cyclicity in cattle. Follicles may ovulate as early as 10 to 14 days in non-suckled (dairy) cows but even though follicles such as these are present early in the postpartum period in almost all cattle, suckled cattle ovulate much later, LH being the limiting factor in those animals.

Uterine retraction

Keywords: retraction, uterus, palpation, amnion, membrane, slip, uterus, ovaries, examination, pregnancy diagnosis

The image below illustrates in part, a technique known as uterine retraction. Uterine retraction is in essence, the process of bringing the whole reproductive tract into reach for easy and accurate examination. The tract is passed through ones hand without releasing it through the entire examination.

The parts of the tract and its adnexa have been labeled in the black and white image below, serving as a key for the main image.

Image size: 1224 x 638 px

There are variations as to how an operator may retract the uterus during transrectal palpation. Some may place a thumb under the lateral aspect of a uterine horn, lifting the horn so that the ventral inter-cornual ligament can be brought close enough to grasp. This technique has been referred to as "indirect" retraction. Others (including the author) prefer a "direct" method, grasping the cervix around its circumference and moving it caudo-dorsally so the intercornual ligament is elevated and made accessible.

The ventral intercornual ligament is larger and stronger than the dorsal ligament. Therefore, only the ventral ligament is used to retract the uterus.

Once the intercornual ligaments are accessible, the ventral intercornual ligament is hooked with one or more fingers. Then the uterine horns are raised and "flipped" dorso-caudally so that the tract becomes doubled over on itself. It is held in this position while the operator's hand "crawls" along the uterine horns, "feeding" them under the hand at the same time. The uterus is examined for fetal membrane slipping and abnormalities such as free fluid, tumors and so on. Like the uterus, the ovaries and their adnexa can be moved extensively in cattle. Therefore the ovary on either side can be reached easily in most animals through the "crawling" and "feeding" motions described above.

In some animals rectal tone makes it difficult to palpate structures and patience is called for. In cows with epidural anesthesia, the rectum may dilate with air, also making transrectal palpation a challenge.

Although retraction is not necessary in every case, it is usually essential for accurate assessment of the tract. When structures such as early pregnancies are not detected, it is usually because the operator has grasped sections of the uterus and has dropped the tract intermittently during palpation.

Note on retraction in other species: Although camelids do not have an intercornual ligament, the non-pregnant uterus can be retracted by cupping the whole uterus and flipping it up in a dorso-caudal direction. Great caution must be exercised when examining smaller camelids; in some alpacas it may not be possible to perform transrectal palpation safely. In horses it is neither possible nor necessary to retract the uterus for accurate transrectal examination. The equine tract is well suspended by the mesometrium, making its position predictable and easy to locate. Also, mesocervical and mesometrial tension in mares make it impossible to grasp the cervix and retract the uterus.

The uterine arteries

Keywords: uterus, artery, middle, arteries, anatomy

During transrectal palpation of the pregnant bovine uterus, it is common to feel for the presence of fremitus in a uterine artery. A video of a windsock, simulating fremitus can be seen here. It shows non-linear, turbulent flow of air through a windsock; the sock is unable to constrain the airflow in a linear, orderly fashion. During pregnancy in ruminants, blood flow to the uterus increases rapidly, exceeding the ability to contain the blood flow in a linear flow. The effect is the same in both cases.

Since antiquity, this artery has been referred to by clinicians as the middle uterine artery, implying that there are several major arteries within the mesometrium. Indeed, this is clearly the case as shown below (A, B & C...perhaps more). However, the image also shows that there is only one major uterine artery (UA) from which the smaller arteries emanate. That artery should correctly be referred to as the uterine artery.

Image size: 1500 x 1000px

The question arises as to which of these arteries can develop fremitus during pregnancy. Clearly the major artery is capable of doing so. Therefore if there is any doubt as to which artery one is grasping during pregnancy diagnosis, it may be most correct to refer to "fremitus in the uterine artery" rather that "fremitus in the middle uterine artery". Finally, there is clearly potential for the development of an even number of large arteries in the mesometrium, in which case there can be no middle artery. Collectively therefore, the term "middle uterine artery" is probably incorrect in many instances of transrectal palpation. In the absence of clinical evidence to show otherwise, the term "uterine artery" should  be used.

Severe adhesions

Keywords: adhesions, inflammation, uterus, infertility, bovine

This bovine reproductive tract was from a slaughter plant specimen.

Image size: 3307 x 4218px

Severe adhesions arising from an inflammatory process were present around the ovaries and adnexa, obscuring the anatomy of those structures. Adhesions were also present over the entire surface of the ovary. Readers are encouraged to see the extent of these adhesions by clicking on this large image. However, to fully appreciate the adhesions, it should be downloaded by right-clicking on the image, saving it, then viewing it in an appropriate program.

The cow from whence this uterus came was either infertile or sterile as a result of these lesions; probably the reason for which she was culled.

Adhesions such as these can arise from endometritis due to a multitude of bacteria including Mycobacterium bovis (less so M. bovigenitalum), Fusobacterium necrophorum, Bacteroides spp.
Escherichia coli  and commonly, Trueperella pyogenes (previously known as Corynebacterium pyogenes and after that, Arcanobacterium pyogenes but recently renamed to  Trueperella pyogenes ).

The cow has a utero-tubal junction that does nor perform adequately as a one-way valve between the uterus and uterine tubes (fallopian tubes). Therefore ascending infections of the ovaries and adnexa are common in cases of metritis. Comparatively speaking, mares are far less inclined to this pathology because of a well developed utero-tubal junction that appears to function as a one-way valve. In humans, the utero-tubal junction is far larger than in any domestic animal and is a virtual highway to the ovaries. Therefore peri-ovarian adhesions are a major cause of infertility in humans. So called "pelvic inflammatory disease" is well known in women.

It is also possible for adhesions such as these to form as a result of peritonitis following a laparotomy; commonly a cesarian section. In this case it was impossible to detect a uterine incision scar because of the adhesions. The etiology of adhesions in this case is unknown.

A pregnant bovine uterus with leucosis

Keywords: leucosis, uterus, bovine, cow, pregnant, BLV

A uterus was examined from a six year old Holstein cow after two lactations; pregnant for a third time. The cow had been losing weight, her milk production had diminished unexpectedly and she had begun to show ataxia. Not being a valuable asset to the herd, she was culled and submitted for postmortem examination.

The cow had been bred 54 days before the date of culling. Interestingly, a highly experienced bovine practitioner had palpated her uterus transrectally shortly before breeding and found it to be apparently normal. Yet, approximately 60 days later, the same practitioner reported that uterus was both rigid and thick-walled. As shown below, ultrasonography revealed a grossly thickened uterine wall and a live fetus with a normal heart rate (~ 190bpm).

(Ultrasonographic image copyright: Dr B. Crane. AVC)

Image size: 574 x 435px

This finding suggested that the neoplastic process had developed very rapidly; a common finding in leucosis.

Based on histopathology, lymphomatous masses were present in numerous locations including internal lymph nodes, kidneys, the right atrium, the abomasum and in the spinal epidural space. The subdural lesions probably accounted for ataxia exhibited by the cow. Findings in the uterus are shown below.

Image size: 1189 x 1000px

There was diffuse but variable thickening of the myometrium with lymphomas, creating a friable uterine wall that developed fissure lines where it was manipulated. There were also several lymphoma nodules in the vagina. Surprisingly, the 54 day old fetus and its membranes were not autolysed, indicating that the fetus had probably survived until the time of euthanasia of the dam. 

Notes: There are several forms of lymphosarcoma in cattle but only one form has a known etiology i.e. bovine leucosis, caused by the bovine leucosis retrovirus (BLV). Bovine leucosis is not considered to be a common cause of abortion, probably because so few animals that are carrying BLV actually become symptomatic. However, as is evident from this case, leucosis does have the potential to cause abortion in cattle. 

Transfer of BLV is usually vertical and must occur by cell transfer, therefore events such as calving, surgical intervention, dehorning and even transrectal palpation have been incriminated. However, recent data has shown that transrectal palpation may not be as significant in the transmission of leucosis as once believed.

No vaccine is available for the control of bovine leucosis so control is often exercised by culling of test-positive animals. Fortunately, BLV is not transmitted during embryo transfer. Therefore embryos from BLV positive cows can safely be transferred to BLV negative surrogate heifers.

Uterine leiomyoma in a cow

Keywords: leiomyoma, bovine, uterus, histology


Enlargement seen in the left uterine horn of a pluriparous cow sent to slaughter suggestive of a leiomyoma.

Image size: 4788 x 3456 px

A close-up view of the transected tumor:

Image size: 5040 x 3456 px

The histopathology of this tumor was classic for that of a leiomyoma. It was well encapsulated and for the most part, its cells resembled those of normal smooth muscle. No mitoses were seen. In most areas there were whorled fascicles of smooth muscle cells separated by a fibrous stroma:

Image size: 1360 x 1024 px

In some areas however, the typical muscle fascicles became extensive fields of hyalinized stroma with entrapped smooth muscle cells:

Image size: 1360 x 1024 px

The incidence of genital leiomyomas is low in cattle, literature suggestion about one in 200,000. By contrast  leiomyomas are among the most common reproductive tumors reported in women and bitches, and are highly estrogen dependent in both. Their dependence on estrogen in cattle is unknown. In cattle, they are found throughout the tubular reproductive tract, even in the cervix.

Normal lochia from a dairy cow

Keywords: lochia, postpartum, bovine, cow, involution, uterus

Image size: 1200 x 1600px

Normal lochia from a dairy cow at 12 days postpartum; seen in its bedding. At this time, the sloughing process of the caruncles reaches the capillary beds, releasing red blood cells into the lumen. Therefore this discharge is normal and in the absence of fever, inappetence and other common pathology at calving (mastitis, traumatic reticulo-pericarditis etc) it requires no treatment.

Bovine uterine involution

Key words: bovine, involution, uterus, cycling, estrous, cycles, postpartum, palpation

The uterus of a cow, two weeks after calving, opened to show the state of involution. At this stage of involution, the areas of the endometrium have already involuted (this occurs by about 10 days after calving) but the caruncles themselves have not even sloughed their epithelium completely. It is only by 12 to 14 days that (at about the stage of the uterus in this image) that the sloughing process reaches the capillary beds, releasing red blood cells into the lumen. It also at this time, that neutrophils enter the lumen, attracted by chemotaxis to the contaminated lochia. Therefore lochia that are somewhat purulent and blood tinged at this time are normal.

The contents of the uterus are normally contaminated (not infected) by bacteria up until 25 to 30 days postpartum. The bacterial swab in the inset has been added as a reminder to this fact. Uterine cultures taken before this time are of limited value.

Image size: 1229 x 1162px

During transrectal palpation, it is only possible to grasp the cranial border of the uterus by this stage of involution i.e. 10 to 14 days after calving; much later than in mares. The size of an average human hand is given to scale to allow one to appreciate that challenge. Depending on management and health of the animal it has returned to its pre-pregnancy size by about 35 days after calving; in some reports as early as 25 days; in others, as late as 50 days. It is easily retracted at that time. After calving, the uterus of a cow is always larger than that of a heifer.

Although the corpus luteum of pregnancy is visible for several weeks after parturition (see the inset at right above) it has ceased to function at the time of calving.

Uterine involution is, for all practical purposes, disconnected from ovarian function in cattle. It is also disconnected from estrous behavior. In dairy cows (where human interference prevents calves from suckling) the first ovulations after calving often occur before 20 days postpartum but those ovulations are seldom accompanied by signs of estrus. Over the next two to three ovulations (which occur at increasing intervals between one another) estrous display becomes more obvious. Interestingly, the process of uterine involution is slower than both the resumption of normal ovarian activity and estrous display.

Although the epithelial regeneration over the caruncles is largely complete by 30 to 35 days postpartum, global involution of the uterus continues over the next 10 to 15 days. Certainly, the uterus is completely involuted by 70 to 75 days, when the first inseminations start occurring after calving in most dairy cattle i.e. the "voluntary waiting period". In beef animals, where suckling occurs, and breed and energy intake can also have profound negative effects on postpartum anestrous intervals, uterine involution is complete long before re-breeding occurs and is seldom a limiting factor in postpartum fertility.

Note of interest: Although the complex physiology of postpartum anestrus (nutrition, breed, presence of milk in the udder, calf contact etc) is still not completely understood, one of the cornerstones of anestrus appears to be a lack of LH secretion. Strangely, FSH secretion is a not a limiting factor in the resumption of cyclicity, well developed follicle populations being plentiful well before the first ovulations occur. A major negative effect on LH secretion is that of endogenous opioids (endorphins). This is not only true for cattle in the postpartum period but for mammals in general, including humans. LH secretion increases almost immediately after morphine antagonists such as naloxone and naltrexone are administered.

Leucosis in the uterus of a pregnant cow

Keywords: leucosis, bovine, neoplasia, BLV, pregnant

Image size: 1000 x 967px

Leucosis seen in the dorsal wall of the body of the uterus in a pregnant cow. This tract was obtained from a slaughter  plant specimen, so no history as available other than the cow being labeled as a "cull cow". It was estimated that this pregnancy was approximately 45 days old. It is not a usual to encounter pregnancies in cattle that are severely affected by leucosis, even when the uterus is involved.

Lymphosarcoma pyometra in a cow

Keywords: lymphosarcoma, pyometra, cow, unusual, BLV, leucosis, bovine, uterus, pus

Image size: 1182 x 1756px

An unusual form of pyometra in a cow. Usually, pyometra in cows is due to infection with Arcanobacter pyogenes during the postpartum period. In this case, pyometra was due to bovine leukosis caused by the bovine leukemia virus (BLV). Usually, cows with leucosis in the uterus have multiple nodular disseminated foci of lymphosarcoma; occasionally, large plaques of lymphosarcoma in the myometrium. In this case, there were no typical modules of lymphosarcoma in the uterus. Instead there was a large volume of pus in the uterus, composed entirely of lymphocytes. As is usual, the cow also had disseminated leucosis nodules throughout many of its organs; the spinal canal, heart, liver etc.

Leucosis in a bovine uterus

Keywords: leucosis, bovine, neoplasia, uterus, infertility

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Enzootic bovine leukosis is a result of infection by bovine leukemia virus (BLV). Interestingly, less than 1% of all the cattle infected with this virus actually develop lymphoid sarcomas.  It is characterized by the development of tumors of lymphatic tissues but tumors can be found throughout the body; in this case, the uterus. Although substantial numbers of nodules and diffuse thickening due to leucosis can be found in the uterus, severely affected genital tracts are occasionally found to be pregnant.

Management procedures that transmit blood have the potential to transmit BLV i.e. injections, surgery, tattooing, dehorning etc. It is not clear if biting flies are able to transmit this disease. Although rectal examinations were once incriminated in the spread of BLV, research suggests that under normal conditions this does not occur.

Uterus of a newborn calf.

Keywords: uterus, bovine, calf, caruncles, neonatal, pregnancy

The uterus of a newborn calf. Uterus was floated in water to accentuate anatomical structures. This showed well-formed caruncles at the time of birth. Obviously therefore, pregnancy is not necessary for the development of caruncles.

Normal postpartum bovine uterus.

Keywords: postpartum, suckling, beef, dairy, lochia, involution, uterus, estrus, ovulation

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A normal completely-involuted bovine uterus. Note to the typical Y-shaped structure with a short body and two long horns. In the left ovary, a follicle approximately 2 cm in size can be seen developing. In the contralateral (right) ovary, there appeared to be no significant structures. This is typical of a postpartum reproductive tract in a suckled beef cow.. Cows (milk but not suckled) may ovulate as soon as 10 or 14 days after calving, long before the uterus has even involuted.