POSTPARTUM DISORDERS AFFECTING REPRODUCTION
The postpartum period of the cow presents the dairy producer with many management challenges. Postpartum dairy cows may have one
or more reproductive disorders that delay or prevent the start of rebreeding. Delays in rebreeding beyond approximately 60 to 80 days
after calving greatly reduce reproductive efficiency of the herd and thus greatly increase costs of production.
Cystic Ovarian Disease
Dystocia
Metritis and Endometritis
Pyometra
Retained Placenta
Short Estrous Cycles
Silent Heat
Static Ovaries
Cystic Ovarian Disease
Ovarian cysts are follicular structures at least 2.5 cm in diameter, present 10 or more days on the ovary when
there is no functional corpus luteum present. The incidence of ovarian cysts ranges from 5 to 20% in most herds,
with just over one third of the cysts reported to occur within a few weeks after calving. The cows with cysts
show a much earlier follicular development, delayed follicular rupture, and a
longer interval to first ovulation. Cystic ovaries are usually associated with
a lack of observable estrus (anestrus); however,
erratic estrus and nymphomania may also be seen.
Ovarian cysts can be classified as either follicular
cysts or luteal cysts.
Causes: Several factors influence cystic ovaries in
cattle.
Milk production has been implicated as a cause of ovarian cysts, because there is a greater
occurrence in high milk producers. It must be emphasized, however, that it is still unclear
whether the increased milk production leads to ovarian cysts, or whether the imbalanced
hormonal environment produced by the cysts leads to the increased milk production.
Age and parity are also factors influencing ovarian cysts. There is a much greater occurrence of ovarian cysts in
mature cattle (39% incidence) than in first calf heifers (11% incidence).
Breed of cattle (genetic influence) has been shown to affect the occurrence of cystic ovaries. It has long been
reported that cyst formation is a heritable trait. Beef cattle rarely are affected with ovarian cysts, and in a
Swedish study, through sire selection and a controlled breeding program, the national incidence of ovarian cysts
in dairy cattle was decreased from 10 to 3% over a 20 year period.
Seasonal stresses may also play a role in the occurrence of ovarian cysts. Studies report that fall-freshened
cattle have an approximately 5% greater chance of producing ovarian cysts than do their spring-freshened
herdmates.
Treatment Treatments have changed over time. Manual rupture during rectal palpation has been used with only
limited success. It also may, in rare cases, cause excessive bleeding from the site of rupture and scar tissue
formation around the ovary.
The most successful treatment of follicular cysts is the use of hormones that cause ovulation. Human chorionic
gonadotropin (hCG) and, more recently, gonadotropin releasing hormone (GnRH) have been administered with up
to an 80% response to the treatment and up to a 60% conception rate at the resulting ovulation. Luteal cysts can
be effectively treated with prostaglandins which cause regression of the luteal tissue.
Dystocia
Dystocia is difficult parturition, usually with a prolonged labour or delivery that requires assistance. The incidence of dystocia within a
herd averages about 14%, but a heifer is three times more likely to ha.e difficult calving than a mature cow.
Causes: Fetopelvic Disproportion: By far the most common cause of dystocia is a calf larger than the birth canal. This means that either
the birth canal of the dam is too small, the calf is too large, or both occur simultaneously. Quite a variety of factors may contribute to
the small size of the dam and to the large size of the fetus.
A heifer bred too young, on a low plane of nutrition or affected by parasitism or disease, will have a less than ideal growth rate, and her
body size and weight may not be enough to accommodate the size of the fetus during calving. Another size problem is caused by the
overfeeding of a growing heifer, which results in the deposition of fat in the tissues surrounding the vagina. This fat can narrow the
pelvic canal.
Structural abnormalities of the dam's birth canal may also interfere with the ease of calving. A persistent or overdeveloped hymenal ring,
a double cervix, or tissue band remnants of fetal structures in the cervix or vagina may all present obstacles to the passage of the calf.
Incomplete relaxation of the ligaments or incomplete dilation of the cervix also halts delivery. Scar tissue strictures or fibrous adhesions
which may be remnants of the healing of severe inflammation or traumatic injury from previous calvings may narrow all or parts of the
birth canal. There may also be deformities, fractures, or dislocations of the pelvic bones, which can decrease the size of the pelvic inlet
and cause dystocia.
Sire selection can also play a role in the future ease of calving. Small females are too often bred to much larger bulls in hopes of
attaining large calves of improved genetic stock. Unfortunately, these small dams have small birth canals which cannot accommodate
the huge calves.
There are several abnormal conditions which produce oversized calves and thus dystocia. Malformations may include missing parts,
duplication of parts, or abnormal size, shape, form, or consistency of fetal parts. Some of these conditions, like rigid or contorted joints,
hydrocephalus(enlarged, fluid-filled head), and fused twins, have genetic causes.
Fetal death can lead to a dystocia because the fetus plays a critical role in parturition. Umbilical cord rupture or compression, or trauma
to the fetus, can cause an enlarged fetus because of improper circulation and accumulation of blood and fluids within certain parts of the
fetus. The fetus may bloat or become distended with gas after death, and the increased size may prevent its easy delivery.
Presentation and Posture of Calf The presentation and posture of the calf are also important for normal delivery. Malpresentation or
malposture may create the effect of a too small birth canal. There are several ways a calf can be aligned within the dam. The proper
positioning is chest toward the uterine floor, nose lying between the forelegs, and forelegs pointed toward the dam's tail. This position
provides the smoothest, cleanest delivery. A malpresented fetus is one that is either presented sideways, backwards, or upside down. A
malpostured fetus may have abnormal flexion or extension of the head, neck, shoulder, foreleg, hindleg, or hip, all of which prevent
easy delivery. Such difficulties are even more severe when twins are present.
Although fetopelvic disproportion and malpresentation constitute the major causes of dystocia, there are several uterine conditions
which can create problems as well.
Uterine Conditions Ineffective labour is a term describing weakness or incoordination of contractions. Any condition which produces an
unusually distended uterus, such as twin pregnancy or an exceptionally large fetus, has a tendency to weaken the force of contractions.
Other causes of weakened muscle contractions may be an inability of the uterus to respond to the stimulus of the hormones oxytocin
and estrogen, a lack of calcium caused by milk fever, and a number of metabolic disorders such as ketosis, nutritional deficiencies,
toxemia, and septicemia.
Incoordination of muscle contractions also leads to dystocia. Distension of the vagina causes a reflex release of oxytocin. The oxytocin
causes increased intensity of uterine contractions. In the case of an impacted fetus within the vagina, contractions and straining
increase, and the coordinated wave-like character of the contractions may be lost. Assisting the delivery by manual manipulation in this
case may add more stimulus to nerve receptors and increase spasms.
Displacement of the uterus occurs when the anterior part of the pregnant horn which has grown out beyond its ligamental attachments
rolls up over the small non-pregnant horn, putting a giant twist in its longitudinal axis. Lack of exercise, weak abdominal muscles, or
anything increasing the mobility of the uterus (a fall, walking up a slope, sudden head butt in the side, or low levels of fluid within the
uterus which puts the moving fetus in close contact with the uterine wall) may cause uterine torsion.
Dystocia may also be caused by uterine rupture. Uterine rupture may occur due to uterine torsion with increased calf movement or an
exceptionally large or malformed fetus or, during assisted delivery, due to careless use of instruments. Uterine rupture occurs rarely,
but when it does, any or all of the fetus may slip out into the abdominal cavity. Effective uterine contractions are lost, and the calf may
not be deliverable without assistance.
Dystocia is associated with delayed uterine involution due to tissue trauma and repair. There is a much higher incidence of endometritis
after dystocia due to the introduction of contaminated hands or instruments into the birth canal. Trauma to the birth canal from impacted
calves, instruments, or traction can also lead to scarring and adhesions which can be the cause of dystocia upon subsequent calvings.
The best advice is to prevent dystocia with a comprehensive program of proper nutrition, sire selection, and breeding heifers at the
proper age and weight.
Treatment The treatment of dystocia can begin before calving starts. Close observation of suspected problem
calvings and of those animals carrying twins is a good practice. So is providing a clean dry area for calving.
Sanitation is also very important at this time. Once calving begins, the next step is to manually correct faulty calf
alignment, moistening the birth canal with a lubricant if the walls are not wet and slippery. Traction should be
used if necessary, but the area around the vulva should be cleaned and hands, instruments, and chains should be
scrubbed or soaked in dilute iodine to prevent contamination of the birth canal. Care should be taken to prevent
tearing of the lining of the birth canal during traction.
Cesarean section can be performed when the calf is still alive and natural calving is not possible. The surgery can
be performed with the dam either standing or laying down.
Fetotomy, the process of cutting and removing a dead fetus from the uterus, can be performed when the dead calf
cannot be passed naturally. Care must be taken with the instruments to prevent injury to or rupture of the uterus.
Metritis and Endometritis Metritis and endometritis are both infections of the uterus. Metritis refers to inflammation of the entire uterine
wall, while endometritis is limited to inflammation of the glandular layer of the uterus. The classic
signs of severe metritis or endometritis include the presence of palpable fluid in the uterus after 8 to
10 days postpartum, vulvar discharge containing pus possibly continuing past 15 to 20 days
postpartum, depression, lack of appetite, decreased milk production, and fever. Metritis and
endometritis may also appear in less severe chronic form with little or no fluid accumulation in the
uterus and little or no discharge. The animal may not appear depressed or feverish, but milk
production may still be decreased.
Metritis and endometritis can lead to greatly reduced fertility and prolong the interval to involution
and first ovulation. Mild infections may only delay involution a week or so, but serious metritis or endometritis may extend these
intervals 20 or more days and increase the calving interval 16 to 36 days. These delays may be due to interference with the normal
feedback mechanisms and hormones controlling the estrous cycle.
Metritis and endometritis can delay conception after ovulation by direct damage of the ova or sperm by bacterial or fungal toxins
produced by the infection. Studies show that bacteria may be indirectly responsible for early embryonic losses by producing an
environment which prevents the implantation of a fertilized embryo. Some gram negative bacteria produce endotoxins which may
stimulate the uterine synthesis and release of prostaglandins; this causes the regression of the corpus luteum. And finally, metritis and
endometritis may permanently reduce fertility by the formation of scar tissue and adhesions that may block oviduct passage of ova or
may prevent implantation of the embryo. Studies show a wide variation, from 9 to 26%, in the incidence of metritis and endometritis in
all postpartum cows. Some reports show the incidence artificially high because they do not take into account that 20 to 95% of all
normal postpartum cows experience bacterial contamination of the uterus. The mere presence of bacterial organisms within the uterus
does not necessarily indicate that metritis or endometritis is present, since some bacterial contamination will be part of the normal
involution process, nor does the absence of bacteria from the uterus necessarily mean that infection does not exist.
Causes: The causes of metritis and endometritis are many. The most common cause of metritis and endometritis is invasion of the
reproductive tract by bacterial or fungal organisms. Some of the most common organisms are Escherichia coli, Staphylococcus,
Streptococcus, Pseudomonas, Klebsiella, Lactobacillus, and Corynebacterium pyogenes. The uterus and upper birth canal are free of
contamination prior to calving, but calving is not a sanitary process. These organisms are present in the feces, bedding, or on the hands,
chains, or instruments used to deliver the calf. The process of birth opens the cervix and creates an avenue for bacterial or fungal
ascent to the uterus. This is coupled with a stress-induced reduction in the dam's ability to fight infection.
Metritis and endometritis can also be caused by systemic infections such as Infectious Bovine Rhinotracheitis and Bovine Diarrhea Virus,
two viral diseases, or Leptospirosis, a bacterial disease. Venereal transmission of diseases such as Vibriosis or Trichomoniasis from the
bull to the female during natural service can also lead to uterine infection. However, with the use of regular vaccination programs and
artificial insemination, these causes of metritis and endometritis are now less common.
There are several factors influencing the incidence of metritis and endometritis. These include the age and parity of the female,
difficulties in calving, retention of the placenta, and irritation of the uterine lining.
The age and parity of the female are important factors in the incidence of uterine infection. An older female has a lessened ability to
fight infection, coupled with the natural reduction in tone of the cervical closure that comes with each delivery. This provides a suitable
environment for bacterial ascent to the uterus.
Metritis and endometritis occur with greater frequency after a difficult calving due to the possibility of tearing the uterine lining and the
increased chance of uterine contamination associated with an assisted delivery.
The incidence of metritis and endometritis increases to a high of 80% in those cows retaining fetal membranes for greater than 12 hours.
(If the placenta is retained only 7 to 12 hours, the incidence is only 30%.) The protruding parts of the placenta serve as a favourable
environment for continued bacterial contamination and growth and provide an increased ease of ascent of organisms up to the uterus
through the open cervix. A reduced ability to fight infection also results from the stresses associated with the retained placenta.
A management practice which can increase the incidence of metritis and endometritis is uterine infusions. Uterine infusions of
concentrated Lugol's solution or certain antibiotics such as oxytetracycline can cause irritation and necrosis of the uterine lining. A
necrotic uterine lining provides an ideal environment for bacterial or fungal growth. Infusions can be responsible for delayed rebreeding;
therefore, proper dosage and timing of treatment is important. Less than 10% of all postpartum cows and heifers should require uterine
infusions. It is imperative that dairy producers consult with veterinarians prior to using uterine infusions.
Prevention is mostly common sense: providing a clean, stress free environment. A routine vaccination program, balanced rations, and
adequate housing with comfortable and sanitary maternity areas are important. It is wise to establish a post-calving examination routine,
with good record keeping and communication with a veterinarian.
Treatment When metritis and endometritis occur, treatment may be needed. Intrauterine infusion of antibacterials,
such as antibiotics, sulfonamides, and/or mild disinfectant solutions, is the most common treatment for metritis
and endometritis. However, it is important to consult a veterinarian on the type of therapy, because many of the
organisms which cause infection are resistant to certain antibiotics.
The concentration of the infusion solution is also important. A very concentrated solution may irritate the uterine
lining and compound the problem, whereas very dilute concentrations may be ineffective or may only kill off
certain organisms and provide an excellent environment for opportunistic bacterial takeover. Studies have shown
that routine intrauterine infusion of antibiotics fails to produce an improvement in fertility and may act to disrupt
the normal processes involved in fighting infection and in uterine repair.
A treatment gaining favour is the use of prostaglandins in the treatment of metritis and endometritis. This
treatment is most beneficial when a functional corpus luteum is present on the ovary, and, therefore, after
ovulation has taken place. The prostaglandins causes regression of the corpus luteum in 2 to 4 days. The induced
heat that follows increases the ability of the uterus to fight infection. Uterine contractions during heat aid in the
expulsion of pus, fluid, and debris that may be present within the uterus. Again, this treatment is only of value in
those animals with a functional corpus luteum.
Injectable antibiotics are beneficial because they can be regulated in proper concentrations more readily than
uterine infusions. Unfortunately, only a limited number of drugs or drug combinations are available to use on
lactating dairy animals. Also, there are milk and slaughter withdrawal times after treatment, so it is essential to
consult a veterinarian before beginning treatment.
Pyometra Pyometra is a severe uterine infection. Like metritis and endometritis, pyometra has the potential to greatly reduce fertility.
Because the condition often does not manifest itself until after 28 days postpartum, there will be an obvious lengthening of the calving
interval. Pyometra tends to create the same problems as metritis and endometritis, a thickening and scarring of the uterine wall and the
presence of pus and debris in the uterus which retards the normal postpartum recovery process.
Causes: Pyometra is usually caused by Corynebacterium pyogenes when the uterus is under the
influence of progesterone (produced by the corpus luteum). The corpus luteum present on the
ovary is the result of a postpartum ovulation; therefore, cases of pyometra rarely occur before 21
to 28 days postpartum and more commonly are noticed from 36 to 56 days postpartum. The
progesterone produced by the corpus luteum decreases the ability of the immune system to
respond and thus increases the susceptibility to uterine infection. This corpus luteum is retained
on the ovary until the condition is remedied. As long as the functional corpus luteum is present,
the cow cannot return to estrus. Pyometra is characterized by a grossly distended, pus filled
uterus, with or without a vulvar discharge containing pus.
The incidence of pyometra is about 2 to 6% in postpartum cows. Factors that would increase the
incidence of metritis or endometritis would effect pyometra in the same way. An annual incidence
of pyometra in the herd of greater than 7% indicates that reproductive management techniques
need to be improved.
Treatment Pyometra is best treated, like metritis and endometritis with a functional corpus luteum, by administration of prostaglandins
with or without infusion of the uterus. If left untreated, pyometra can continue indefinitely.