Veterinary · Clinical · also MSVE VGO-411, Theriogenology, ARGO
The female reproductive tract, the oestrous cycle and its hormones, heat detection and synchronisation, infertility and pregnancy diagnosis, with emphasis on cows and buffaloes.
In the exams: ICAR AICE-JRF core group 07; ICAR AIEEA-PG 13 (ARGO); Nepal NLEV Theriogenology 8; China clinical paper obstetrics 15; EGEL Plus reproduction and genetics 15
Veterinary gynaecology is the study of the female reproductive system in health and disease: how the tract is built, how hypothalamus, pituitary, ovary and uterus signal to each other, how a cycle becomes a pregnancy, and why females fail to conceive. Reproductive endocrinology is the hormonal half of that story and also the clinician's toolbox, because nearly every synchronisation or infertility treatment is a hormone given at a chosen moment of the cycle. The subject is called theriogenology in North America and Animal Reproduction, Gynaecology and Obstetrics (ARGO) in South Asia, where the Indian Minimum Standards of Veterinary Education place it in course VGO-411.
Reproduction drives every livestock enterprise. A cow or buffalo that does not calve does not milk, and on most farms the largest avoidable loss is quiet: missed heats, badly timed insemination, uterine infection after calving, and buffaloes that stop cycling in the hot months. The practitioner's job is to find which of these is operating and fix it.
This manual is written for a global reader. It treats the cow and the buffalo in most depth, because they carry the most weight in the Indian ICAR examinations, Nepal's licensing examination and the large-animal papers of China, Mexico, South Africa, Australasia and North America, and it compares the ewe, doe, sow, mare, bitch and queen. Hormone doses appear only where they are standard, with species and route, and always with a reminder to check the label. Parturition, dystocia and andrology have their own manuals. Examiners repeatedly ask for cycle and gestation lengths, hormone actions, Ovsynch timing, definitions of repeat breeding, anoestrus and cystic ovarian disease, the classification of uterine disease, the earliest day each pregnancy test works, and herd fertility indices as numbers.
The ovary releases oocytes and secretes hormones. In most species an outer cortex holds the follicles and corpora lutea and an inner medulla carries vessels and nerves. The mare is the exception: her kidney-shaped ovary has the cortex inside and the medulla outside, and ovulation happens only at the ovulation fossa. The cow's ovary is almond-shaped, roughly three to four centimetres long. The buffalo's ovary is smaller, and its corpus luteum (CL) is smaller and often does not protrude, so rectal palpation of buffalo ovaries is less accurate. The sow's ovary looks like a bunch of grapes; the bitch's and queen's lie inside a fat-filled ovarian bursa.
The oviduct has three parts: the infundibulum with its fimbriae, which catches the ovulated oocyte; the ampulla, where fertilisation normally takes place near the ampullary-isthmic junction; and the narrow isthmus, a sperm reservoir that joins the uterus at the utero-tubal junction. Blockage from salpingitis or adhesions of the ovarian bursa causes fertilisation failure in repeat breeders and cannot be felt reliably per rectum; specialist dye-patency tests are used to check it.
The uterus has two horns, a body and the cervix. In ruminants the horns are well developed and curl ventrally and the body is short; the endometrium carries raised caruncles, roughly seventy to one hundred and twenty in the cow, which join fetal cotyledons to form placentomes. The sow's horns are very long and coiled for a litter. The mare has a large uterine body and short horns. The bitch and queen have long straight horns and a short body; the rabbit has two cervices.
The cervix is a firm sphincter, open only at oestrus and birth, and its shape decides how easy insemination is. The cow's cervix usually has three to five annular rings; semen is placed in the uterine body by rectovaginal manipulation. The buffalo's cervix is similar but often narrower and more tortuous. The ewe's rings are tight and offset, so frozen semen is often placed by laparoscopy; the doe's cervix is easier to pass. The sow has no vaginal portion of the cervix and its interdigitating pads lock the boar's corkscrew penis. The mare's cervix has longitudinal folds, no rings, and protrudes into the vagina. The bitch has a long vagina with a dorsal median fold that makes transcervical catheterisation a specialist skill. In the mare, poor vulval conformation lets air and faeces into the vagina and causes endometritis; it is corrected by Caslick's operation. The broad ligament suspends the tract and carries the middle uterine artery, whose fremitus is a pregnancy sign in cattle.
Ruminants have a cotyledonary, epitheliochorial (synepitheliochorial) placenta; antibodies do not cross, so calves depend on colostrum. The mare and sow have a diffuse epitheliochorial placenta, the bitch and queen a zonary endotheliochorial one, and primates a discoid haemochorial one. The mare also forms endometrial cups, which secrete equine chorionic gonadotrophin (eCG).
Congenital anomalies are important because they cannot be treated. The freemartin is a sterile heifer born co-twin to a bull: fused placental vessels carry male factors and XY cells to her (blood chimerism) and her Müllerian ducts fail to develop. More than ninety percent of such heifers are freemartins. The vagina is short and blind; diagnosis is by vaginal length, karyotype or PCR for Y-chromosome material. White heifer disease is segmental aplasia of the Müllerian ducts, linked to the white-coat gene in Shorthorn cattle, with fluid building up in front of the block. Inherited ovarian hypoplasia gives small inactive ovaries and anoestrus.
Puberty is the first ovulation. It occurs when the hypothalamus escapes the strong negative feedback of oestradiol, gonadotrophin-releasing hormone (GnRH) pulse frequency rises, luteinising hormone (LH) pulses follow, and a follicle reaches ovulatory size. Body size and energy matter more than age; heifers are usually bred at about fifty-five to sixty-five percent of mature weight. Kisspeptin neurons are the main gate of GnRH release and integrate steroid feedback with metabolic signals such as leptin, insulin and IGF-I. Buffaloes reach puberty late, commonly at two years or more under village feeding, which delays first calving to three or four years.
LH is released in two modes. Tonic release gives pulses whose frequency progesterone holds down. Surge release follows when rising oestradiol from a dominant follicle crosses a threshold in the absence of progesterone; this positive feedback produces the preovulatory LH surge. Its failure is the central idea behind cystic ovarian disease.
Follicles progress from primordial to primary, secondary and antral stages; only the late stages depend on gonadotrophins. In the two-cell, two-gonadotrophin model, theca interna cells make androgens under LH and granulosa cells convert them to oestradiol with aromatase under follicle-stimulating hormone (FSH). Granulosa cells also secrete inhibin, which suppresses FSH.
In cattle, antral follicles grow in waves. A small FSH rise recruits a cohort; one follicle is selected and becomes dominant at a deviation diameter of about eight to nine millimetres; subordinates regress as FSH falls. If progesterone is high the dominant follicle cannot ovulate and a new wave starts. Most cows have two or three waves per cycle; buffaloes mostly two, with a smaller ovulatory follicle. Buffalo ovaries hold far fewer primordial follicles than cattle ovaries, commonly cited as roughly a tenth, with much atresia, which limits their response to superovulation. Because a hormone's effect depends on the stage of the wave, synchronisation protocols begin by starting a new wave at a known time.
The LH surge causes ovulation in the cow about a day later. The cow and buffalo ovulate after standing oestrus has ended, in the cow about ten to fourteen hours later. The queen, rabbit, camel and ferret are induced ovulators. The bitch ovulates primary oocytes that need two to three days to mature.
The collapsed follicle becomes a corpus haemorrhagicum and then a CL of small (theca-derived) and large (granulosa-derived) luteal cells. In the cow it is functional from about day four or five and regresses around days sixteen to eighteen if there is no pregnancy. Luteolysis in ruminants and the sow is caused by uterine prostaglandin F2-alpha (PGF2α), released in pulses when oxytocin acts on endometrial oxytocin receptors. In ruminants PGF2α passes from the utero-ovarian vein into the ovarian artery by countercurrent exchange; in the mare the route is systemic. Hysterectomy prolongs the CL in ruminants, sows and mares but not in the bitch, whose CL regresses without a uterine signal. The young CL is refractory to PGF2α: about the first five days in the cow and mare, and until about day twelve in the sow. The canine CL needs prolactin in late dioestrus, so dopamine agonists can end it.
The conceptus must stop luteolysis. In cattle and buffaloes the trophoblast secretes interferon-tau around days fifteen to seventeen, suppressing endometrial oxytocin receptors; in sheep the same signal acts around days twelve to thirteen. In the sow, conceptus oestrogen around days eleven to twelve redirects PGF2α into the uterine lumen, and at least about four conceptuses are needed. In the mare the conceptus migrates through the uterus until fixation at about day sixteen, and this mobility prevents luteolysis. The bitch needs no recognition: her luteal phase lasts about as long whether or not she is pregnant.
Photoperiod controls seasonal breeding through pineal melatonin, secreted during darkness. Ewes and most does are short-day breeders that start cycling as nights lengthen; mares and queens are long-day breeders. River buffaloes conceive mostly in months of shortening days and cooler weather, in northern India autumn and winter, with a summer lull in which anoestrus and silent heat are common; both photoperiod and heat stress contribute.
GnRH is a decapeptide released in pulses into the hypophyseal portal system; it releases LH and FSH. Gonadorelin and potent analogues such as buserelin, deslorelin and fertirelin are used to cause an LH surge on demand: to ovulate a dominant follicle, start a new wave, or luteinise a follicular cyst. In cattle gonadorelin is commonly given at 100 micrograms intramuscularly, although labelled doses differ between products — confirm against the product label and your national formulary. Continuous release from an implant first stimulates, then down-regulates the pituitary, which is the basis of reversible contraception with deslorelin in dogs and cats where licensed.
LH and FSH are glycoproteins sharing an alpha subunit. Human chorionic gonadotrophin (hCG) acts like LH and is used to induce ovulation, especially in the mare. Equine chorionic gonadotrophin comes from the endometrial cups between about days forty and one hundred and twenty of equine pregnancy; in other species it has strong FSH-like activity and a long half-life, so one injection at progestogen removal supports follicle growth in anoestrous cows, buffaloes, ewes and does. Prolactin supports lactation and is luteotrophic in the bitch and queen. Oxytocin, a nonapeptide released from the posterior pituitary, causes milk let-down and uterine contraction and in ruminants also comes from the CL. Melatonin translates night length into season.
Oestradiol-17β from the dominant follicle causes oestrous behaviour, the LH surge, cervical mucus and uterine tone. Oestradiol esters are prohibited in food-producing animals in the European Union and restricted elsewhere, so oestradiol-based protocols are legal only where national law allows. Progesterone from the CL, and later from the placenta in species such as the ewe and mare, maintains pregnancy, closes the cervix and suppresses LH pulse frequency; withdrawing it lets a follicle mature, the idea behind progestogen synchronisation. Progestogens in use include progesterone intravaginal devices, flugestone acetate or medroxyprogesterone sponges for small ruminants, norgestomet implants and oral altrenogest for pigs and horses. The sow and doe depend on the CL throughout pregnancy.
PGF2α (natural dinoprost as the tromethamine salt, or analogues such as cloprostenol) lyses a responsive CL. It is used for synchronisation, pyometra, luteal cysts, pregnancy termination and induction of parturition. Common cattle doses are cloprostenol 500 micrograms intramuscularly and dinoprost 25 milligrams intramuscularly — confirm against the product label and your national formulary. Prostaglandins are absorbed through skin and can cause bronchospasm and abortion in people, so pregnant women and asthmatics must not handle them.
Inhibin lowers FSH. Relaxin softens the cervix and pelvic ligaments; in the bitch and queen it comes only from the placenta, making it a pregnancy test. Anti-Müllerian hormone reflects the follicle reserve and predicts superovulatory response. Pregnancy-associated glycoproteins from ruminant binucleate trophoblast cells are the basis of blood and milk pregnancy tests.
The cycle runs from one oestrus to the next: a follicular phase of proestrus and oestrus (receptivity), and a luteal phase of metoestrus and dioestrus. Species may be polyoestrous, seasonally polyoestrous, or, like the bitch, monoestrous.
The cow cycles all year every twenty-one days on average (about eighteen to twenty-four). Standing oestrus averages twelve to eighteen hours, shorter in high yielders and hot weather, and ovulation follows its end by ten to fourteen hours. Metoestrous bleeding, a small bloody discharge one to three days after oestrus, shows that oestrus occurred and says nothing about conception. Progesterone is low at oestrus, rises from about day four, is high from about day eight to sixteen and falls at luteolysis. Zebu cattle show shorter, weaker oestrus, often at night. Gestation is about two hundred and eighty to two hundred and eighty-five days. Dairy cows usually ovulate within three to four weeks of calving, often without visible oestrus.
The river buffalo cycles about every twenty-one days, with a wider range than the cow; oestrus lasts on average about a day with much variation, and ovulation follows its end. Gestation is about three hundred to three hundred and fifteen days in river buffaloes, longer in swamp buffaloes.
Four features cause most buffalo fertility problems. Oestrous signs are weak: homosexual mounting is uncommon, bellowing and vulval swelling are mild, and many heats occur at night or dawn. Ovulation without detected oestrus, silent heat or suboestrus, is one of the commonest causes of apparent anoestrus. Breeding is seasonal, with summer anoestrus made worse by heat stress, since dark skin, sparse hair and few sweat glands make buffaloes heat-sensitive unless they can wallow. Puberty is late and the calving-to-conception interval is long, so calving intervals of sixteen months or more are common. And the small follicle reserve limits superovulation. The response is heat detection with a teaser at night and dawn, confirmation of ovarian status by palpation or ultrasound, cooling and adequate feeding, and timed insemination protocols.
The ewe is a short-day seasonal breeder with a cycle of about sixteen to seventeen days, oestrus of about one to one and a half days with few signs without a ram, and gestation of about one hundred and forty-seven to one hundred and fifty days. Introducing a ram to isolated ewes before the season induces ovulation within days (the ram effect); the first ovulation is often silent. The doe cycles about every twenty-one days, shows clear oestrus of one to two days, carries for about one hundred and fifty days, and is prone to hydrometra (pseudopregnancy).
The sow cycles every twenty-one days all year, with oestrus of two to three days and ovulation about two-thirds of the way through it. Most sows return to oestrus four to seven days after weaning. Gestation is about one hundred and fourteen days, three months, three weeks and three days. Heat causes seasonal infertility in pigs.
The mare is a long-day breeder with a twenty-one-day cycle and an oestrus of five to seven days; she ovulates twenty-four to forty-eight hours before oestrus ends. A spring transitional phase of erratic oestrus and anovulatory follicles precedes the first ovulation. Foal heat occurs about five to twelve days after foaling. Gestation is about three hundred and forty days with a wide range.
In the bitch, proestrus and oestrus each last about nine days on average, with wide variation. Progesterone begins to rise before ovulation as follicles luteinise; ovulation follows the LH surge by about two days, and the oocytes need two to three more days to mature, so the fertile period is roughly four to seven days after the surge. Dioestrus lasts about two months, pregnant or not, followed by anoestrus; the interval between cycles is typically five to twelve months. Gestation is about sixty-three days from ovulation and sixty-five from the LH surge.
The queen is a long-day seasonal breeder and an induced ovulator. Oestrus lasts about a week; if she is not mated, follicles regress and oestrus recurs within a couple of weeks, so an unmated queen may seem to be in heat continuously. An infertile mating gives a pseudopregnancy of about five to six weeks. Gestation is about sixty-three to sixty-five days.
Missed or wrongly identified heats cost more fertility than any disease. The only reliable primary sign in cattle is standing to be mounted. Secondary signs, which also occur outside oestrus, include mounting others, restlessness, bellowing, a swollen vulva, clear stringy mucus, rubbed tail-head hair and a drop in milk. In buffaloes, frequent urination, mild vulval swelling, mucus and bellowing are more useful than mounting. Dried oestrous mucus shows a fern pattern.
Observe at least two or three times daily for twenty to thirty minutes, away from feeding, including early morning and late evening; frequency matters more than duration. The a.m.-p.m. rule times insemination: a cow first seen in heat in the morning is inseminated that evening, one first seen in the evening the next morning, because she ovulates after oestrus ends. Once-daily insemination loses little in many herds. In buffaloes, late-oestrus insemination, repeated after about twelve hours in long heats, is widely advised.
Tail paint or chalk, pressure-activated mount detectors, chin-ball markers on a vasectomised or teaser bull, and activity meters on leg or neck all improve detection; automated activity systems can match good visual observation. Milk progesterone confirms the follicular phase. Palpation and ultrasound confirm oestrus by a toned uterus, a large follicle and no functional CL, and are particularly useful in buffaloes.
Ewes are marked by a ram wearing a harness crayon, with the colour changed each cycle to show returns. Sows are tested by the back-pressure test in the presence of a boar, and stand rigidly when in oestrus. Mares are teased with a stallion; in oestrus they squat, urinate and wink, and ultrasound shows a growing follicle with a cartwheel pattern of endometrial oedema. In the bitch, superficial cells rise to more than about eighty to ninety percent of vaginal epithelial cells at oestrus, and serial serum progesterone marks the LH surge at roughly two nanograms per millilitre and ovulation at roughly four to ten; laboratories and assays differ, so local reference values apply.
The heat detection (submission) rate is the percentage of eligible cows inseminated or seen in heat in a twenty-one-day period; many herds achieve under half. The twenty-one-day pregnancy rate is the heat detection rate multiplied by the conception rate: fifty percent detection and forty percent conception give twenty percent. This one number drives days open more than any other.
Accuracy is checked from intervals between inseminations. Eighteen to twenty-four days is a normal cycle. Thirty-six to forty-eight days means a heat was missed. Intervals below eighteen days, or of twenty-five to thirty-five days, point to insemination outside oestrus, early embryonic death or cysts. Inseminating cows that are not in heat wastes semen and can cause abortion if the cow was pregnant; milk progesterone studies have repeatedly found a share of inseminations made when progesterone was high.
These measures should be calculated every month from the herd's own records. A falling heat detection rate usually points to labour, housing, lameness or negative energy balance; a falling conception rate with a stable detection rate points instead to semen handling, insemination technique, uterine disease or heat stress. Separating the two halves of the pregnancy rate in this way tells the adviser where to look first.
Synchronisation brings a group into oestrus, or to ovulation, at a predictable time, so insemination can be planned and heat detection concentrated or abandoned in favour of timed artificial insemination (TAI). Every programme controls the life of the CL, the stage of the follicular wave, or both.
A single PGF2α injection brings into oestrus within two to five days only animals with a responsive CL, roughly days five to seventeen of the cycle in the cow. A second injection eleven to fourteen days later in cattle catches nearly all cycling animals, because those not responding the first time are then in mid-cycle. Ewes and does in season receive two injections about ten to eleven days apart. Prostaglandin programmes fail in animals with no CL (prepubertal, anoestrous) and abort pregnant animals, so pregnancy status must be known first. The spread of oestrus after injection reflects the stage of the follicular wave at the time of luteolysis: a cow with a large dominant follicle comes into heat within about two days, while one early in a new wave takes four or five. That spread is why prostaglandin-only programmes usually combine injection with a few days of heat detection, and why programmes that also control the wave allow insemination at a fixed time.
Ovsynch uses GnRH on day zero, PGF2α on day seven, a second GnRH on day nine, about fifty-six hours after PGF2α, and TAI about sixteen hours later. The first GnRH ovulates or luteinises a suitable dominant follicle and starts a new wave; PGF2α removes the CL; the second GnRH times ovulation so capacitated sperm are waiting. If the first GnRH is given at 08:00 on a Monday, PGF2α falls at 08:00 the next Monday, the second GnRH at 16:00 on Wednesday, and TAI at 08:00 on Thursday.
In Cosynch, insemination is done with the second GnRH, typically forty-eight to seventy-two hours after PGF2α, saving a handling; conception is often slightly lower in dairy cows. Ovsynch works best when started around days five to twelve, so presynchronisation is used: Presynch gives PGF2α fourteen days apart and starts Ovsynch about twelve days after the second (day twenty-six); G6G and Double-Ovsynch are alternatives. A second PGF2α twenty-four hours after the first improves complete luteolysis. Adding a progesterone device between GnRH and PGF2α prevents early heats and helps anovular cows. The five-day Cosynch with progesterone, used in beef cows and heifers, gives two PGF2α doses because the CL is younger. Heatsynch replaces the second GnRH with oestradiol and is legal only where oestradiol is permitted.
Progestogen programmes mimic a CL: a progesterone device or progestogen implant for about seven to nine days, PGF2α at or before removal, and oestrus two to three days after removal. Progesterone priming can induce cycles in anoestrous animals, especially with eCG at removal. Very long treatments without starting a new wave produce aged persistent follicles of low fertility.
In buffaloes, Ovsynch gives acceptable results in cycling animals in the breeding season but poor results in anoestrous animals and in summer; a progesterone device with PGF2α and eCG at removal, followed by GnRH and TAI, is generally better for them. Results vary with body condition and season.
Out-of-season ewes and does receive progestogen sponges or devices, traditionally for twelve to fourteen days, with eCG at removal; the male effect and melatonin implants advance the season. Gilts receive oral altrenogest for about eighteen days, because the porcine CL is refractory to PGF2α until about day twelve; sows are synchronised by weaning. Mares receive PGF2α at least about five days after ovulation, and hCG or deslorelin to induce ovulation once a follicle of about thirty-five millimetres or more is present with oedema; sixteen hours of light daily from early winter brings the season forward by about two months.
Timed AI fails most often through missed or late injections. A protocol sheet listing each animal and the date and hour of every step, and a fixed start day each week, prevents most errors. Protocol choice follows the herd: Ovsynch for cycling lactating cows, progesterone-containing protocols for heifers, anovular cows and buffaloes, double PGF2α where heat detection is good and drugs are costly.
Dose volume equals dose divided by concentration. A cloprostenol product at 250 micrograms per millilitre, given at 500 micrograms intramuscularly to a cow — confirm against the product label and your national formulary, needs two millilitres. Frequent errors are confusing micrograms with milligrams, a thousand-fold mistake, and confusing the analogue cloprostenol with dinoprost, whose dose is in milligrams. Doses and routes differ between species and products, and several products are licensed for some species and not others, so the label and the national formulary decide what is legal and correct.
The cost of a programme should be judged against the value of a day open and of a pregnancy gained, not against the drug bill alone. In smallholder buffalo systems, a group programme run in the favourable season, with pregnancy diagnosis about two months later, usually gives the best return.
Anoestrus, the absence of observed oestrus, is a sign, not a diagnosis. Physiological anoestrus occurs before puberty, in pregnancy, after calving, in lactation and outside the breeding season. Pathological anoestrus has three main forms. True (anovular) anoestrus: small, smooth ovaries with follicles that do not ovulate, no CL, and low progesterone on two samples about ten days apart. Silent heat (suboestrus): the animal ovulates but shows weak or unseen signs; a CL is present. It dominates in buffaloes, and most anoestrus reported in dairy cows is really undetected oestrus. Anoestrus with a persistent CL: usually secondary to uterine contents such as pyometra or a mummified fetus. Cystic ovarian disease can also present as anoestrus.
The distinction matters because treatments differ completely. PGF2α brings a cow with silent heat into oestrus within days, but it does nothing for a cow with no CL, and progesterone-based treatment is wasted on a cow that is already cycling and simply needs better heat detection. In seasonal species, anoestrus outside the season is normal and is managed by breeding plans rather than treatment.
Negative energy balance in early lactation, low body condition at calving and heavy condition loss, suckling, dystocia, uterine infection and heat stress lengthen the interval to first ovulation. Negative energy balance acts mainly by reducing LH pulse frequency, so follicles grow but do not make enough oestradiol for a surge. Suckling suppresses LH pulses and prolongs anoestrus in beef cows and in buffaloes, which are usually milked with the calf present.
Undernutrition of energy and protein is the main cause of true anoestrus in low-input systems. Phosphorus, copper, cobalt, manganese, iodine and selenium are often implicated, but evidence is stronger for energy than for any single mineral, so supplementation should follow an assessment of the ration. Heat stress lowers oestradiol and weakens oestrus and underlies buffalo summer anoestrus. Other causes include freemartinism, ovarian hypoplasia, chronic disease and parasitism. In the bitch, no oestrus by about two years is primary anoestrus; hypothyroidism is one cause of prolonged anoestrus in dogs.
Record days since calving, heats seen, body condition, feeding, suckling, season and past disease. Examine both ovaries and the uterus per rectum, ideally with ultrasound; if no CL is found, repeat after about ten days or take two progesterone samples ten days apart, because a cycling animal will show a CL at one of them.
Silent heat with a responsive CL is treated with PGF2α and close observation or TAI, with better heat detection as the lasting answer. Anoestrus from undernutrition needs feeding; hormones given to a thin animal on a falling plane of nutrition work poorly. Where nutrition is adequate, a progesterone device for seven to nine days with PGF2α and eCG at removal, followed by observation or TAI, is the most reliable treatment for anovular cows and buffaloes. Restricted suckling or temporary calf separation shortens postpartum anoestrus. Pyometra and mummified fetus are treated with PGF2α. Ewes and does are bred out of season with the male effect, progestogen and eCG; mares with artificial light.
A repeat breeder cycles normally, has no clinically detectable genital abnormality, and fails to conceive after three or more inseminations with fertile semen; some definitions use two. The definition separates repeat breeding from obvious disease such as pyometra, cysts or anoestrus. It is among the commonest reasons for veterinary visits in South Asian dairy herds and for culling worldwide.
The return interval shows when failure happened. A regular return at eighteen to twenty-four days means fertilisation failed or the embryo died before maternal recognition, about days fifteen to seventeen. A late, irregular return means loss after recognition had extended the CL. In high-yielding cows early embryonic loss is at least as important as fertilisation failure.
Repeat breeding is also judged at herd level. If many cows in a herd are repeat breeders, the cause is more likely to be shared, such as semen handling, the inseminator, a bull, nutrition, heat stress or a venereal infection, than a problem of individual cows. If only a few cows are affected, individual causes such as tubal blockage or subclinical endometritis are more likely.
Fertilisation failure arises from blocked oviducts after salpingitis, ovarian bursal adhesions, delayed ovulation (the oocyte arrives after the sperm have aged), and subclinical endometritis that is hostile to sperm. Management causes are common: insemination at the wrong time, poor thawing and handling of semen, wrong deposition site, and inseminating cows not in heat. Bull or semen fertility must be excluded first.
Early embryonic death follows abnormal embryos, a poor uterine environment, and luteal insufficiency, a CL producing too little progesterone in the first week, which impairs embryo elongation and interferon-tau secretion. Heat stress, negative energy balance, excess degradable protein with high blood urea, and oestrogenic feeds or mycotoxins such as zearalenone are associated with lower fertility. Venereal campylobacteriosis (Campylobacter fetus subsp. venerealis) and trichomoniasis (Tritrichomonas foetus) cause early embryonic death with irregular returns in herds using bulls. Bovine viral diarrhoea, bovine herpesvirus 1, leptospirosis and Ureaplasma can also lower conception.
Start with records: services per conception, return intervals, semen, inseminator, season and stage of lactation. Examine per rectum, by vaginoscopy and ultrasound at oestrus and in the luteal phase, and take endometrial cytology by cytobrush or low-volume lavage to detect subclinical endometritis. In naturally mated herds test bulls by preputial sampling.
Correct AI timing, often inseminating later or twice. Give GnRH or hCG at AI where delayed ovulation is suspected. GnRH, hCG or progesterone five to seven days after AI supports the CL where luteal insufficiency is suspected; trial gains are modest and inconsistent. Treat subclinical endometritis with PGF2α when a CL is present, or with licensed intrauterine products where law allows, respecting milk withdrawal. Many empirical intrauterine infusions have weak evidence. Correct nutrition and heat stress at herd level. A cow that still fails may become an embryo recipient or be culled, judged on yield and age. Records of every treatment and its outcome let the practice see which interventions actually work in its own herds.
Cystic ovarian disease (COD) in cattle is the presence of follicle-like structures larger than an ovulatory follicle that persist without ovulating and without a functional CL. The classical definition is more than twenty-five millimetres, persisting more than ten days; many texts now accept about twenty millimetres. Definitions vary, so state the one used.
A follicular cyst has a thin wall under about three millimetres and low progesterone, and may secrete oestradiol. A luteal cyst has a thick luteinised wall of three millimetres or more and secretes progesterone. A cystic CL is different: a normal CL formed after ovulation with a fluid cavity; it produces progesterone, does not disturb the cycle and needs no treatment.
The central defect is failure of the LH surge: the dominant follicle makes oestradiol but the hypothalamus does not respond, so the follicle keeps growing. Intermediate progesterone, negative energy balance with low insulin and IGF-I, stress and postpartum uterine infection lower hypothalamic sensitivity. Most cysts arise in the first two months after calving, in high yielders and older cows; many early cysts regress spontaneously. Buffaloes develop cysts less often than dairy cows.
In modern dairy cows the commonest presentation is anoestrus. The classical nymphomaniac form, linked to oestrogen-secreting follicular cysts, shows frequent or persistent oestrus, bull-like behaviour and relaxed sacrosciatic ligaments with a raised tail-head (the sterility hump). Palpation finds a large fluctuating structure but cannot reliably separate follicular from luteal cysts. Ultrasound measures size and wall thickness and looks for a CL; milk or plasma progesterone separates the types, roughly below one nanogram per millilitre for follicular cysts, with laboratory-specific thresholds.
A single examination cannot prove persistence. Ideally the structure is seen twice several days apart, with no CL at either examination, but in practice many cows are treated on one finding supported by ultrasound and progesterone. It is also important not to mistake a large preovulatory follicle in a cow near oestrus, or a cystic CL, for a cyst: a cow in oestrus has a toned uterus and clear mucus, and a cystic CL has a thick luteal rim and high progesterone. Herd records showing many cysts should prompt a review of transition-cow nutrition and uterine disease rather than more hormones.
GnRH or an analogue is the standard first treatment for follicular cysts: it releases LH, luteinises the cyst wall and often ovulates other follicles, and oestrus usually follows in about eighteen to twenty-three days. Many clinicians give PGF2α about seven to fourteen days after GnRH, or use Ovsynch for a known AI date. hCG is used similarly. A progesterone device for seven to nine days with PGF2α at removal resets hypothalamic sensitivity so the next follicle can trigger a surge. Luteal cysts are treated with PGF2α. Manual rupture per rectum is discouraged: it can cause haemorrhage and ovario-bursal adhesions and does not correct the cause. Prevention rests on good transition management and prompt treatment of uterine disease.
Sows develop multiple cysts causing anoestrus or irregular cycles. Mares do not have bovine-type COD; they have anovulatory haemorrhagic follicles and harmless fossa or paraovarian cysts. In the bitch follicular cysts prolong oestrus, and persistent oestrogen can suppress the bone marrow, causing anaemia and thrombocytopenia; ovariohysterectomy is usual. Queens with cysts show persistent oestrus.
Almost every cow's uterus is contaminated with bacteria after calving; disease develops when defence fails. Risk factors are dystocia, twins, retained fetal membranes, stillbirth, milk fever, negative energy balance and poor hygiene. Trueperella pyogenes, Escherichia coli, Fusobacterium necrophorum and Prevotella species are the main bacteria, and T. pyogenes is most linked with persistent endometritis.
A widely used classification separates: puerperal metritis within about twenty-one days, usually the first ten, with an enlarged uterus, fetid red-brown discharge and systemic illness such as fever above 39.5 °C; clinical metritis, the same without systemic signs; clinical endometritis, a purulent discharge from about three weeks or mucopurulent after about four, without systemic illness; subclinical endometritis, no discharge but raised neutrophils on endometrial cytology, for example more than about eighteen percent at three to five weeks (thresholds vary); and pyometra, pus in the uterus with a persistent CL. Endometritis is a major cause of lower conception and longer days open.
Palpating uterine size is unreliable. The discharge is examined by gloved hand, vaginoscope or a device that draws mucus from the cranial vagina and is scored for character and smell; subclinical endometritis needs cytology, or ultrasound showing intraluminal fluid.
Puerperal metritis is systemic and is treated with systemic antimicrobials chosen under local law, prudent use and withdrawal periods, with anti-inflammatories and support. Clinical endometritis in a cow with a CL is often treated with PGF2α, which induces oestrus and improves uterine defence; its value without a CL is debated. Licensed intrauterine antimicrobials exist in some countries and not in others. Antiseptic infusions such as povidone-iodine irritate the endometrium and are no longer favoured. Involution is usually complete by about forty days, which informs the voluntary waiting period. In buffaloes endometritis is a leading cause of repeat breeding, diagnosed and treated on the same principles. Delayed postpartum cyclicity in buffaloes also delays the protective effect of oestrus on the uterus. Prevention in both species depends on hygiene at calving, careful obstetric assistance, prompt treatment of retained membranes and milk fever, and good transition feeding.
In the mare, endometritis is the main cause of subfertility. Breeding always causes a transient inflammation that a normal mare clears within a day or two; older, multiparous mares with poor drainage or conformation develop persistent breeding-induced endometritis, managed by uterine lavage a few hours after breeding and oxytocin. Bacterial causes include Streptococcus equi subsp. zooepidemicus, E. coli, Pseudomonas aeruginosa and Klebsiella pneumoniae. Contagious equine metritis, caused by Taylorella equigenitalis, is notifiable in many countries and controlled by pre-season swabbing. Endometrial biopsy is graded by the Kenney-Doig system into categories I, IIA, IIB and III.
In the bitch, repeated progesterone exposure in dioestrus causes cystic endometrial hyperplasia, and ascending bacteria, most often E. coli, cause pyometra, typically within a few weeks to about two months after oestrus in middle-aged bitches: polydipsia, polyuria, depression, vomiting and discharge if the cervix is open. Closed-cervix pyometra risks rupture and sepsis. Ovariohysterectomy after stabilisation is the treatment of choice; aglepristone with or without PGF2α is used in selected breeding bitches with an open cervix, where licensed. Queens get pyometra less often because they ovulate only when mated.
Infertility is a temporary inability to reproduce; sterility is permanent. Herd infertility is judged from records. The calving interval equals days open plus gestation; a traditional dairy target is about twelve to thirteen months, though many high-yielding herds accept longer. For buffaloes about thirteen to fourteen months is a common goal, while field averages are often sixteen months or more. Days open is calving to conception. The voluntary waiting period, commonly about forty-five to sixty days in dairy cows, is the time after calving when the farmer chooses not to inseminate. Services per conception equals inseminations divided by pregnancies, with under about 1.5 to 2 regarded as good; the conception rate is its reciprocal as a percentage, and first-service conception rate is watched separately. Heat detection rate, twenty-one-day pregnancy rate, age at first calving and culling for infertility complete the picture. Targets depend on system and economics, so trends within a herd matter most.
Management causes are the largest group: poor heat detection, wrong AI timing, poor semen handling and technique, long waiting periods, and failure to examine cows not seen in heat. Nutritional causes include low condition and heavy condition loss, negative energy balance, excess degradable protein and locally known mineral deficiencies. Environmental causes include heat stress, poor housing and lameness, which suppresses oestrous expression. Periparturient disease has knock-on effects for weeks. Infectious causes need laboratory diagnosis and many are zoonotic or notifiable: brucellosis, leptospirosis, bovine herpesvirus 1, bovine viral diarrhoea, neosporosis, venereal campylobacteriosis and trichomoniasis. Congenital causes include freemartinism, white heifer disease and ovarian hypoplasia. A subfertile bull in a naturally mated herd can look like a female problem.
At cow level, problem animals are sorted into three groups, each with its own work-up: not seen in heat (anoestrus, silent heat, cysts, pregnancy); bred but not conceiving (repeat breeding, subclinical endometritis); and abnormal discharge (metritis, endometritis, pyometra).
Buffalo infertility is dominated by late puberty, long postpartum anoestrus, silent heat, summer anoestrus, poor heat detection, endometritis and, above all, undernutrition: village buffaloes often eat crop residues with little energy concentrate or minerals. Heat stress is severe without a wallow or shade.
Programmes that consistently help combine several steps: feeding heifers to a target weight; calving in good condition with controlled suckling; heat detection with a teaser bull at night and dawn; examining animals not seen in heat by about sixty to ninety days after calving; shade, wallowing, fans and sprinklers in summer; mineral mixtures where deficiency is known; and hormonal protocols matched to season and ovarian status, followed by pregnancy diagnosis. For both species, the most effective single measure is a regular herd fertility visit every two to four weeks, examining postpartum, not-seen-in-heat, pregnancy-check and discharging animals and reviewing indices each time. Economic decisions, such as how long to keep treating a cow before culling, depend on local milk prices, replacement costs and the value of a day open.
Early diagnosis lets open females be re-bred or culled, detects twins and loss, and prevents abortifacient drugs being given to pregnant animals. Early positives should be rechecked because some embryos and fetuses are lost.
Non-return to oestrus is unreliable, because anoestrus, silent heat and poor detection look the same. Milk or plasma progesterone at about twenty-one to twenty-four days after insemination is a good negative test: low progesterone means not pregnant with high accuracy, while high progesterone only shows a CL. In the bitch progesterone is useless, because pregnant and non-pregnant dioestrous values are similar.
Pregnancy-associated glycoproteins (PAG) in blood or milk diagnose pregnancy in cattle, buffaloes, sheep and goats from about four weeks, but persist for weeks after calving, so testing too soon after the last calving gives false positives; the minimum interval depends on the test. Oestrone sulphate from the fetoplacental unit is used in pigs and mares. eCG identifies pregnant mares at roughly days forty to one hundred and twenty but stays positive if the conceptus dies after the cups form.
Transrectal palpation remains the most widely used method. In the cow, horn asymmetry with fluctuation, the fetal membrane slip and the amniotic vesicle are felt from about thirty-five to forty days by experienced examiners; placentomes from about the third month; and fremitus of the middle uterine artery from about three to four months. From about the fifth month the uterus sinks into the abdomen. In buffaloes the tract is often deeper and more coiled, and signs may be felt slightly later.
Transrectal ultrasonography with a probe of about five to seven and a half megahertz shows the embryo with a heartbeat from about twenty-six to thirty days, and diagnosis from about day twenty-eight is reliable in skilled hands. It also detects twins, embryonic death and ovarian and uterine pathology, and sexes the fetus from the genital tubercle at about fifty-five to seventy days. Its accuracy and earlier result make it the method of choice where equipment and skill are available, and the ovaries can be checked for a CL at the same visit. Gentle technique matters, because rough handling of the amniotic vesicle in early pregnancy has been blamed for occasional losses.
Ewes and does are scanned transabdominally from about forty to forty-five days, with fetal counting so that twin- and triplet-bearing ewes can be fed accordingly; transrectal scanning works from about twenty-five to thirty days. In does, hydrometra shows as fluid without fetuses or placentomes and is treated with PGF2α. Sows are diagnosed by A-mode or Doppler ultrasound from about thirty days, real-time ultrasound from about twenty-four days, or oestrone sulphate from the fourth week.
In the mare the embryonic vesicle is visible by transrectal ultrasound from about eleven to fourteen days, and an examination at fourteen to sixteen days is essential to find twins and crush one before fixation at about day sixteen. In the bitch, ultrasound shows gestational sacs from about twenty to twenty-five days after the LH surge, relaxin becomes detectable from about the fourth week, and radiography counts puppies after about forty-two to forty-five days. Queens are diagnosed by ultrasound from about the third week, palpation at three to four weeks and radiography after about day forty.
Learn the tables first: cycle length, oestrus duration, time of ovulation and gestation length for each species, and the day each pregnancy test first works. Then learn one mechanism properly, the follicular wave and the CL, because synchronisation, cysts and anoestrus all make sense from it. Practise rectal palpation on slaughterhouse tracts and live cows until you can find a CL on a buffalo ovary. Write out the Ovsynch timetable from memory with dates and hours, and work at least ten herd-index calculations (calving interval, services per conception, pregnancy rate) so they are automatic in the exam hall.
Your daily work is the problem cow: not seen in heat, bred repeatedly, or discharging. Examine by rectum and ultrasound, decide whether she is anovular, cycling silently, cystic or has endometritis, and treat accordingly rather than by habit. Set up a fixed-day herd fertility visit, keep a protocol sheet for every timed AI group, and calculate the herd's heat detection and pregnancy rates each month. In buffalo areas, time synchronisation campaigns to the breeding season, push for summer cooling and mineral supply, and check that farmers understand the timing of each injection. Always confirm pregnancy status before any PGF2α.
At this stage you design programmes rather than treat cows. You set protocol choices for a district or a large dairy company, audit AI technicians, and interpret herd data to show owners that heat detection and transition-cow nutrition, not drugs, drive fertility. You weigh the cost of hormones against the value of a day open and decide when culling is cheaper than treatment. You also judge the legality of each hormone and intrauterine product in your country, keep withdrawal periods, and train younger vets to diagnose by ultrasound and cytology rather than by feel alone.
Research questions here are open: why buffaloes and high-yielding cows show weak oestrus, how negative energy balance signals through kisspeptin to GnRH, how to reduce embryonic loss between days 15 and 60, how to diagnose and treat subclinical endometritis without antimicrobial overuse, and which synchronisation designs suit smallholder buffaloes economically. A senior researcher designs controlled field trials with adequate numbers, uses progesterone and ultrasound to classify cows before treatment, reports pregnancy per AI with confidence intervals, and separates statistical from economic significance. Work across species and countries so results are not confined to one breed or climate.
This manual does not give doses beyond the three standard cattle doses of cloprostenol, dinoprost and gonadorelin, because labelled doses of GnRH analogues, hCG, eCG, progesterone devices, altrenogest, melatonin and canine and equine products differ between products and countries; use the label. It gives ranges, not single values, for oestrus duration, the day each pregnancy test first works and cyst definitions, because textbooks differ. It does not cover camelids, yaks, mithun, deer or laboratory species; embryo transfer, OPU-IVF, sexed semen and male reproduction (covered in the andrology manual); parturition, dystocia and retained placenta (covered in the obstetrics manual); or national rules on intrauterine antimicrobials and oestradiol, which the reader must check locally. Evidence for mineral supplementation and for many repeat-breeder treatments is summarised only qualitatively.
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