• Anestrus is considered a problem when cows are not seen in heat.
• Failure to observe heat and heat detection must always be ruled out as the primary problem. Review heat detection procedures and heat detection efficiency with the producer.
• Pregnancy can be a prominent cause of anestrus and must always be a always be a prime ruleout before anything else. Pregnancy is often the # 1 cause of cows not being seen in heat.
• Rule out true anestrus by palpating the ovaries

• A freemartin is a heifer born twin to bull. 90% are sterile
• It is caused by a chimeric condition where hematopoetic cells intermingle in utero between the fetuses. This results in XX and XY cells present in a freemartin.
• Partial expression of TDF (testicular determining factor) from male Y chromosome inhibits the female gonad.
• MIF (Müllerian  inhibition factor) from the male cells prevents Müllerian duct formation, so no uterus forms.

Clinical Signs

• These animals often have a masculine steer-like appearance.
• They may have a small vulva and long vulvar hairs.
• Usually the external signs of a freemartin are noticed by the producer, so the ones you will examine as anestrus heifers will probably have normal external signs.

Diagnosis

• The 'test tube test' checks the vaginal depth by using a test tube.
• In normal animals you can insert a test tube 12-18 cm. In abnormal heifers the tube will only go about 7.5 cm into the vagina. This test is only for young heifers, and age can play a big role in how deep the vagina is.
• If they are old enough, palpation is the way to go. These animals have no ovaries, uterus, or vagina.
• A karyotype checks for the XX and XY cell mixture in the blood. It can be run in animals of any age, and may be cost effective if the cost of raising the animal to maturity is considered.

• This is a rare condition when one or both ovaries are absent.
• It is caused when the gonadal ridge does not form correctly.
• Palpation is the best diagnostic method.
• There may be partial aplasia, when only one ovary does not form.

• In ovarian hypoplasia, one or both ovaries are smaller than normal.
• This is a recessive trait in the Swedish Highland breed and is caused by a single autosomal recessive gene with incomplete penetration.
• You must ruleout true anestrus.
• Again, there may be partial hypoplasia with this condition.

Seasonal Anestrus 403-

• The is some evidence that daylight length (photoperiod) influences fertility in Brahman breeds, but there is no seasonal anestrus in cattle.
• Summer heat stress, when the THI (temperature humidity index) combined effects of heat and humidity produce a high "apparent temperature". If you compare estrus duration at 33.5⁰ vs 18.2⁰ C, then the estrous cycle is longer and the estrus duration is shorter and estrus intensity is less.
• Anestrus may not really occur here, but since estrus is harder to detect, it may appear so.

Nutritional anestrus (Tables )423-427

• Nutritional anestrus in the most common problem in beef cows. Producers often try to get by on as little feed as possible to their cows.
• Remember the beef producers' goals is to produce and wean as many pounds of calves each year as possible.
• Postpartum nutrition
  • In the postpartum cow, lactation causes a negative energy balance. This is even more so in first calf heifers which are also still growing. Therefore, heifers, with the demands of lactation, a negative energy balance and still trying to grow, are affected most by nutritional anestrus. 
  • It takes cows 90 days to attain a 60% conception rate, whereas it takes heifers 110 days. This is primarily because the heifers are not cycling. 
  • By examining these tables you can see that a cow will cycle back sooner than a heifer and therefore become pregnant sooner after parturition.
• By feeding cows after they calve, you cannot expect to improve the number cycling. 
• Feeding pre-partum is the best way to assure early return to cyclicity in beef cows. 
• By providing good pre-partum nutrition, you maintain adequate pre-partum condition, so the stress of postpartum lactation produces a shorter duration of negative energy balance.

• A good method that can be used to get the heifers cycling 'earlier', actually does not really get them cycling earlier. What you do is breed the heifers 2-6 weeks earlier than the cows, so they will calve earlier that the cows. If they calve earlier, they will have longer that the cows to start cycling. If you have a restricted breeding seasons, the heifers will be cycling when the cows cycle.
• You can weigh the cows 100 days before calving. The weight 24 hours after calving should be the same as that 100 days before calving. This take into account the fetus and placenta being delivered at parturition. Obviously, this is more of a historical finding and is not a practical preventative measure.
• Body condition scoring at weaning
  • This is an ideal method to ensure adequate prepartum nutrition. You use a system of body score condition when the calves are weaned. (Calves are generally weaned at about 205 days postpartum, so the cows should be about 100 days pregnant.)
  • The scores are :1-3: emaciated, 4 borderline, 5-7 good fat 8-9 fat.

• The goal is to have a more positive energy balance postpartum, so if a cow is 8-9 it is too fat and does not need supplements. A score of 5-7 is good. If cows are <4, then extra supplementation will help them cycle earlier postpatum. You can also wean earlier so the calves do not pull the cows down so much, this will also result in a lower weaning weight.

Availability projection tables for mature cows-per cent conception-prepartum nutrition level (before calving)

Mature cows Conception Rate when fed Prepartum
Days rest	Low TDN	Mod TDN	High TDN
90	85	92	95
80	80	90	95
70	70	85	92
60	47	80	90
50	25	62	77
40	25	45	65
30	10	29	40
20	10	12	15

Availability projection tables for mature cows-per cent conception-postpartum nutrition level (before breeding)

Availability projection tables for first calf heifers -per cent cycling-prepartum nutrition level (last trimester before calving)

Availability projection tables for first-calf heifers-per cent cycling-postpartum nutrition level (after calving and before breeding)

From The Cowpedia, Syntex Agribusiness, Inc. (IBB), 1975

TDN = total digestible nutrients

• Suckling by the calf inhibits cyclic activity in the cow by decreasing LH release. 
  • If we look at the time to resume cycling in cows that had experimental postpartum mastectomy (no lactation), they had the shortest interval to first heat. 
  • If a cow is milked twice a day (like most dairies) she cycles back fairly soon. 
  • If 1 calf is sucking, it takes a little longer
  • Four times a day milking takes even longer 
  • 2 calves sucking make the longest interval to first estrus.
  • Physical suckling may not be all. Sight and smell by the dam may be important too
• This suckling effect can be alleviated by early weaning of the calf or 48 hour calf removal at start of breeding season (called Shang Treatment).

• Dairy cows are usually fed well and few problems with true anestrus. However, very high producers may be in negative energy balance for a longer period of time and may not cycle back as soon. This is because maximum feed intake does not coincide with the maximum milk production.
• The average dairy cows resumes cycles 21 days after calving.
• Some dairy heifers may be stressed or low on the 'peck order', which causes anestrus or subestrus.

Vitamins and minerals 420, 426

• Vitamins and minerals are often suspected in infertility and anestrus, especially by feed salesmen, but little hard evidence supports these claims.
• Urea has no effect on reproduction.
• Carotene is needed by the CL. If it is low the cow may have low progesterone and irregular cycles.
• Copper requirements are 10 ppm. Less than that may cause anestrus.
• A cobalt deficiency may cause a delayed first estrus and irregular heats.
• Mn requirements are 40 ppm. Less than this may cause anestrus or irregular heats.
• Phosphorus is hard to separate from energy. It is associated with the seed portion of plant. Cows fed at 66% NRC had no change in pregnancy rates. Cows fed at 50% NRC for 8 months, however had lower pregnancy rates. Experimentally low levels also delayed puberty in heifers.

• Cows need to attain a specific weight at a specific age to attain puberty. Puberty is more weight related than age related.
• Goals for breeding weights

• However, a report out of U.K. showed increased economic benefit over the life of the cow by breeding at a target age of 15 months, even if the heifers haven't reached the target breeding weight.

• Ovarian atrophy is caused from nutritional problems and is most often seen in high production dairy cows.

• Silent heat is generally not a problem and usually is manifested by unobserved heats by producer. However, the first postpartum heat is normally silent, because there are no estrogen receptors. This is a result of the low postpartum progesterone. Since the progesterone is needed to induce the estrogen receptors, the estrogen are receptors are absent and heat is silent.

• If a cow ovulates more than 18 hours after end of heat, then ovulation is said to be delayed. This may be diagnosed by palpation and can be treated with GnRH. This only occurs in < 2% of cows and is more likely to be a heat detection problem.

• A pyometra is a uterus filled with pus that has a closed cervix and a CL3 on the ovary. The pus prevents the normal luteolytic mechanism from happening. This results in anestrus.
• The fluid in the uterus mimics a pregnancy, so the cow will not return to heat.

• Treatment is prostaglandin to lyse the corpus luteum.

• A mummy in the uterus will simulate a pregnancy and prevent the normal luteolytic mechanism from happening. This results in anestrus. 
• Treatment is prostaglandin to lyse the corpus luteum.

• If only one uterine horn is present, because of a Müllerian duct formation problem, and a CL forms on the contralateral ovary, anestrus results. This persistent CL is because of a lack of the utero-ovarian countercurrent exchange from the uterine horn ipsilateral to the corpus luteum. This condition actually led to the discovery of the ipsilateral counter-current exchange mechanism.

349-351

• The definition of a follicular cyst is:
  •  A fluid filled structure on the ovary greater than 2.5 cm in diameter 
  • No CL3 present on either ovary. 
  • The cyst may persist for more than 10 days or regress and be replaced by another cyst.

• There are actually two types of cysts, follicular and luteal.
• A follicular cyst consists of a fluid filled cavity (unovulated follicle) lined by a small layer of thecal cells. The thecal cells produce progesterone, but do not have prostaglandin receptors. If there are no prostaglandin receptors, the normal luteolytic cascade cannot occur, resulting in anestus.
• If the granulosa cells persist in an untransformed state (not large luteal cells), the cow will show signs of constant estrus because of the estrogen production.
• A luteal cyst has a larger thecal (luteal layer) that may have enough large luteal cells to respond to exogenous prostaglandins.
• A cystic CL is just the cavity in a normal CL that is part of the normal progression of CL development.
• Recent work has shown that there is a turnover in follicular cysts and that they are not static structures

• Constant estrus may be seen if the granulosa cells produce estrogen. This is not the most common sign and is often 'diagnosed' by the producer.
• Anestrus is the most common sign. The thin luteal layer, with no prostaglandin receptors produces enough progesterone to prevent LH release and cause anestrus. This is the most common sign and is the important one for a veterinarian to diagnose the cause of anestrus.

• The cysts are caused by a lack of LH surge. The LH may actually be present, but may not be released. This results in no ovulation, minimal luteinization.
• It is an hereditary disease and elimination of bulls that have cystic daughters decreases he overall incidence in a breed.
• Administration of estrogen in proestrus can cause too early a release of LH, so when the cow really needs the LH for ovulation, it is not present. Aberrant estrogens in cottonseed meal, or possibly in poultry litter fed to cows may cause a large number of cysts in a dairy.
• Stress may also contribute to lack of LH release.

• A successful treatment is considered to be a return to a normal heat. 
• If cows with cysts are not treated:
  • 30% come into heat in 0-30 days
  • 39% come into heat in 30 -300 days
  • 30% take over 300 days to return to heat (basically not cured). 
  • Why do some cows return to heat? The small luteal cells can change into large luteal cells with prostaglandin receptors. Now the luteolytic cascade can take place.

Manual rupture

• Possible side effects of manual rupture include bleeding and adhesions.
• Manual rupture is no better than no treatment at all and should not be considered as a treatment at all.
• I will rupture a cyst diagnostically to differentiate it from a large, round CL.

• hCG is a glycoprotein and can result in antibody formation.
• Administration of hCG results in 80% of cows treated in heat within 19 days, and you can expect heat in 15-30 days.
• The dose is 10,000 IU, IM; or 5000 IU, IV. Cost and availability is becoming more of a factor. hCG comes from the urine of pregnant women and AIDS has put a scare into its harvest. It is still available, however.

• GnRH is a decapeptide and does not cause antibody formation.
• The dose of Cystorelin is 100 micrograms IM.
• You can expect the same treatment results as with hCG.
• Which cows should you treat. 
  • As many as 50% of all cows earlier than 50 days postpartum will have a spontaneous regression
  • Only 20% spontaneously regress if diagnosed after 50 days postpartum. 
  • However, it is most economically beneficial to treat all cysts whenever they are diagnosed.
• A follow up with prostaglandin in 10-14 days will hasten return to estrus.

• OvSynch method to treat cysts

• In refractory cases, progesterone can be administered to create an artificial luteal period. The progesterone inhibits LH release, and the abrupt progesterone withdrawal results in an LH surge. .