By -Dr Uday Kumar, (PETS & LIVESTOCK CONSULTANT)
Patna,
Oestrus is defined as a type of sexual behaviour near the time of ovulation which is characterized by the acceptance of the male. Anoestrus indicates the lack of this typical oestrus expressionat an expected time. It is a normal phenomenonin association with some physiological conditions (e.g. before puberty and during pregnancy), but becomes pathological when the duration exceeds the generally accepted average. In fact, post-partum anoestrus can be defined as the lack of oestrus symptoms (despite of effective oestrus detection) within 60 days after calving, while normal cows in exactly the same conditions already have been seen in heat. Perera, (2011) reported that longer postpartum anoestrus exhibited by bovines might be due to low secretion of luteinising hormones during this period. Physiologically post-partum anoestrus cannot be escaped because it is helpful in involution of uterus within 15–45 days after parturition most of the dairy cows recommence heat. One of the annoying problems in dairy industry is postpartum anoestrus.
Anoestrus is the major infertility problem in farm animals. It is important to note that anoestrus is a abroad term, which indicates the lack of oestrus expression at an expected time. The meaning depends on age, weight, breed and history. Delay in expression of oestrus is beyond accepted average in anoestrus. It must be understood that a period of sexual quietness in animals is shown by complete absence of oestrus cycles. Anoestrum as fertility problem may be true when animals have small inactive ovaries with no palpable GF and functioning CL on ovary with toneless uterus on three consecutive G/C examinations at ten days interval. Anoestrus condition is physiologically expected during pre pubertal stage, pregnancy, puerperal period and senile age but all other times animal should cycle regularly and manifest oestrus. The condition differs from suboestrus or silent oestrous. There are continuos oestrus cycles without any behavioral signs in suboestrus condition. Weak and silent heat continues unnoticed and the condition is presumed to be anoestrus. However palpable ovarian activity (GFI CL) is noticeable in subestrus. The incidence of anoestrus in bovines is considerably high and it is a worldwide problem. Delayed maturity, post partum anoestrus and post service anoestrus leads to economic losses. The problem of anoestrus is caused by various etiological factors that are interdependent and also complicated. The incidence and management of the anoestrus have been recognised as age old problems in cattle breeding and there is wealth of documentation on various therapies to induce estrus in cow and buffaloes.
Etiology:
(i) Nutrition: In India like tropical country, the dairy cows are habitually reliant on field grazing and by-products of seasonal crops for feed. This kind of the feed stuff have below 7.5% crude protein, so rumen efficiency is decreased and true digestibility of the feed also moderated. There is consequently a direct correlation between negative energy balance and a reduction in the release of gonadotropin releasing hormone (GnRH) . Thus indicating that nutritional deprivation decreases GnRH pulse frequency by enhancing hypothalamic inactivity. High lactation demand is positive correlated by means of intake of dry matter and energy that cause deviation in energy balance in postpartum cows.
(ii) Lactation: In high yielders prolactin hormones secreted more which cause negative effect on GnRH secretion. Finally it causes anoestrus due to insufficient FSH and LH hormones .
(iii) Suckling: During suckling teat it generate physical stimuli which cause release of endogenous opioids like endorphins. These opioids act as neurotransmitters through central nervous system and inhibit the release of luteinizing hormones. Resulting prolonged postpartum anoestrus. Suckling influences the length of the postpartum interval anoestrus in cows. Regulation of the suckling and lactation stimulus is a viable management option to decrease the post-partum interval and this can be achieved by complete, short-term (48 h) or partial (restricting suckling to short periods of time each day) weaning .
(iv) Season: Walsh et al. (2007) observed that if calving has taken place in winter season, dams are prone to maximum threat of anestrus. Season cause change in photoperiod stimulation in brain. Though dairy cattle’s are not seasonal breeders.
(v) Breed: Suckled dairy cows have longer postpartum interval than suckled beef cows.
(vi) Parity: Primiparous cows have longer intervals to first ovulation than multiparous ones and cows with lower energy balances have longer intervals than those with higher energy balances .
(vii) Stress factors: Especially thermal stress during gestation has an effect on subsequent lactation and reproductive efficiency resulting in anoestrus after parturition due to altered endocrine status
Types of Anoestrus ———–
There are four different clinical forms of anoestrus namely (i) Silent heat (ii) Cystic ovarian disease (iii) Ovarian a function (hypo-function) (iv) Corpus luteumpseudo graviditatis
1. Suboestrus: It is unobserved or silent heat. Cows suffering from suboestrus are not seen in heat at theexpected time after parturition although they are cycling regularly, as can be proven by progesterone profile analysis and rectal examination . Suboestrus is the main reason why cows are not seen in heat within 60 days after calving.
2. True anoestrus:
Cows in true anoestrus are characterized by low progesterone levels in milk and blood and inactive ovaries or ovaries with poor follicular growth . Prolonged periods of ovarian quiescence and anovulation are mainly due to lowered plasma LH levels. As a consequence, factors that suppress LH pulse frequency during the post-partum period will delay the first ovulation and lead to anoestrus. Although many stress factors are known to impair oestrus in the dairy cow by reducing the LH pulse frequency, it is generally accepted that malnutrition and an excessive Negative Energy Balance (NEB) are the main causes of delayed ovarian function after calving. Decrease in plasma LH levels caused by a lowered sensitivity of the pituitary to GnRH stimulation.
3. Pyometra
Pyometra is characterized by a progressive accumulation of pus in the uterus in the presence of functional ovarian luteal tissue, usually a corpus luteum or rarely a luteal cyst. During parturition the uterus is invaded by several kinds of bacteria like Gram-negative anaerobic bacteria (especially Fusobacterium necrophorum and Bacteroides melaninogenicus) and Actinomyces pyogenes. In cows with disturbed uterine defence and involution processes, as after a retainedplacenta, the self-clearance mechanism of the uterus can be perturbed. An exudative purulent response is generated in the endometrium and the ability of the uterus to produce or transport a sufficient amount of prostaglandins to cause luteal regression is compromised. As a result, the corpus luteum persists and since the genital tract remains under the continuous influence of progesterone without an intervening oestrus, the infective process progresses and a purulent exudate accumulates in the uterus. Cows which suffer from pyometra show little or no signs of ill-health. The main reason for them being examined is the absence of cyclic activity and sometimes the presence of an intermittent vaginal discharge. The diagnosis will be based on the anamnesis and on anextensive clinical examination.
4.Cystic ovarian disease ——–
Another common pathological condition leading to post-partum anoestrus in dairy cows concerns cystic follicular degeneration or cystic ovarian disease (COD). Cows are diagnosed as being affected by COD when they have one or more fluid-filled ovarian structures (cysts) of at least 2.5 cm in diameter that persist for at least 10 days in the absence of a corpus luteum, combined with cyclic irregularity characterized by anoestrus or nymphomania. Pathological ovarian cysts (follicular cysts and luteal cysts) arise as the result of anovulation of follicles. Cystic Ovarian Degeneration (COD) in dairy cattle occurs most frequently during the early post-partum period (30 to 60 days after calving), at the time of resumption of normal ovarian activity.
5. Pregnancy———-
It should be kept in mind that also pregnant cows do not cycle and will not be seen in heat. Especially in herds with a poor management and in those in which a bull has entrance to the cows, attention has to be paid to pregnant cows.
DIAGNOSIS————
Diagnosis will be based on the anamnesis, a general clinical examination, and an accurate gynaecological examination based on rectal palpation of the ovaries and the tubular genitalia, eventually aided by a vaginoscopical examination. Although rectal palpation is a valuable and cheap technique, more accurate techniques such as ultrasound imaging or progesterone analysis in milk or blood are required.
Treatment consideration ————
Treatment of anoestrous depends on cause, diagnostic facility, availability of drugs, acceptability! response to the drug by the animal, dose of the drug, duration of the drug response and health status of the animal. Cost of the treatment and easy availability of drugs in the market are also important in case of rural poors. Vague generalizations and empirical treatments are futile on many occasions. Treatment for anoestrus should not be undertaken unless body score condition and nutritive standard is optimum in animals. Treatment of anoestrous is practiced in both therapeutic as well as preventive manner. Although vast majority cases are presented to the clinic for therapeutic course, preventive approach is expected under modem and economic dairy management. Alleviation of all stress factors of the animal by improved managemental practices with corrections in housing, feeding, watering, grooming, exercise is highly essential at doorstep of farmer! breeder. This is possible only through mass education, veterinary extension and practical demonstrations by the veterinarian. The first approach in the line of anoestrous treatment should be emphasized on correcting nutritive management. The optimum and balanced diet should be worked out in anoestrus cases according to the blood biochemical analysis. Unless the blood biochemical levels are optimised, no treatment should be undertaken. The animal should first get maintenance ration for a period of fifteen days and then steaming up can be practiced with additional ration. Many animals resume ovarian cyclicity due to correction of nutritive requirements as a flushing effect. Levels of Co, Cu, Fe and Mn have shown to be lower than normal in both anoestrus and anaemic animals and hence supplementation of macro and micro mineral nutrition is beneficial. Use of iodine, calcium, phosphorus, copper, cobalt and vitamins are commonly practiced in oral or injectable form. Health of the animal is another important aspect in case of anoestrus. Chronic debilitating diseases should be treated first. In particular, parasiticide spray for ecto parasites and deworming therapy should be carried out. Skin infections, wounds, allopacia should be corrected by appropriate treatments. Skin luster should return to normalcy and it should be shiny. Similarly all the clinical diagnostic indices should become normal.
Stimulatory approach ———-
Ovarian massage is known to stimulate the cyclicity in some anoestrous cases. It is proved that the cervical stimulation with lugol’s iodine at very low concentration as paint or intrauterine infusion gives better response in inducing oestrus. Chemical preparations ex. clornephene citrate which has LH like effect in induction of ovulatory oestrus. Considering non hormonal property of the drug, clomephene citrate is preferred by practicing veterinarians
Herbal treatments————
Animals with gaining body weights always show tendency of resuming cyclicity. Quite often it is observed that the animals with optimum health, nutrition and management also show anoestrus. These animals require stimulus and ignition like effect to start ovarian cyclicity. The required stimulus can be very well charged with herbal preparations. Herbal therapies are cheap and they have no side effects. Similarly herbal treatments are convenient to administer (orally) and their nonhormonal properties render field vets to use them regularly. There are many herbal drugs for induction of oestrus. Herbal drugs contain various ingredients in various concentrations, all are used with a common principle of their oestrogenic property.
Hormonal therapies ———
Application of hormonal treatments in anoestrous cases should be used judiciously and only under the guidance of a trained veterinarian. Generally hormones are used for speedy results. Induction of oestrous (behavioural overt signs) should be aimed to have ovulatory response and subsequent conception. Hormonal treatments may prove unsatisfactory and produce unexpected results if correction of managemental and nutritional errors is aimed with hormonal treatment. Circulating levels of endogenous hormones cannot be estimated easily and repeatedly on hospital Ifarm levels and hence the use of exogenous hormones leads to “shooting in the dark” and the results are always valueless.
GnRH ————–
Only GnRH treatments in noncyclic cattle are not much encouraging. GnRH treatment might increase the probability of maternal recognition thus reducing embryonic loss and improving pregnancy rate of preceding AI through prolonging life of CL. GnRH treatments after a week or two after parturition gives negative effect in animals with uterine infections but positive effects with healthy uterine involution process. The application of GnRH two weeks after calving would enhance the chances of early resumption of cyclicity in post partum dairy lows.
Gonadotrophins————–
Use of gonadotrophins is of much less value in the treatment of true anoestrum. It is well established that FSH level is always optimum even in anoestrus stage. LH levels are low and episodic release is not continued in anoestrus. Since FSH and LH are protein hormones, their repeated use may possibly form antibodies. Non pituitary gonadotrophins are preferred for the treatment of anoestrus. PMSG (FSH) and HCG (LH) are used either seperately or in combination. However, exogenous LH is more commonly preferred due to low values of endogenous source or low sensitivity at ovarian level. PMSG may lead to multiple follicular developments.
Progesterone————–
Progesterone is widely used in the treatment of anoestrus with prime consideration of its safety. The withdrawal effect of the progestrone is essential for priming of hypothalamic – pituitary axis for initiation of next oestrous cycle. In true anoustrous cases, Induced hormonal dioestrus by progestrone is suddenly ended (like luteolysis) at removal of implant/injection of progesterone and a proestrous sequence occurs spontaneously resulting in oestrus and ovulation. In case only progesterone priming is not sufficient to induce oestrus and ovulation, gonadotrophins with long halflife (Non pituitary gonadotrophins, eCGIHCG) are essentially required.
Oestrogens————–
No pretreatment of progesterone prior to oestradiol will lead to oestrous without ovulation as there is no LH surge. Oestradiol administered after progesterone withdrawal can stimulate the onset of an ovulatory ‘cascade’ of LH. Oestradiol could produce oestrus and ovulation if administered during a spontaneous proestrus following a hormonal dioestus produced by progesterone. The recognised positive feed back effects of ODB to stimulate pulsatile release of gonadotrophins can be utilized to treat successfully anovulatory anoestrus. These feed back effects occur after priming the hypothalamic pituitary system with progesterone.
Multiple hormones ————-
Silastic implant impregnated with Norgestomet ie. synthetic progestogen is marketed as Crester. Norgestomet is a very potent synthetic progestin with a potency factor of 100 to 200 times that of the endogenous progesterone. Crester treatment requires no heat detection and fixed time AI can be carried out. Crester is a synchronisation method in cyclic animal based on short term progestrone treatment in combination with an anti luteotropic factor .The implant mimics CL without physically interfering with reproductive tract. The injection endures that natural CL has regressed at the time of implant removal. In true anoestrus, the Norgestoment will prime the reproductive system and will also inhibit secretion of pituitary gonodotrophins. With formation of artificial CL by norgestomet implant, it is possible to regress available ovarian CL by oestradiol valerate and immidiate imposing of block on pituitary by norgestomet through crester injection. PMSG given at the time of implant removal will stimulate follicular growth to induce fertile oestrus.
PRIO & CIOR ————
are intravaginal devices releasing natural progestenone over a period of time. Mode of action is similar to Crestar but the luteolytic effect/ component is provided as an Oe tradiol benzoate capsule attached to PRIO or injection of either Oestradiol or PG in CIOR. With PRIO & CIOR treatments heat detection is always necessary for appropriate time of AI. Never forget that no remedy can create fertility in animals. It is possible to boost and exercise control fertility in productive dairy animal.
