Dr. Kaushlendra Narayan Dwivedi
Carus Laboratories Private Limited
|Anestrous is a temporary loss of reproductive cyclic event in animals. It is a multifactorial problem and occurs due to inadequate nutrition, environmental stress, uterine pathology, and improper managemental practices in farms. It can be classified on the basis of physiological and pathological conditions of the animals. Diagnosis is based on the history &different causative factors. Many chemicals (hormonal and nonhormonal) are being used as therapeutic agents for the cure of anestrus. Factors influencing the resumption of regular cyclic activity after calving like nutrition, reduction in body condition score, suckling calf, lactation length, dystocia, species, breed, age, parity, the month of calving, uterine pathology& debilitating disease. Keywords: Anestrous, Stress, Nutrition, Dystocia, Prevention, Treatment|
Anestrus is one of the most common reproductive problems in cattle and buffalo in the Indian subcontinent. This problem is more severe in the dairy sector which affects livestock productivity and economics to a great extent. It is a functional disorder of the reproductive cycle which is characterized by the absence of signs of estrus either due to lack of expression of estrus or failure of its detection. Anestrus is commonly observed in post-pubertal heifers, lactation, and in the early postpartum period in adult animals. Anestrous is reversible in high-yielding animals, but its reoccurrence depends upon inadequatenutrition, particular species, breed, parity, season, environmental stress, and improper managemental practices. Diagnosis of this condition is based on the exploration of the different causative factors. Anestrus leads to economic losses through increased inter-calving interval, poor net calf yield, production loss and treatment expenses.
- FACTORS AFFECTING ANESTRUS
Feed given to the animal fulfills the requirement of maintenance, growth, production & reproduction of the animal. The nutritional status of animals affects follicular growth, maturation and ovulation (Diskin et al., 2003). Undernutrition is one of the most prevalent causes of anestrus in heifers. Long postpartum period of anestrus (>5 months) is normally found in cattle in the tropical area under free-range rearing system, probably due to shortage of feed and fodder. Less amount of feed intake during late gestation or early postpartum period leads to negative energy balance (NEB). Under high metabolic load, nutrients are utilized for production rather than reproduction (Ferguson, 2001) enhances the postpartum anestrus period. Along with negative energy balance, the deficiency of minerals like calcium (Ca), phosphorus (P), copper (Cu), zinc (Zn) and manganese (Mn) are also associated with anestrus (Hidiroglou, 1979; Campbell et al., 1999). Minerals works as Co-factor (catalyst) in enzymatic reactions thusit is well established that minerals play an intermediate role in the action of hormones and enzymes at the cellular level and its deficiency ultimately affects the reproductive performance of females (Bearden et al., 2004).
These problems can be controlled by supplementation of chelated minerals according to the animal’s demand.
1.2 Body Condition Score (BCS)
A visual and tactile evaluation of body fat reserves in bovines using a 5-point scale with 0.25 point increments. Body condition scores (BCS) are an indirect estimate of energy balance. Body condition score is the measure of the nutritional status of animals and is an important factor influencing reproductive performance (Baruselli et al., 2001). Extremes of BCS (very low and very high) at pre–calving, calving and early postpartum period delay the onset of cyclicity. However, for optimum reproductive performance, a BCS of 3.5 (on a five-point scale) is required at calving. Restricted feed intake during late gestation and early postpartum period results in low BCS, consequently, leading to prolonged postpartum anestrus (Dziuk and Bellows, 1983; Robinson, 1990).
1.3 Environmental Stress
Enzymes in the body act as biocatalyst for different metabolic reactions. All the enzymes in the body work efficiently at optimum temperature. Extreme cold and hot environmental conditions affect the growth & maturation of follicles in both cattle and buffaloes. Although Indian cattle are well adapted to hot and humid climates, however, ovarian activity is greatly reduced by heat stress and manifested in the form of anestrus. New follicle formation, follicular fluid microenvironment and oocyte quality are affected by heat stress. In buffaloes, a decline in feed intake during summer results in reduced secretion of gonadotrophins (El–Sawaf et al., 1979). Besides this, high environmental temperature suppresses the secretion of gonadotrophin which leads to alteration in ovarian folliculogenesis and steroidogenesis. Supplementation of biotin, chromium (Cr)& Vit.E is very helpful to reduce environmental stress by enhancing the glucose uptake to cells and neutralizing the free radicals.
Longer postpartum anestrus or weaker signs of estrus have been observed in high-yielding cattle & buffalo. El–Fadaly (1980) reported that buffalo producing >8 liters of milk per day had longer postpartum anestrus (107±36 days) than those producing <8 liters per day (77±30 days).
Suckling stimulates the secretion of some hormones like prolactin, cortisol and oxytocin that have a negative effect on GnRH–LH axis. Suckling suppresses postpartum ovarian activity both in cattle and buffalo so that it extends the postpartum anestrous period. Moreover, postpartum anestrous is longer in continuously suckled than in restricted or partially suckled cows and buffaloes (Bastidas et al., 1984; Nordin and Jainudeen, 1991). Nowadays early weaning of calves are practiced to minimize the postpartum anestrous period.
Parasitic infestation decreases feed intake and production, which makes the stressful animal & leads to infertility. Heavy parasitism is very common in growing calves. It affects the future productivity and reproductive efficiency of animals. Parasitic infection like fascioliasis, theleriosis, schistosomiasis, and trypanosomiasis infection in animals cause anemia and weight loss and ultimately results into anestrous. Recently, it has been found that Neosporacranium infection (Neosporosis) is widely prevalent among dairy herds and has a significant association with anestrus (Bruhn et al., 2013).
The genetic constitution of an animal is a very important factor to determine the productive & reproductive performance of the animal. The resumption of postpartum cyclicity depends upon species as well as breeds. The period of postpartum anestrus is usually longer in buffalo than the cattle. Genotype affects the physiological differences among breeds and species, differences in milk production and feed intake (Short et al., 1990).
Periparturient Diseases such as abnormal calving, assisted calving(dystocia), metritis, mastitis and ketosis also affect the postpartum cyclicity (Fonseca et al., 1983; Opsomer et al., 2000). Delayed uterine involution also hold up the resumption of ovarian activity. Postpartum uterine infection (clinical or sub clinical) suppresses GnRH release and LH secretion and due to inflammatory response (Sheldon and Dobson, 2004; Herath et al., 2006; Williams et al., 2007) ovarian activity remains suppressed in uterine infection.
1.8Congenital Anestrous / Free martin:
A freemartin is a female born twin to the male calf,90% are sterile. Partial expression of TDF (testicular determining factor) from male Y chromosome inhibits the female gonad also
MIF (Mullarian inhibition factor) from the male prevents Mullerian duct formation, so no uterus forms thus heifer becomes sterile.
- DIAGNOSIS OF ANESTRUS
Failure or absence of signs of estrus by the heifer or 60–90 days post-partum in the case of the adult; symptoms of estrus shown with cyclicity which subsequently ceased and revert into anestrus. Such cases are diagnosed when presented for pregnancy diagnosis. When livestock farmers complain that they are not able to detect estrus or have not seen any signs of estrus in that particular animal for long, means the animal in anestrus.
2.2 Progesterone Estimation
True anestrus is usually characterized by a lack of ovarian progesterone production (Peter et al., 2009). The presence of basal level (0.5–1 ng/ml) of progesterone in the blood samples at an interval of 8–10 days further confirms the diagnosis. If the concentration of progesterone is more than 1ng/ml, it is suspected of the presence of persistent corpus luteum.
2.3 Vaginal mucus Histopathology
Mucus swab taken from the vagina of the suspected animal and examination under the microscope after the staining gives information about the ovarian cyclicity.
2.4Per rectal Examination
It is a very common method of pregnancy diagnosis in rural India. Pregnancy can be a prominent cause of anestrus and therefore must be observed out by careful examination of the ovary and uterine horn when any animals present for gynecological examinations. On perrectal examination, ovaries are smooth, small and inactive with the absence of corpus luteum, Functional corpus luteum can be palpated in case of silent estrus as well as in anestrus. In case of any type of cyst found in one or both ovaries, the animal is much away from conception & pregnancy. In the case of a follicular cyst animal is always in heat or desires to mate eagerly at regular time intervals but does not conceive and if the animal never comes in heat means a luteal cyst may be found. Both cysts can be diagnosed by per rectal palpation or USG.
Ovarian pathology which is not accurately determined by per rectal palpation can be visualized by ultrasonography. It gives accurate information about different stages of follicular growth and the type of anestrus can easily be detected by ultrasonography. It can also differentiate between persistent follicles and persistent CL. Persistent follicles can be released by synthetic GnRH Buserelin acetate (Ashored) and persistent CL can be removed by ovulation with synthetic PGF2α cloprostenol (Zolcol) thereby restoring the estrous cyclicity.
Prevention of anestrous is preferable over treatment and can be achieved by maintaining the healthy status of the animals by adopting efficient farm management practices. Nutrition is probably more important factor, affecting ovarian activity. Special attention must be given to prevent the negative energy balance in high yielders. It can be achieved by providing adequate ration during the pre-and postpartum period. The supplementation of ‘Bovimin-B Ultra’ mineral mixture powder having vitamins, minerals and antioxidants in feeds are very helpful in the restoration of cyclicity of estrous.
Anestrus can be treated according to their cause, however; there is no single panacea to correct it. Various therapeutic agents including hormonal and non–hormonal compounds have been used extensively for the restoration of cyclicity in anestrus cattle and buffalo by several workers with varying degrees of success. In order to ensure effective treatment, the health and nutritional status of the animals must be in good condition. Besides deworming, the supplementation of vitamins, minerals and antioxidants in the feed is useful to improve the health status of the animals. Utero-ovarian massage is the oldest, simplest, cheapest and most effective method to
induce estrus in anestrous cattle and buffalo. Proper treatment with intrauterine suspension (Utriplex) against the uterine infection.
In the current scenario anestrous is the most commonly occurring problem in India. When we set new target day by day to achieve higher and higher milk production, due to huge pressure on animals for production, thus animal comes under stress and becomes more susceptible to the occurrence of anestrous. Milk production reached more than two times in India in the last two decades. ie: milk production was 84.4 million tons in 2001-2002 which has drastically increased to 221.1 million tonsin 2021-2022 and per capita milk availability shifted to 444 grams/Day from 222 grams/Day in the last 20 years. Anestrus is the result of mismanagement in rearing, feeding, reduction in body condition score, suckling calf, lactation, dystocia, species, breed, parity, uterine pathology &other debilitating diseases. once the reasons are taken care the animal normally comes in estrous except for congenital anomaly.