Anestrus is a transient pause of the reproductive cycle marked by the lack of estrus signals. Anestrus is a multifacet problem but its incidence indicates improper nutrition, stress from environment, uterine pathology and improper management. The incidence of anestrus is more in buffalo compared to cattle. High milk production is desired in dairy enterprise which is achieved when all animals have regular reproductive cycle and good fertility. Skip in one estrus cycle cause loss because inter-calving interval increases and there will be a longer dry period and shorter Lactation length. Anestrus causes an estimated loss of Rs. 193 per cow reported by Pawshe et al. (2011) and in buffalo it is Rs. 372.90 per buffalo reported by Kumar et al. (2013). This article highlights on major causes of anestrus and the management of anestrus condition.
Factors affecting anestrus
Nutrition :- Malnutrition or under nutrition is the most common cause of anestrus in heifers, in tropical countries poor quality feed and shortage of feed is the probable reason for malnutrition. In high yielding animals due to high metabolic load nutrients are utilized for production instead of reproduction. Vitamins like Vitamin A, Vitamin D, Vitamin E and minerals like calcium, phosphorus, copper, zinc and iron play significant role in action of enzymes and hormones, deficiency of minerals affect reproductive performance. Not only underfeeding cause anestrus but overfeeding also leads to anestrus, high feed intake causes high metabolism which promotes clearance of ovarian hormones from body.
Body condition score :- Body condition score reflects the nutritional status of animal and a major factor affecting reproductive performance. A desirable body condition score is 3.5(On scale of 5) at time of calving. Less feed consumption during late gestation and early parturition reflects low body condition score and it cause prolonged postpartum anestrus.
Environmental stress :- Extreme hot and cold affect follicular development and affect reproductive cycle in both cattle and buffalo. Reduced feed intake in summer results in low level of gonadotropin secretion. Heat stress also affect quality of oocyte, folliculogenesis and micro environment of follicular fluid.
Lactation :- Prevalence of anestrus is seen in high yielding cattle and buffalo. High level of oxytocin hormone provides negative feedback on GnRH-LH axis.
Suckling :- Ovarian activity get supresses by suckling after parturition resulting delay in postpartum estrus. Suckling induces secretion of prolactin, oxytocin and cortisol which provide negative feedback on GnRH-LH axis. These hormones supress GnRH secretion and ultimately reduce LH pulse frequency.
Parasitic infections :- Parasitic load is one of the common causes of anestrus among dairy animals. Parasitic infections like trypanosomiasis, fasciolosis and schistosomiasis cause weight loss and anemia which leads to anestrus. Parasitism also affects future productive and reproductive performance.
Genotype :- The restarting of postpartum cyclicity depends upon species and breed. The postpartum anestrus of buffalo is longer compared to cattle. The role of genotype is not completely known but it may be due to difference in physiology of different species and breeds, difference in feed intake and milk production.
Parity :- Longer postpartum anestrus is observed in primiparous buffaloes than pluriparous buffalo. As the parity increase length of postpartum anestrus decrease.
Periparturient Disease :- Abnormal calvings and disease like Metritis, Ketosis, Mastitis also influence onset of postpartum cyclicity. Inflammation affects secretion of GnRH and LH thus activity of ovary remains supressed in uterine infection.
Increased milking frequency:- Increasing the frequency of milking from twice to three or four times daily lengthens the interval from calving to first ovulation by less than a week. When milking frequency is increased from three to six times daily, the interval to first ovulation is lengthened, but still not to the same extent as that of frequent suckling. Therefore, increased milking frequency is only a minor contributor to anestrus.
Efficiency of estrus detection:- Unobserved estrus due to poor estrus detection efficiency can frequently contribute to anestrus, exacerbating the severity of the condition.
Negative energy balance:- Cows in negative energy balance are at a very high risk of anestrus and delayed onset of cyclicity. Elevated circulating concentrations of non esterified fatty acids are associated with adipose tissue mobilization and indicative of negative energy balance.
Housing type:- Cows under intensive housing systems compared with those on pasture have a higher risk of anestrus. Tie-stalled cows are more likely to be in anestrus than other types of housing because tie-stalled cows have few opportunities to form sexually active groups, limiting overt behavioural signs of estrus.
Management of anestrus
The best management of anestrus is to identify animal and management of predisposing factors. Various hormonal and nonhormonal compounds are used to restore cyclicity in animals. Plant based treatment has been used since long ago. Various parts of plants like root, bark, flower and leaves have active principles and some parts of plants are rich in minerals and vitamins which helps in restoration of cyclicity. Examples of such plants are curry leaves, kalonji, ashoka, methi, papaya and cucumber. These plant-based medicines are used singly or in combination to treat anestrus. Other method like utero-ovarian massage is cheapest, oldest and effective method to induce cyclicity. The probable mechanism of this method is increased blood circulation in ovary and uterus which increase availability of hormones. Uterine infections can be treated by flushing uterus by lugol’s iodine solution.
Painting of cervix by lugol’s iodine solution cause irritation and bring out reflex to secrete GnRH from anterior pituitary. Various hormone based medications used to treat anestrus. GnRH, prostaglandin, estrogen and progesterone are used alone or in various protocols to treat various ovarian dysfunction. To assure effective treatment, nutrient and health status of animal must be good, only deworming is not sufficient. Vitamin, mineral and antioxidant supplementation helps to achieve good health status in animals. Estrus detection and artificial insemination in animals should be done by trained workers as efficiency of estrus detection and insemination in animals also plays an important role in anoestrus condition. Further the animals should be prevented from negative energy balance and should provide with proper housing and space requirement to exert maximum reproductive efficiency.
Anmol Pareek1, Sandeep Kour2, Asma Khan3, Biswajit Brahma4, Dipanjali Konwar4
1 M.V.Sc Scholar, 2 Ph.D., 3 Professor and Head, 4Professor
Division of Livestock Production Management, F.V.Sc&AH, SKUAST- Jamm
