It simply means the animal is not coming to heat. If an animal is not coming to heat, it may become an economic burden on the farmers and thus the various reasons for anestrus should be diagnosed and treated accordingly to benefit the farmers. In general, the incidence of anestrus in cattle can be as high as 67% and 80% in indigenous cattle and buffaloes, respectively. Anestrus causes economic losses to the farmers due to increased calving interval, treatment costs, poor net calf crop, production loss, and mature animal replacement cost. The reasons for anestrus in cattle and buffalo may be associated with the body weight, nutritional status, heat stress, deworming and disease status of the animal. Anestrus during pregnancy is a normal physiological phenomenon and should not be confused as a reproductive problem. Postpartum anestrus is also a normal physiological phenomenon until and unless it gets extended over a period of 60-80 days. Ovarian atrophy, ovarian hypoplasia, persistent corpus luteum, or cysts and infection in the uterus may also lead to anestrus in animals.

It is the condition when the cows after calving do not come to estrus and show no sign of heat for several weeks. This is a period of temporary infertility in the cattle and buffaloes which cannot be avoided. However, the period should be managed so that the period does not get extended and the animal returns to its fertile stage in a timely and economically efficient manner. The animal should conceive within 80-85 days after calving, for the economic benefit of the farm and farmers. But the animal should normally come to heat after 60 days of parturition. The causes of postpartum anestrus in cattle and buffaloes are often multifactorial and are broadly classified into: physiological (suckling, parity, milk yield, breed etc), nutritional, managerial (feeding management, milking frequency, length of dry period, estrus detection efficiency etc.), environmental (design of animal shed, stall, season, weather, etc.) and pathological (cystic ovaries, uterine inflammation, dystocia, mastitis, lameness, etc.).

It is the condition when the animal does not show observable behavioural signs or symptoms of heat, though the animal is in heat and the reproductive organs show cyclical changes. Silent heat is one of the major problems in dairy animals and is observed in around 10-40% of animals in the herd. Silent heat occurs when an animal does not produce enough progesterone. The causes of silent heat may be poor management in the herd, heat stress, under nutritional status of animals (deficiency of energy, mineral and vitamins), hormonal imbalance, and high concentration of isoflavones in ration. Silent heat is more prevalent in buffaloes than cattle because of the inefficient thermoregulation system in the buffaloes under high environmental temperatures and high humidity. Silent heat is also more prevalent in the high yielding cattle population.

A repeat breeder animal has normal estrous cycle, has no abnormal vaginal discharge, has calved at least once and is less than 10 years old, but has failed to conceive after at least three or more consecutive inseminations. In simpler terms, apparently a normal animal does not get pregnant even after repeated insemination or mating and comes to heat regularly. The incidence of repeat breeding in cattle and buffaloes has been reported to be around 20 to 30%. Repeat breeding causes economic loss to the farmers by increasing intercalving interval, increased cost on treatment and insemination, production loss, and increased cost of mature animal replacement. The major causes of repeat breeding in the animals are nutritional deficiency, genetics, anatomical abnormality, age, infection, endocrine imbalances, improper insemination etc. But still there are cases where no cause of repeat breeding may be identified.

Normally, a cattle or buffalo expels placenta or fetal membranes within 2-4 hours after the parturition. In some cases, it may get delayed by 8 to 12 hours also. After parturition, if the cow does not expel placenta within 24 hours the case is termed as retention of placenta (ROP). ROP is more common in animals having history of abortion, dystocia, stillbirth, twin birth, hypocalcemia, high thermal stress due to environmental temperature, premature parturition, placentitis and imbalanced diet during pregnancy. If placenta is not removed, the animal may suffer from inflammation, fever, prolonged calving interval, decreased milk yield, uterine infection, metritis and the animal may die in some cases. The animals with ROP are also at higher risk of displaced abomasum, mastitis, ketosis and early lactation culling. ROP causes economic losses to the farmers by decreasing milk yield, prolonged calving interval and expenses on the treatment of animals.

If the animals are not managed scientifically, fertility status of animals or animal herds may get affected. In general, breeding health of the stock in the herd is estimated by the conception rate of the animals in the herd. Conception rate of the herd should be estimated as the percentage of animals getting pregnant after first service. Conception rate of individual animals or of herds can be easily checked from breeding records. But to test the conception rate, it should be ensured that the semen used in the herd for insemination of animals is from bulls having high fertility rate. Breeding health of animals and herds is also affected by other management conditions. Some of the conditions include animal shed is not prepared scientifically, animals are not given balanced ration and fodder, estrus detection is not done properly, AI is not done at the right time by trained people, naturally bred with diseased animals, etc.

Diseases caused by bacteria, viruses or a parasite may also cause reproductive failure in the farm animals resulting in sub-optimal reproductive efficiency and thus production. Symptoms of most of the reproductive diseases are similar i.e. mostly the animal does not conceive, may return to heat repeatedly, or may miss few cycles of heat or does not come to heat at all, reduced pregnancy rate in the herd, increased incidence of the abortion, white or creamy discharge from vulva etc.. But disease diagnosis is the most tricky part in order to know the exact cause of low fertility and requires the services of trained veterinarians and also/ often a veterinary laboratory. Farmers may not even realize that there is a problem until an unusually large number of cows are diagnosed non-pregnant. Common diseases causing infertility in the cattle and buffaloes are leptospirosis, brucellosis, metritis, pyometra, listeriosis, vibriosis, campylobacteriosis, infectious bovine rhinotracheitis, bovine viral diarrhoea, trichomonas, to name a few.