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Anestrus

It is defined as absence of periodic manifestation of estrus, with the absence of palpable follicular or luteal structures (smooth ovaries) or absence of normal physiological signs of estrus associated with  a corpus  luteum (subestrus, physiological anestrus). Inactive or non-functional ovary is one of the most important causes of anestrus in buffaloes. Anestrus is one of the most commonly occurring reproductive disorders in buffaloes. Ovarian inactivity is more frequent (30%) in buffaloes on low level of feeding than in those given high level feeding and also in summer (41–46%) than in other seasons (7–33%) calvers. Ovarian inactivity constituted 28% of all the functional causes of infertility in postpartum buffaloes and 67% of all cases of inactive ovaries in these buffaloes. Incidence of anestrus is buffalo 20-67%.

Summer anestrus is the major problem occurring in buffaloes caused by many factors. Ameliorating or eliminating those factors has proved useful in reducing anestrus in buffaloes with varied degree of success. They are through management, nutritional, breeding and hormonal approaches.

Management strategy

  1. Reducing heat stress : Proper extensive housing system and sprinkling of water to the body surface or providing wallowing facilities during hotter part of the day in summer can reduce the heat stress considerably, reducing the adverse effects on buffalo fertility. Various show that conception rate was increased in buffaloes by giving showers in addition to wallowing facilities, which considerably reduced the incidence of early embryonic mortality.
  2. Improving estrus detection methods:  One of the factors that increase the calving-conception interval of buffalo during the hot season of the year is poor detection of estrus. The use of teaser bulls, tail head paint, the heat watch system, radio-telemetric pressure transducers and pedometers can improve estrus detection and thus fertility.

Feeding strategy

Feeding strategy for buffaloes during hot climate is imperative in reducing infertility problems. Roughage feeding during night to buffaloes will reduce the heat stress in buffaloes. Moreover feeding green fodders, ad- libitum water and mineral mixture supplementation improve the efficiency of reproduction during summer. There are several key areas of nutritional management which should be considered during hot weather. These include formulation to account for reduced dry matter intake, greater nutrient requirements during hot weather, dietary heat increment, and avoiding nutrient excesses. It is important to predict dry matter intake, in order to formulate an adequate diet for buffaloes in a hot environment. The energy requirements of lactating buffaloes also increased under high temperature conditions, but this increase seemed to be caused mainly by the increase in metabolic energy. Low fiber, high fermentable carbohydrate diets lower dietary heat increment compared with higher fiber diets. Although the metabolic energy of dairy buffaloes increases in a hot environment, heat stress depresses feed intake.  

Breeding Strategy

There are many aspects of genetics that influence the response to heat stress, and as the variation among breeds is large. The maintenance of body temperature is heritable through characteristics including sweating competence, low tissue resistance, coat structure and color. So selections of animals through specific markers for heat tolerance will address the problem of heat stress in buffaloes.

Hormonal treatment

Various hormonal treatment regimens are followed to alleviate anestrus to stimulate ovarian activity, estrus behavior in turn leading to ovulation. Different hormones were used either alone or in dierent combinations producing varied degrees of success.

Progesterone based treatment regimens (PRID, CIDR, Crestar, Progesterone injections) either alone or in combination with gonadotrophins proved to be very effective in inducing ovarian activity in summer anoestrus buffaloes. The mechanism derived out of the treatments seemed to be the induction of follicle turnover by increased serum progesterone after PRID removal. It is further confirmed that the increased progesterone level in blood sensitizes the hypothalamus and pituitary to the gonadal feedback. Furthermore, PRID in association with PMSG yielded better results than PRID alone, both in terms of oestrus induction and conception/pregnancy rate. Moreover, ovsynch protocol alone or with other hormones is also useful in estrus induction and improved conception rate in buffaloes. Induction of follicular wave is also done using ECG in ovsynch protocol.  A double insemination is thus recommended to approach the time of ovulation for achieving better conception rates. Use of estrogen is also followed in treating anestrus in buffaloes. Approaches using other drugs such as melatonin, bromocriptine and antioxidants have been used with varied success rates.

Progesterone based treatment either alone or in combination with PMSG resulted in estrus induction (2.7-100%) and the conception rate varied from 50-100%. The success rate of PGF2α based treatment regimens in estrus induction varied from 58.3-89.5% with a conception rate of 13.8-75%. GnRH based treatment alone or in combination with insulin, progesterone, PMSG success rates in estrus induction and conception rate varied between 10.4-100 and 0-75%. Induction of estrus using ovsynch plus protocol with PMSG yielded estrus induction and conception rate of 80 and 30%, respectively. Induction of estrus Using miscellaneous drugs showed varied results: melatonin (55.5-100%), bromocriptine (56.2%) and antioxidants (22.2%).

Contributed by Indrajeet Singh ,Jerome A and A.K Balhara