Infertility: A Challenge Exploring Successful Solution

Role of Reproductive Technologies

Good reproductive performance is essential for efficient livestock production, so improvement programs should increase reproductive efficiency to the extent that this can be justified economically. The females must grow rapidly to attain sexual maturity, initiate estrous cycles, ovulate and be mated by fertile males or inseminated with viable semen at the proper time for any chance of conception. At a micro level, each missed heat is a missed opportunity. For each heat missed the farmer incurs a loss of milk production of 21 days, in addition to bearing the feeding cost for animal maintenance. This tantamounts to about Rs.5500. Artificial insemination (AI), which is a normal practice in cattle, is not as successful in buffalo especially in hot summer months, because of the weakness of oestrus symptoms and the variability of oestrus length, which make oestrus detection very difficult. Scientists the world over are working on developing new estrus synchronization protocols which can reduce the ovulation time window post synchronization so as to practice insemination at a fixed time thereby obviating the need for heat detection which is a serious problem especially in buffaloes. The application of two protocols-ovsynch and heatsynch-for estrous synchronization and fixed time AI were successfully attempted in buffaloes (Fig.1 and 2) both in the farm as well as in farmers herds with a success rate for conceptions ranging from 40-50% also in animals suffering from anestrus or repeat breeding.

New Studies on Pregnancy Rates

Research studies on dairy cows have demonstrated that the success rate of the Ovsynch and Heatsynch protocol is dependent on the estrous cycle stage at the onset of the protocol. For example, the initiation of the Ovsynch protocol between days 13 and 17 or early in the estrous cycle (days 2–4) led to a reduced pregnancy rate. Other studies have established that GnRH induced follicular turnover or induction of a new follicular wave is the most efficient if ovulation is induced in response to the first GnRH treatment and that resetting the follicular development can produce a new dominant follicle containing an oocyte with greater potential fertility. Hence, a new estrous synchronization method that includes the administration of an additional PGF2 injection 48 h before beginning the Ovsynch protocol was developed which was named the Doublesynch (the abbreviation of double 

synchronization) protocol, as it resulted in synchronized ovulation after both the first and second GnRH treatments. In a limited study conducted on buffaloes the pregnancy rates were 60% using TAI doublesynch application on cycling buffaloes, and, 55% for anestrus buffaloes, in comparison to 27.3% for cycling buffaloes inseminated following spontaneous estrus. The overall pregnancy success rates after the Doublesynch protocol in both cycling and anestrus buffaloes increased by 30.8% compared to spontaneous estrus (58.1% vs. 27.3%). The study demonstrated that the Doublesynch protocol followed by TAI significantly enhanced the pregnancy rate in cycling and anestrus buffaloes in comparison to untreated controls even during the low breeding season (summer). By substituting the second GnRH injection of the Doublesynch protocol with estradiol benzoate another novel estrous synchronization protocol – estradoublesynch- has recently been developed (Fig.3). Estradiol benzoate has some advantages compared with GnRH (i.e., cheaper hormone price, easier scheduling and implementation for injection and insemination, greater uterine tone, ease of insemination, and occurrence of estrus as has been recorded using the Heatsynch protocol. The success rates in terms of percentage of buffaloes conceived were very similar to that obtained using the doublesynch protocol in buffaloes. The techniques of doublesynch and estradoublesynch hold promise and need to be validated in farmers' herds.

B.S. Prakash, Assistant Director General (AN&P), Animal Science Division, ICAR, Krishi Bhawan, New Delhi-110001