Synchronization In Ewes Research Articles

Comparison of a controlled internal drug release device containing progesterone with intravaginal medroxyprogesterone sponges for estrus synchronization in ewes

Intravaginal progestagens have been used for many years to synchronize estrus in ewes. This experiment compares two such treatments: 60 mg medroxyprogesterone (MAP) sponges and a controlled internal drug release (CIDR) device containing 366 mg natural progesterone. No pregnant mare serum gonadotropin (PMSG) was used. Treatments were given to groups of 10 to 20 ewes for 14 d at various times during breeding season. Rams were introduced 1 d after treatment removal, and day of mating was recorded. Rams were removed after 3 d. Pregnancy was checked with ultrasound 60 d later. There was no diffeence in rate of marking by rams (88%) or pregnancy rate (57%) between treatments. Ewes receiving CIDR devices showed estrus earlier and with closer synchrony (P < 0.01). The CIDR device is comparable to the MAP sponge for estrus synchrony during the breeding season, and reasonable fertility can be achieved without the use of PMSG.

Fertilization and embryonic survival in ewes synchronized with exogenous hormones during the anestrous and estrous seasons.

Causes of reproductive loss in ewes synchronized and mated during the anestrous season and during the normal breeding season were compared with those for natural cyclic ewes mated in season. Synchronization of ewes in season and out of season with progestogen: pregnant mare serum gonadotropin (PMSG) increased ovulation rate, but the percentage of ewes ovulating did not differ from that noted for untreated ewes mated in season. However, synchronized ewes exhibited markedly higher total reproductive losses, both in season (49%) and out of season (58%), than did untreated ewes mated in season (25%). The two primary sources of the increased reproductive loss in synchronized ewes were increased fertilization failure and increased embryonic mortality, regardless of season. The increased fertilization failure was accompanied by a decrease in the number of accessory sperm per ovum and decreased tubal sperm numbers. The increased embryonic mortality among treated ewes was associated with increased variation in stage of embryo development within ewe and advanced stage of embryo development, which indicated that asynchronies of timing of onset of estrus, ovulation and fertilization may have occurred in synchronized ewes. The high reproductive losses for ewes treated out of season was characterized by a marked increase in fertilization failure, compared with that observed for ewes treated in season, in addition to the relatively high embryonic mortality associated with the synchronization treatment. Semen quality of rams was lower out of season than in season. It was concluded that the reduced and more variable lambing response often obtained for ewes treated with progestogen: PMSG during anestrus may be due to decreased semen quality of rams and increased asynchrony of events in the ewe reproductive tract.

Synchronization of ewes during anestrus: influence of time of year and interval to onset of estrus on conception rate.

The effects of progestogen-gonadotropin treatment on estrous response, ovulation rate and lambing response of crossbred ewes were examined at two times during the anestrous season (May-June and July-August). Each ewe group was treated with progestogen pessaries for 16 days and injected with 750 IU pregnant mare serum gonadotropin (PMSG) on days 17 and 32 to induce two consecutive estrous periods. Data accumulated from single-sire matings of 500 ewes indicated that estrous, ovulation and lambing responses did not differ (P less than .10) between ewes treated in May-June (92%, 2.5, 66%) and ewes treated in July-August (93%, 2.5, 67%). We concluded that there were no significant differences between reproductive responses of ewes synchronized during mid-anestrus (May-June) and those of ewes treated during late anestrus (July-August). For the May-June and July-August groups combined, estrous, ovulatory and lambing response were higher (P less than .05) during the first induced estrous period (76%, 3.0, 62%) than during the second (33%, 1.9, 43%). In both the first and second induced estrous periods, as interval from PMSG injection to onset of estrus increased, significant declines in ovulation rate, conception rate and ram marking activity were observed, particularly when onset of estrus occurred 72 hr or more after PMSG injection. These results indicate that the reduced lambing responses reported for ewes synchronized during anestrus may be due to increased asynchrony of reproductive events in the ewe, or decreased ram aggressiveness and fertility, or a combination thereof, as the interval from PMSG injection to the onset of estrus increases.

Effect of type of intravaginal progestagen on the outcome of fixed-time artificial insemination

It is now possible to synchronize the cycle of ewes at all times of the year (Gordon, 1975). Conception rates approaching those obtained following natural service have been reported following double (Colas &amp; Brice, 1970; Colas et al. 1973; Barlow, Pryce-Jones &amp; Reed, 1974; Gordon, 1975) or single (Smith, Boland &amp; Gordon, 1978) set-time inseminations. In France, synchronization of ewes' oestrous cycle is based on the use of a Cronolone pessary (Colas, 1975), while field trials conducted in Britain have used the 60 mg Medroxy progesterone acetate (MAP) sponge (Barlow et al. 1974). Robinson et al. (1967) in an evaluation of different progestagen treatments found MAP to be less predictable than Cronolone. The purpose of the present experiment therefore was to evaluate the use of a 30 mg Cronolone or a 60 mg MAP intravaginal treatment when used in conjunction with fixed-time inseminations. In addition, two dose levels of pregnant mare serum gonadotrophin (PMSG) were compared.

Free Amino Acid Content of Ovine Cervicovaginal Mucus

Estrous cycle synchronization of ewes has been accomplished by several methods. Progesterone or a derivative when fed, injected or applied with a vaginal sponge will inhibit estrus and ovulation. When treatment is stopped, estrus and ovulation occur in 1 to 5 days but mating at this estrus has given conception rates lower than those obtained with untreated animals (Hulet, 1966; Robinson and Moore, 1967; Cunningham, Deas and Fitzsimons, 1967). Very little work has been reported on the physiological changes occurring in the reproductive tract during and following treatment with exogenous progestogen. It was found (Perkins and Goode, 1967) that the free amino acid content of oviduct fluid was altered when ewes were synchronized with progesterone. There was a distinct increase in free amino acid concentration of uterine fluids of rabbits treated with progesterone (Gregoire, Gongsakdi and Rakolf, 1961). This research was designed to determine what effects synchronization of ewes with flurogestone acetate3 would have on the concentration of free amino acids in cervicovaginal mucus.