Time of ovulation and pregnancy outcomes obtained with the prostaglandin-based protocol Synchrovine for FTAI in sheep

Comparison of Five Protocols of Estrous Synchronization on Reproductive Performance of Hu Sheep

The purpose of this study is to compare five protocols of estrous synchronization for Hu ewes to obtain the most effective and economical protocol, to apply the advantageous scheme in large-scale sheep farming. Healthy multiparous Hu ewes (n = 150) were randomly divided into five groups, and all ewes were administered fluorogestone acetate (FGA, 45 mg) vaginal sponge. The sponges of the first three groups (Groups I, II, and III) were removed on the 11th day, and 0.1 mg of PGF_2α was injected intramuscularly on the ninth day. Group I received 6 μg of gonadotropin-releasing hormone (GnRH) by intramuscular injection at 36th h after withdrawal of the sponge. Group II was injected 330 IU of pregnant mare serum gonadotropin (PMSG) on the ninth day. The combination of 6 μg of GnRH and 330 IU of PMSG was treated in Group III at the same time as Group I and Group II. The sponges of the latter two groups (Groups IV and V) were removed on the 13th day, and 330 IU of PMSG was injected intramuscularly simultaneously. PGF_2α (0.1 mg) was administered on the 12th day in Group IV. All ewes were detected for estrus at 24, 36, 48, 60, and 72 h after the sponge removal. The loss of sponge and vaginitis was recorded when the sponge was withdrawn. Cervical artificial insemination (AI) was performed with fresh semen of Dorper rams diluted with skimmed milk. After 30 days of insemination, the conception was detected with a veterinary B-ultrasound scanner. The lambing status of all ewes and the cost of drugs for estrous synchronization in each group were recorded. The results showed the following: (1) on the whole, the average percentage of estrous ewes in the period of 24–36 h and 36–48 h after removal was significantly higher than other three periods and that of the period of 60–72 h was significantly lower than the first three periods after removal; (2) there was no significant difference in percentages of estrous ewes in any of the five time periods, sponge loss rate, vaginitis rate, total percentage of estrous ewes, conception rate, single lambing rate, twinning rate, and multiple lambing rate of ewes among five protocols; (3) total percentage of estrous ewes and conception rate were more than or equal to 80% in the Groups II and III, and the twinning lamb rate of the Group II protocol was 70%; (4) there was no difference in lambing rate of ewes among Groups II, III, IV, and V; (5) the Group III had the highest drug cost of 22.5 CNY. In conclusion, considering the lambing rate, twinning lamb rate, and drug cost for estrous synchronization, Group II was the most advisable for application and promotion in large-scale sheep farms among these five protocols of estrus synchronization.

Approaches of estrous synchronization in sheep: developments during the last two decades: a review

The objective of the current review was to summarize the protocols used for estrous synchronization in ewes during the last two decades. Progesterone (P4) is a major hormone used in most protocols. P4 in the form of a controlled internal drug releasing (CIDR) device, medroxyprogesterone acetate (MAP), and fluorogestone acetates (FGA) has been used for estrous synchronization. Also, gonadotropins such as equine chorionic gonadotropin (eCG) and gonadotropin-releasing hormone (GnRH) are often administered at the end of P4-based protocols to improve fertility. Moreover, the administration of prostaglandins (PG) and ram effects have been used for estrus induction and synchronization of ewes. The findings of previous studies indicate that the outcome of administering various synthetics P4 analogues (CIDR, MAP, and FGA) in ewes is comparable in terms of estrous synchronization/induction. The supplementation of P4-based protocols with eCG, however, improves the estrus response and pregnancy rate during breeding and non-breeding season. On the other hand, PG is effective for successful estrous synchronization during the breeding season only. Often, two injections of PG are administered either 11 or 14 days apart along with P4-based protocols to lyse ovine corpus luteum (CL) when it is receptive to PG i.e., 3 days post-ovulation. Alternatively, the "ram effect" has been shown to improve the efficacy of P4-based protocols and can be used as an alternative to eCG in ewes. The current review describes the methods of synchronization and their outcomes during breeding and a non-breeding season in ewes.

Seventy years of progestagen treatments for management of the sheep oestrous cycle: where we are and where we should go

Management of the ovine oestrous cycle is mainly based on the use of exogenous hormones to mimic or enhance (progesterone and its analogues) or manipulate (prostaglandin F2α and its analogues) the activity of the corpus luteum, combined with the application of other hormones mimicking the pituitary secretion of gonadotrophins (e.g. equine chorionic gonadotrophin). These protocols have been applied without major change for decades but, now, there are two reasons to reconsider them: (1) our greatly improved knowledge of the dynamics of ovarian physiology, following the application of transrectal ultrasonography, indicates that modification of the protocols may improve fertility yields and (2) increasing concerns about animal health and welfare, food safety and the environmental impact of the treatments, as evidenced by public opinion and therefore market forces. Here, we offer an overview of these issues, introduce an updated protocol and suggest ways for future improvements to the protocols.

Addition of eCG to a 14 d prostaglandin treatment regimen in sheep FTAI programs

In the present study, there was evaluation of the alternative of adding eCG as part of a long-interval prostaglandin-F_2α (PG) treatment on the reproductive efficiency of Merino sheep during the breeding season. A total of 210 ewes and 182 ewe lambs were randomly assigned to three experimental groups to induce the timing of estrus among ewes in a: Long-interval PG, group being synchronized using two doses of PG 14 days apart; Long-interval PG + eCG group being synchronized using the same treatment regimen as Group PG with the addition of 200 IU eCG to the regimen, administered concomitantly with the second PG administration; and MAP + eCG group being synchronized with intravaginal progestin sponges for 14 days plus 200 IU eCG, administered at the time of sponge removal. The percentage pregnancy rate in ewes of the MAP + eCG group was greater than the ewes of the Long-interval PG and Long-interval PG + eCG groups (76.4 % compared with 52.0 % and 62.5 %, respectively; P < 0.05). The prolificacy rate was greater in the ewes of the Long-interval PG+eCG group compared with the other groups (114 % compared with 100 % and 103 %, respectively; P < 0.05). When considering the fecundity rate, ewes of the Long-interval PG+eCG and MAP+eCG groups had greater values than ewes of the Long-interval PG group (71.2 % and 78.8 % compared with 52.0 %, respectively; P < 0.05). The Long-interval PG+eCG is an alternative to the conventional progestin sponge plus eCG treatment regimen with there being a greater fecundity rate when this regimen is used compared with the Long-term PG and similar to MAP-eCG treatment regimens.

Effects of d-cloprostenol administrations with 7.5 and 11.5-day intervals between administrations on pregnancy rates after artificial insemination in estrous cyclic dairy goats

This study was conducted to evaluate effects of two administrations of d-cloprostenol at different intervals to synchronize the time of estrus and ovulation among estrous cyclic goats. In Experiment 1, 32 does were treated with 30 μg d-cloprostenol at 7.5 (T7.5, n = 16) or 11.5-day (T11.5, n = 16) intervals. In Experiment 2, the same treatments were administered and there was AI of the does (T7.5, n = 40 and T11.5, n = 38). In Experiment 1, ultrasonic assessments of ovaries were conducted at the time of the second administration of d-cloprostenol, every 12 h until detection of ovulation, and 7 days after estrous onset to detect the corpora lutea, as well as for pregnancy diagnosis 40 days after AI. In Experiment 1, the estrous response (90.6%, 29/32) was similar (P > 0.05) in both groups. Diameter of the largest follicle at the time of administration of the second dose was larger (P = 0.01) in the T7.5 than T11.5 group (7.0 compared with 5.7 mm), while the values for ovarian variables were similar (P > 0.05). In Experiment 2, the greatest (P < 0.001) synchrony in timing of initiation of estrus in does (T7.5 = 83.3% and T11.5 = 50.0%) occurred after the second day (36-48 h). The pregnancy rate tended (P = 0.0836) to be greater for does in the T7.5 (71.4%, 40/56) than T11.5 (55.6%, 30/54) group. With use of both protocols, there were acceptable estrous synchronization and pregnancy rates in estrous cyclic dairy goats.

Long interval prostaglandin as an alternative to progesterone-eCG based protocols for timed AI in sheep

To compare the reproductive performance after TAI in ewes synchronized with mid (12 or 13) or long (14-16 d) interval prostaglandin (PG) or progesterone plus eCG (P4-eCG) based protocols, 440 multiparous Corriedale ewes were synchronized with two PG injections administered 12-16 d apart (PG12, PG13, PG14, PG15 and PG16 respectively), or P4-eCG (MAP sponges 14 d and eCG). Cervical TAI (Day 0) was performed with fresh semen. It was evaluated the ovulated ewes (OE, %) and the ovulation rate (OR) on Day 8 by trans-rectal ultrasonography, the rate of non-return to service between Days 13 and 21 by painted rams, and the pregnancy rate, prolificacy and fecundity on Day 60 by trans-abdominal ultrasonography. No significant differences were found in OE among groups (P>0.05), but P4-eCG achieved higher OR (P<0.05) compared to PG protocols, without differences among them (P>0.05). Similar NRR-21, pregnancy and fecundity were observed among PG15 (64.3, 62.9 and 84.3), PG16 (59.7, 59.7 and 77.8) and P4-eCG (70.3, 66.2 and 95.9), but higher compared to PG12 (42.5, 39.7 and 52.1) and PG13 group (44.0, 40.0 and 48.0, respectively; P<0.05). PG14 achieved intermediate results compared to other groups. No differences were found in prolificacy among groups (P>0.05), except PG13 that was lower compared to P4-eCG (P<0.05). In conclusion, long interval between PG injections (15 or 16 d) determined better reproductive outcome that mid interval (12 or 13 d), equating the P4-eCG based protocol after cervical TAI with fresh semen during the breeding season in sheep.