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

Estrous, ovulation and reproductive responses of ewes synchronized with a long interval prostaglandin-based protocol for timed AI

The aim was to characterize and assess the reproductive performance of a long interval prostaglandin (PG)-based protocol for timed AI (TAI) at different times. During breeding season three experiments were done involving 622 Merino ewes, 11 rams, and five androgenized wethers per 100 ewes. All ewes were estrus synchronized with two PG injections 15-day apart (PG15): Day -15 and 0 (Hour 0). Estrous distribution respect to Hour 0, estrous response and synchrony after Hour 0, and interval from Hour 0 to estrus detection (PG-estrus) was evaluated (Experiment I; n = 105 ewes). Interval from estrus detection to ovulation (estrus-ovulation) and from Hour 0 to ovulation (PG-ovulation) was determined (Experiment II; n = 12 ewes). Visual-physical score of cervical mucus at TAI, non-return to service to Day 23 (NRR23), fertility, prolificacy, and fecundity to Day 60 in four cervical fresh semen TAI groups was evaluated (Experiment III; n = 505 ewes; 107 nulliparous-398 multiparous). Three groups with single service at 56 (Control), 44 or 68, and one with double service at 44 and 68 ± 1.5 h after Hour 0 (PG15-56, PG15-44, PG15-68, and PG15-44/68 groups, respectively) were tested. Ninety-eight-point one percent of the ewes showed estrus from Hour -48 up to 84 respects to Hour 0. Twenty percent of them showed estrus from Hour -48 up to 0, and 78.1 % from Hour 12 up to 84 (Experiment I). The largest proportion of ewes in estrus was observed between Hour 36 and 60 (80.5 %). PG-estrus interval was 54.1 ± 10 h (means ± SD). Estrus-ovulation interval was 32.4 ± 5.8 h, and PG-ovulation interval was 77.0 ± 16.6 h (Experiment II). Ewe parity did not affect any of the reproductive variables (P > 0.05; Experiment III). There were no significant differences (P > 0.05) between Control and different groups in mucus score (2.18 ± 0.08, 2.02 ± 0.07, 2.14 ± 0.09, 2.25 ± 0.10), NRR23 (76.0, 71.9, 78.6, 79.4 %) or fertility (66.4, 64.1, 66.7, 73.8 %; PG15-56, PG15-44, PG15-68 or PG15-44/68 groups, respectively). Prolificacy in PG15-44 group was lower (1.07 ± 0.03; P < 0.05) than other groups (1.27 ± 0.05, 1.23 ± 0.05, 1.20 ± 0.04), and fecundity than PG15-44/68 group (0.84, 0.69, 0.82, 0.89), without differences among other groups (PG15-56, PG15-44, PG15-68 or PG15-44/68 groups, respectively). We concluded that any time between 56 and 68 h after PG15 protocol could be used to perform cervical TAI using fresh semen, without benefits of a double TAI service at 44 and 68 h.

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.

Treatments with intravaginal sponges for estrous synchronization in ewes: length of the treatment, amount of medroxyprogesterone, and administration of a long-acting progesterone

We evaluated if alternative treatments achieve at least similar results as traditional long treatments with intravaginal sponges (IVS) in three experiments considering (1) the use of 6-day treatments associated or not with the administration of PGF2alpha at IVS insertion; (2) a reduction of 50% MAP content in short-term or traditional treatments, with or without change of the IVS 6 days after its insertion; and (3) the substitution of IVS for long-time acting injected progesterone associated with the administration of a PGF2alpha. More ewes came into estrus with long than short IVS treatments, independently of the MAP IVS content. Fewer ewes came into estrus if the IVS containing 30 mg was replaced 6 days after its insertion. The length of the treatment did not affect the conception rate, but the pregnancy rate was greater in 12 than 6 days treatments. The administration of long-acting progesterone did not prevent the lower conception rate associated with the use of PGF2alpha and was less effective to synchronize estrus, but the conception rate did not differ from that of 12d IVS treatments. Overall, MAP content could be decreased without affecting the estrous rate; thereafter, the MAP IVS content should be decreased in the commercial devices. Although pregnancy rate was lower using long-acting injected progesterone than with IVS, as the conception rate did not differ, it is interesting to study deeper the use of this treatment, especially if preparations of progesterone with a longer half-life are developed. However considering all the results, the traditional long IVS treatment still provided the best result.

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.

Long interval prostaglandin-based treatment regimens do not affect ovulatory or prolificacy rates of multiparous ewes after cervical fixed timed AI

To evaluate effects of a longer, than conventional, interval between time of prostaglandin F_2α (PG)-based administrations in a PG-based treatment regimen for fixed timed AI (FTAI) on ovulation rate (OR), non-estrous return rate on Day 21 subsequent to the time of AI (NRR21), as well as conception, prolificacy and fecundity rates, ewes were assigned to two groups. Ewes of treatment group (PG15) were estrous-synchronized using two PG doses 15 days apart and FTAI was conducted at 56 h after the second PG administration (Day 0). Ewes of the Control group (SE) had imposed a pre-estrous synchrony treatment regimen with two PG doses 7 days apart and AI was conducted after detection of spontaneous estrus from 17 to 19 days after the second PG administration (Day 0). Ovulation rate on Day 8, NRR21, conception, prolificacy and fecundity rates on Day 60 were evaluated. There were no differences (P > 0.05) between ewes of the PG15 and SE groups in OR (1.47 ± 0.50 and 1.54 ± 0.50, respectively) or prolificacy (1.42 ± 0.80 and 1.33 ± 0.62, respectively), however, there were lesser values (P< 0.05) in the PG15 than SE group for NRR21 (65.2% and 91.3%, respectively), conception (59.8% and 91.3%, respectively) and fecundity (84.8% and 120%, respectively). The longer interval with the PG-based treatment regimen does not affect OR and prolificacy, but there is a lesser NRR21, conception and fecundity rate in comparison to ewes of the Control group.

Technical recommendations for artificial insemination in sheep

Artificial insemination (AI) was the first important biotechnology applied to improve the genetics of farm animals. It allows the rapid and massive diffusion of desirable characteristics of males with high productive potential. We describe the different types of estrus induction and synchronization techniques and the use of the AI with fresh, chilled or frozen semen. Through the adequacy of the protocols of estrus synchronization and AI to the different production systems, the efficient use of reproductive techniques is possible, reaching acceptable pregnancy rates. Summary of reproductive results obtained using cervical and laparoscopic AI are presented.

Short-term dietary protein supplementation improves reproductive performance of estrous-synchronized ewes when there are long intervals of prostaglandin or progesterone-based treatments for timed AI

To evaluate the reproductive effects of a short-term dietary protein supplementation (Days -10 to -3) before timed AI (TAI = Day 0), 471 Merino ewes grazing native pastures were estrous-synchronized when there were either long intervals between prostaglandin administrations (two prostaglandin injections 15 or 16 d apart; PG15 and PG16, respectively) or with a progesterone-eCG (P4-eCG) protocol, resulting in a 3 × 2 experimental design. Ovulation rate on Day 8 (OR), non-estrous-return to Day 21 (NRR21), and fertility, prolificacy and fecundity on Day 70 were evaluated. The interaction between estrous synchronization protocol and supplementation was not significant for any of these variables (P > 0.05). Supplementation increased OR, prolificacy and fecundity (+0.14, +0.15 and +0.14, respectively, P < 0.01), but did not affect NRR21 or fertility of ewes (+6.2% and +6.7% respectively, P > 0.05). Ewes treated using the PG15 and PG16 protocols had a lesser OR (-0.27), prolificacy (-0.22) and fecundity (-0.20) than ewes treated using P4-eCG protocol (P < 0.01 for each), and similar NRR21 and fertility (-5.4% and -7.9% respectively, P > 0.05 for both variables), without significant differences between the PG15 and PG16 groups. In conclusion, a short-term dietary protein supplementation before TAI improved OR, prolificacy and fecundity of ewes which were estrous-synchronized by imposing long interval PG (15 or 16 d apart) or P4-eCG-based protocols. There was a greater OR, prolificacy and fecundity when there was use of the P4-eCG compared to long interval PG-based protocols. Estrous-non-return rate after AI and fertility as a result TAI were not affected by either the supplementation or the estrous synchronization protocols used.

Short term protein supplementation during a long interval prostaglandin-based protocol for timed AI in sheep

The aim of this study was to evaluate the reproductive impact of a short-term protein supplementation on a long interval prostaglandin-based protocol (two PG injections 15 d apart; PG15) for timed artificial insemination in sheep. During the breeding season, 437 multiparous Merino ewes grazing native pastures (forage allowance of 6 kg of dry matter/100 kg of live weight; crude protein: 10.8%, metabolic energy: 2.1 Mcal/kg of dry matter) were selected. Ewes were allocated, according to body condition score (3.2 ± 0.2) and body weight (40.6 ± 4.9 kg, mean ± SD), to a 2 × 2 factorial design: type of estrus -spontaneous estrus (SE) or induced with PG15 (PG15)-, and supplementation (yes or no) before insemination (+FF; soybean meal at Days -10 to -3; crude protein: 51.9%, metabolic energy: 2.8 Mcal/kg of dry matter; average consumption 0.9% live weight/ewe/day of dry matter). All ewes were cervically artificial inseminated (Day -2 to -3 in SE ewes at estrus detection; Day 0 = timed artificial insemination in PG15 ewes). Ovulation rate on Day 7, non-return to service on Day 23, conception, fertility, prolificacy and fecundity on Day 60 were evaluated. Ovulation rate (1.17 ± 0.40 vs. 1.06 ± 0.25), non-return to service at Day 23 (81.7 vs. 64.2%), conception (78.8 vs. 61.5%), fertility (75.2 vs. 61.5%) and fecundity (0.77 vs. 0.62) were higher in ewes from SE than PG15 group (P < 0.05). However, no differences were observed in prolificacy (1.02 ± 0.16 vs. 1.01 ± 0,12) between groups (P > 0.05). Protein supplementation increased ovulation rate (1.30 ± 0.45 vs. 1.17 ± 0.40), prolificacy (1.18 ± 0.39 vs. 1.02 ± 0.16) and fecundity (0.94 vs. 0.77%; P < 0.05), but not non-return to service on Day 23 (83.8 vs. 81.7%), conception (82.9 vs. 78.8%) or fertility (79.1 vs. 75.2%; P > 0.05) in SE group. The supplement feed to PG15 ewes increased ovulation rate (1.35 ± 0.45 vs. 1.06 ± 0.25), prolificacy (1.25 ± 0.43 vs. 1.01 ± 0.12) and fecundity (0.79 vs. 0.62%; P < 0.05) to levels comparable to SE + FF ewes (P > 0.05). The magnitude of the increase in ovulation rate in PG15 was greater than in the SE group (27 vs. 11%; P < 0.05). However, non-return to service on Day 23 (65.1 vs. 64.2%), conception (63.3 vs 61.5%), and fertility rate (63.3 vs. 61.5%; P < 0.05) remained similar in PG15 supplemented or not supplemented ewes. In conclusion, a short-term protein supplementation before cervical time artificial insemination improved the reproductive performance of ewes synchronized with the PG15 protocol to levels comparable to the SE group.