Effect of reproductive methods and GnRH administration on long-term protocol in Santa Ines ewes

Metabolomics analysis of the effect of GnRH on the pregnancy rate of ewes with estrus synchronization scheme based on progesterone

Introduction

Gonadotropin-releasing hormone (GnRH) is widely used in the timed artificial insemination protocol for sheep. However, there remains a debate regarding its impact on pregnancy rates during artificial insemination. This study aims to evaluate the effect of GnRH on the pregnancy rates in Huyang ewes, analyze the pre-implantation metabolite changes caused by GnRH using metabolomics, and elucidate the mechanism effect on pregnancy rates.

Methods

All ewes were administered a vaginal progesterone sponge containing 45 mg of flurogestone acetate for 12 days and received 330 units of equine chorionic gonadotropin (eCG) intramuscularly after sponge removal. The experimental group (n = 69) received an intramuscular treatment of 17 μg GnRH agonist triptorelin 48 h after sponge removal on Day 0, while the control group (n = 41) received 1 mL of sterile saline solution. All ewes underwent a single vaginal insemination 58 h after the withdrawal of the progesterone sponge. The difference in pregnancy rates between the two groups was calculated. Metabolomic analysis was performed on plasma samples collected on Day 7 after the treatment of GnRH agonist.

Results

Gonadotropin-releasing hormone (GnRH) treatment significantly reduced the pregnancy rate in the experimental group compared with the control group (72.2 vs. 82.9%, p < 0.05). Metabolomic analysis indicated that GnRH treatment affected metabolites involved in collagen synthesis and prostaglandin synthesis in the endometrial tissue, which includes a marked decrease in hydroxyproline amino acid content and a significant increase in corticosterone and prostaglandin D2 lipids and unsaturated fatty acids.

Conclusion

In summary, the injection of GnRH agonist Triptorelin 48 h after progesterone sponges removal reduces the pregnancy rate of Huyang ewe following artificial insemination. It also affects the metabolite levels related to endometrial collagen and prostaglandin synthesis, harming embryo implantation.

Effects of injectable and intravaginal progesterone on ewes' reproductive performance at breeding season beginning

Progesterone (P4) is a steroid hormone that has a regulatory role in the female reproductive system. Studies on the effects of injectable progesterone on ewes are scarce, mainly related to their reproductive responses in the breeding season. This study aimed to compare reproductive performance and serum P4 concentration using injectable or intravaginal P4 in ewes. Two hundred and forty and eight Santa Inês x Dorper ewes (BW; 52.67 ± 11.76 kg; mean ± SE), body condition score (BCS; 2.5 ± 0.8; scale of 1-5), were distributed in four treatments: (i) Control: without administration of P4; (ii) CIDR: intravaginal implantation of 330 mg of P4 for 7 days; (iii) 1P4: 15 mg of P4 intramuscular (IM); and (iv) 2P4I: 30 mg of P4 IM. The first 18 days of breeding season were considered the synchronization period. Except for ewes in the control group, all other ewes received 263 μg IM of cloprostenol sodium for lysis of eventual CL at 24 h before the P4 treatment. After the synchronization period, all ewes were kept together with males for extra 28 days in the breeding season. At the beginning of breeding season, 90% of the ewes had serum P4 concentration less than 1 ng/mL. The estrus rate was greater (P < 0.01) in ewes on the CIDR treatment, with similar estrus rate among the other treatments. The P4 implant was able to keep blood P4 concentration greater than 1 ng/mL in ewes that received an implant of P4 during the 7 days. After implant removal, there was a great increase in the estrus manifestation on ewes in the CIDR treatment, leading to an increase in pregnancy rate at the beginning of breeding season. The current study demonstrated that ewes that received an intramuscular injection of 15 or 30 mg of P4 had similar reproductive performance than ewes that did not receive any P4 intramuscular injection. However, when ewes were implanted with P4 (CIDR), these animals had an increase in estrus manifestation, leading to greater pregnancy earlier during the breeding season.

The effect of progesterone length in timed AI in ewes

This study aimed to evaluate the reproductive performance of ewes submitted to timed AI protocol with 7 (D7) or 9 (D9) days of progesterone. A total of 220 crossbred ewes (Doper × Santa Ines) were distributed in the treatments according to body weight (52.67 ± 11.76 kg), body condition score (2.5 ± 0.8; scale of 1-5), and the female category (multiparous, nulliparous and primiparous). Ewes received an intravaginal device of 0.3 g of progesterone (CIDR® Easy breed) on day 0, keeping in ewes for 7 or 9 days, which were the experimental treatments. At the time of P4 withdrawal, ewes received 300 IU of eCG (Novormon®) and 6.70 mg of dinoprost tromethamine (Lutalyse®). Insemination by laparoscopy was performed between 46 and 59 h after device removal, lasting from 1 to 5 min/ewe, which did not differ between protocols. The estrus detection rate was higher in the 9-day protocol compared to the 7-day protocol (82% and 65%, respectively, P = 0.0096). However, the 7-day protocol tended to increase pregnancy rate on the TAI compared to the 9-day protocol (45% and 33%, respectively, P = 0.09). The plasma concentration of progesterone at device removal was higher in the 7-day protocol than in the 9-day protocol (2.35 and 1.22 ng/mL, respectively, P = 0.04). We conclude that reducing the length of the estrus synchronization protocol to 7 days is recommended, which improved the reproductive response in ewes.

Technologies Used in Production Systems for Santa Inês Sheep: A Systematic Review

This study identifies the number of publications that presented technologies used in the production systems of Santa Inês sheep in the last 5 years (2017–2021) carried out in Brazil. Therefore, the objective was to identify where we are in terms of knowledge about technologies in different fields (health, reproduction, animal breeding, behavior and welfare, nutrition and feeding, forage and pasture, carcass and meat quality, and economics and management of livestock systems). After rigorous selection, 114 studies were appointed and classified by knowledge field, and the main approaches within each theme were evaluated, pointing out research gaps. Most technologies have been in northeastern states. However, government agencies should develop public policies to disseminate techniques in rural areas because the production system in this region is still subsistence. This study highlighted the need for works that present management practices and tools that impact the improvement of animal welfare. Agro-industrial by-products have been widely used as an alternative for sheep feeding. However, economic feasibility analyses are recommended with these foodstuffs to substantiate their use as an option to reduce production costs. There is a lack of research allusive to the management of production systems, especially those related to estimates of economic feasibility indicators.

A comparative transcriptome and proteomics study of post-partum ovarian cycle arrest in yaks (Bos grunniens)

Post-partum ovarian cycle arrest is the main factor affecting yak reproductive efficiency. There are few reports regarding the molecular regulatory mechanism of post-partum oestrus at transcriptome and proteome levels in yaks. Our previous studies focussed on the ovaries of yaks with post-partum ovarian cycle arrest and post-partum oestrus yaks. In this study, RNA sequencing transcriptomic study was combined with quantitative proteomic analyses to identify post-partum ovarian cycle-related genes and proteins. Consequently, 1,149 genes and 24 proteins were found to be up- or downregulated during post-partum oestrus. The analysis of differentially regulated genes identified three gene or protein pairs that were synchronously upregulated and no gene or protein pairs that were synchronously downregulated, suggesting that these upregulated genes may regulate the post-partum ovarian cycle. The functional classification of these differentially expressed genes and proteins indicated their connection with the oocyte meiosis, the oestrogen signalling pathway, the progesterone-mediated oocyte maturation and the gonadotrophin-releasing hormone (GnRH) signalling pathway. In this study, a total of six genes and two proteins involved in the oocyte meiosis, the oestrogen signalling pathway, the progesterone-mediated oocyte maturation and the GnRH signalling pathway were identified. The CSNK1A1, M91_09723, M91_11326, M91_21439, M91_19073, SHC2, Atf6b, M91_03062, HSPCA and calmodulin could regulate oestrus, respectively, in the post-partum so as to control the anoestrus status.

The reused progesterone device has the same effect on short or long estrus synchronization protocols in tropical sheep

This study aimed to evaluate the effect of progesterone (P4) device reutilization in long and short protocols for transcervical timed artificial insemination (TAI) in Santa Inês ewes. A total of 275 multiparous lactating ewes were blocked according to body weight (BW, 49.1 ± 7.3 means ± SE), body condition score (BCS, 2.9 ± 0.4; scale of 1-5), and days postpartum (50 ± 8.2 days), and allocated to one of the treatments. The treatments were arranged in a factorial design, in which the factor 1 was the P4 device type (new or a device of 0.3 g of P4 previously used by 11 days), and the factor 2 was the short or long TAI protocol (P4 device remained by 7 or 11 days, respectively). At device removal, all ewes received 300 IU eCG and 6.70 mg of Dinoprost tromethamine. After TAI protocol, ewes remained with ram by 21 days. There was no interaction between factors in any variables. Ewes that received a new P4 device delayed (P = 0.05) to show estrus compared with ewes receiving a previously used P4 device, but it did not affect pregnancy rate. The long protocol tended to increase pregnancy rate compared with short protocol (33% vs. 24%, respectively; P = 0.07). However, the pregnancy rate at the end of reproductive period was similar in both groups (about 84%). Thus, the use of long protocols tended to improve reproductive performance, and the reused P4 device did not affect pregnancy rate.