Effect of a GnRH analogue (Maprelin) on the reproductive performance of gilts and sows

GnRH agonists: Updating fixed-time artificial insemination protocols in sows

Protocols for fixed-time artificial insemination (FTAI) in swine reproduction can help increase genetic improvement and production efficiency. Different gonadotropin-releasing hormone (GnRH) agonists have been developed to gain better control of follicular development, timing, and ovulation quality; therefore, they have been extensively used in FTAI protocols. This literature review resumes the most important characteristics of the physiology of follicular development and ovulation in sows, followed by a discussion about the hormonal alternatives available to induce ovulation (human chorionic gonadotropin, hCG; porcine luteinizing hormone, LH and GnRH agonists). Also, ovulation induction failures with GnRH agonists are described. Finally, current FTAI protocols with GnRH agonists are resumed and discussed. FTAI with GnRH agonists has proven to be an efficient, successful reproductive protocol that can be implemented in pig farms due to better knowledge of an endocrine system that regulates follicular development and ovulation and increased availability of several GnRH agonists that allow more efficient reproductive swine programs.

The effect of fixed-time artificial insemination protocol initiated at different stages of the estrous cycle on follicle development and ovulation in gilts

Hormonal products have been developed for fixed-time artificial insemination (FTAI) to improve the efficiency of swine production. Here, we evaluated the effect of an FTAI protocol initiated during different phases of the estrous cycle on follicle development and ovulation in gilts. A total of 36 gilts were equally divided into three groups designated as the luteal (L), follicular (F), and post-ovulation (O) groups and fed with 20 mg of altrenogest for 18 days, followed by intramuscular injection of 1000 IU PMSG at 42 h after withdrawal of altrenogest, and 100 μg of GnRH after an 80-h interval. The L group had the highest number of follicles 4-6 mm in diameter, as well as corpora hemorrhagica. The mRNA expression of caspase-9 in the L group were significantly lower than those in the O and F groups (P < 0.05), while CYP11A1 and VEGF mRNA expression levels were significantly higher (P < 0.05). Moreover, FSHR mRNA levels were significantly higher in the O group than in the L, F, and control groups (P < 0.05). LHCGR and CYP19A1 mRNA levels were the highest in the F group (P < 0.05). Thus, the changes in the expression of genes associated with follicular development, maturation, and ovulation identified in this study indicated that initiation of the FTAI protocol during the luteal phase induced a better environment for follicle development and ovulation in gilts.

A comparison of the reproductive performance in primiparous sows following two timed artificial insemination protocols

Timed artificial insemination (TAI) is an efficient reproductive technology in batch farrowing production that aids management in pig farms. However, the effect of TAI on the reproduction performance is still controversial. This study aimed to evaluate the effects of two TAI protocols on the reproductive performance of primiparous sows. A total of 332 weaned sows were randomly allocated into three treatments. Sows assigned to Control (n = 110) were untreated and inseminated on each day in oestrus after weaning. Sows assigned to eG-TAI (n = 112) received equine chorionic gonadotropin (eCG) 24 h after weaning and gonadotropin-releasing hormone (Gonadorelin: GnRH) at oestrus, and were inseminated at 8 and 32 h later if oestrus at 0800, or 16 and 40 h later if oestrus at 1600. Sows assigned to 2e-TAI (n = 110) received eCG and GnRH 24 h and 96 h after weaning, respectively, and were inseminated 16 and 40 h after GnRH administration. Sows showing oestrus at GnRH administration or 64 h after were inseminated immediately, for a total of three inseminations. Ultrasonographic evaluations were performed to determine the follicular diameter and time of ovulation. Most sows in the 2e-TAI and eG-TAI groups ovulated 0-48 h after the GnRH injection. Our results indicated that oestrus rate within seven days after weaning in the experimental groups was higher, and weaning-to-oestrus interval was shorter than in the control group (99.3 h vs 113.5 h, P < 0.05). The breeding and farrowing rates in the experimental groups were significantly higher than in the control group (P < 0.05), while the numbers of total born, live-born and stillborn were not different among the three groups (Control: 12.7, 11.6 and 1.1; 2e-TAI: 12.4, 11.3 and 1.0; eG-TAI: 12.0, 11.4 and 0.4, respectively). These results indicated that TAI could ensure a high farrowing rate in primiparous sows under batch farrowing management.

Equine chorionic gonadotropin pretreatment 15 days before fixed-time artificial insemination improves the reproductive performance of replacement gilts

Fixed-time artificial insemination (FTAI) technology uses exogenous reproductive hormones to regulate the sexual cycle and ovulation of sows without oestrus identification, which improves the sow breeding utilisation rate, reduces the number of non-productive days, and elevates the efficiency of pig farm management. In this study, we aimed to optimise FTAI procedures. Healthy 190-day-old and about 90 kg Large White × Landrace crossing breed replacement gilts (n = 166) which were of unknown reproductive status were randomly selected and divided into three groups: a control group (n = 62), an eCG-15D group in which the gilts were pretreated with equine chorionic gonadotropin (eCG) injection 15 days before starting FTAI (n = 50), and an eCG-20D group pretreated with eCG injection 20 days before starting FTAI (n = 54). All three groups were then subjected to the same conventional FTAI procedure. Pigs were orally administered Altrenogest (ALT, 20 mg per pig per day) for 18 days and then 42 h after ALT feeding was stopped, they were injected with 1 000 IU eCG followed by 100 μg GnRH 80 h later. The gilts were inseminated for the first time 24 h after gonadotropin-releasing hormone (GnRH) injection and then again 16 h later. After 42 h of ALT feeding, gilts in the eCG-15D group displayed a higher follicular diameter until artificial insemination (AI) than those from the other groups (P < 0.05). In addition, the ovulation times were the most synchronised in the eCG-15D group, with 100% of the gilts ovulating before the second AI on day 25 of FTAI. Furthermore, the gilts in the eCG-15D group achieved the highest pregnancy rate (92%), farrowing rate (90%), total pigs born (11.59), and pigs born alive (11.18). Together, the findings of this study demonstrate that reproductive performance can be optimised by pretreating gilts with eCG 15 days before conventional FTAI.

Single Fixed-Time Post-Cervical Insemination in Gilts with Buserelin

Current protocols for gilts recommend the deposit of multiple semen doses in the cervix each 12-24 h after estrus detection. Our objectives were: (1) to determine the effect of buserelin and a single fixed-time artificial insemination using the new post-cervical artificial insemination technique (FTAI-PCAI) on reproductive and productive performance in gilts, and (2) to compare this protocol with conventional estrus detection and double PCAI without hormonal induction. In the control group (C; n = 240), gilts were inseminated twice (8 and 12 h from estrus onset). Gilts in the treatment group (T; n = 226) received buserelin (10 μg, intramuscular) 120 h after altrenogest treatment (18 d) and one single PCAI 30-33 h after buserelin administration. The groups did not differ in reproductive and production performance (p > 0.05). The T group showed greater piglet birth weight and shorter estrus duration (p < 0.001). Delivery batch length differed significantly depending on the season (p < 0.05); the shortest length corresponded to autumn. Both groups only differed significantly in spring (p = 0.018), with a shorter length in the T group. This new FTAI-PCAI protocol with buserelin is recommended in gilts, helping with optimization of genetic diffusion, boars, and semen doses.

Improving ovulation in gilts using anti-inhibin serum treatment combined with fixed-time artificial insemination

For successful batch farrowing, porcine oestrus and ovulation must be synchronized using fixed-time artificial insemination (FTAI). However, exogenous gonadotropins, which are currently used in FTAI, negatively affect gilt ovulation. Here, we aimed to improve sexually mature gilt superovulation efficiency using passive immunization against inhibin during FTAI. Altrenogest-treated gilts were challenged with 10 ml anti-inhibin serum (AIS group, n = 6), 1,000 IU pregnant mare serum gonadotropin (PMSG group, n = 6), or 10 ml goat serum (control group, n = 6). Gilts in the AIS and PMSG groups were inseminated according to the FTAI protocol, and gilts in the control group were inseminated during natural oestrus. When PMSG was replaced by AIS during FTAI of gilts, ovulation rate and embryos recovered were significantly greater in the AIS group as compared to the other two groups (p < .05). Especially the average number of 6-8-cell embryos in the AIS group was significantly higher than that in the PMSG group (p < .01). Moreover, the blastocyst number in the AIS group was significantly higher than that in the PMSG group and the control group (p < .05). But there was no significant difference in the blastocyst number between the PMSG group and the control group (p > .05). Besides, plasma levels of estradiol-β (E2) and progesterone (P4) were significantly greater in the AIS group as compared to the other two groups on Day 23 and D 27, respectively (p < .01). In summary, we devised an improved high-yield FTAI protocol for sexually mature gilts using AIS; this protocol had a greater superovulation efficiency than the FTAI using PMSG.

Effects of intravaginal devices containing different dosages of medroxyprogesterone acetate for the control of the estrous cycle in gilts

This aim of this study was to investigate the effectiveness of intravaginal devices (IVDs), containing medroxyprogesterone acetate (MPA), for controlling the estrous cycle in pubertal gilts. Gilts were assigned to four treatments: Control (no IVD); IVD containing 100 (IVD100), 200 (IVD200) or 400 mg (IVD400) of MPA. The IVDs were inserted on day 12 of the estrous cycle and maintained intra-vaginally for 14 days. The percentage of gilts in estrus, interval between IVD removal and estrous onset, adjusted farrowing rate (AFR), total number of piglets born (TPB), follicle size and serum progesterone (P4) were recorded. None of the gilts expressed estrus during the IVD treatment period. All gilts of the control group expressed estrus (15/15; 100%) which was greater (P =  0.03) than all IVD-treated gilts (33/44; 75%); however, there were no treatment differences (P =  0.09). The interval between IVD removal and estrous onset was shorter for IVD100 (3.8 ± 0.6 d) compared to IVD400 (5.3 ± 0.6 d; P = 0.05). The IVD400-treated gilts had smaller follicles than the IVD100-treated gilts (P =  0.05). The P4 concentrations were similar among treated groups (P =  0.99). The AFR did not differ among treatment groups (P = 0.37); however, the control group had a greater TPB than the other treatment groups (P =  0.04). The gilts treated with IVDs had longer interval to estrous expression. The most effective dosage was 400 mg of MPA, considering both the minimal follicular growth during the IVD treatment period and the lesser numbers of persistent follicles.

Progesterone and pregnant mare serum gonadotropin improve the reproductive capacity of long-term non-oestrus replacement gilts

Context It is a common problem that replacement gilts exhibit delayed oestrus and non-oestrus in pig production. Aims This study explored the use of progesterone and pregnant mare serum gonadotropin (PMSG) to promote oestrus and to restore the reproductive capacity of sows. Methods A total of 90 long-term non-oestrus replacement gilts were randomly divided into three groups. Group A consisted of 30 sows that were normally fed for 20 days, followed by injections of 1000 IU of PMSG on the morning of the 21st day and 100 μg of gonadotropin-releasing hormone on the 24th day. Group B consisted of 30 sows that were continuously fed with altrenogest (20 mg/head.day) for 18 days, followed by injections of 1000 IU of PMSG on the morning of the 21st day and 100 μg of gonadotropin-releasing hormone on the 24th day. Group C (control group) consisted of 30 sows that were normally fed for 20 days, followed by injections of 3 mL of physiological saline on the morning of the 21st day and 3 mL of saline on the 24th day. Oestrus identification was performed in all three groups, and sows underwent artificial insemination after the injection of gonadotropin-releasing hormone or saline. Key results We found that the follicles of long-term non-oestrus replacement gilts were not developed, and follicle diameters were &lt;4 mm. The oestrus rate and pregnancy rate of the sows in Group B were significantly lower than those in Group A (30% vs 66.7% and 66.7% vs 90%) respectively. There was no difference in the litter size between Group A and Group B (11.2 vs 11.5). The sows in Group C exhibited no oestrus and no pregnancy. After treatment with progesterone and PMSG, the follicle diameters of sows in oestrus were significantly greater than those of sows in non-oestrus, and the levels of oestradiol, luteinising hormone and follicle-stimulating hormone were significantly higher than those of sows in non-oestrus. Conclusions This study showed that progesterone and PMSG treatment can alter the reproductive hormone levels and follicle diameters in long-term non-oestrus replacement gilts, promote oestrus and restore reproductive capacity in sows. Implications This study provides a method for the use of hormone-treated gilts to maximise the reproductive potential of gilts.

Effect of a GnRH analogue (peforelin) on the litter performance of gilts and sows

Background

Maintaining optimal reproductive and litter performance is essential for meeting economic targets in commercial pig production. Treatment with exogenous gonadotropins in sows after weaning or in gilts after altrenogest treatment has been used to stimulate follicular development leading to more piglets born and eventually higher birth weights. The effect of peforelin on litter performance was investigated in 212 gilts, primi- and pluriparous sows in three herds. Animals were randomly allocated to three treatments 24 h after weaning: peforelin (P group), eCG (E group), and physiological saline solution (C group). Numbers of total, liveborn and stillborn piglets and mortality rate during lactation were recorded. Birth weights and coefficient of variation in weights within litter were assessed. All parameters were compared among treatments.

Results

Over all parities, no difference was found among treatments in litter size nor mortality rate, but birth weights were significantly lower in the E group. Stillbirth numbers in pluriparous sows were 2.2, 0.9 and 1.4 for P, E and C groups, respectively (p = 0.04). Piglets in the P group had significantly higher live born birth weights in gilts, compared to the E group (1.36, 1.26, 1.32 kg (p < 0.02) for P, E and C group, respectively). No significant differences were found for the other investigated parameters.

Conclusions

Peforelin treatment showed no improvement of litter performance compared to no treatment.

Advances in Breeding Management and Use of Ovulation Induction for Fixed-time AI

The objective of the breeding herd is the predictable and consistent production of high quality pigs. To achieve this objective, an appropriate number of females need to be mated in each breeding week and they should maintain their pregnancy and deliver large litters. Many factors can impact achievement of optimal sow productivity, particularly breeding management. Most matings will involve artificial insemination (AI), and successful AI requires deposition into the cervix (or beyond) of sufficient viable high quality sperm at an appropriate time relative to ovulation. This is facilitated by improved knowledge of the sow's ovarian function prior to and during her oestrous period. Realization of the importance of establishing an adequate sperm reservoir in the oviduct at an appropriate time relative to ovulation has led to advances in the management of AI. The future of AI will likely involve insemination of single doses of high genetic merit semen, potentially having a reduced sperm concentration which is made possible by knowledge of the effect of site of sperm deposition on sow fertility. In particular, knowledge of when a sow is likely to ovulate during a natural or induced oestrous period will prove invaluable in the maintenance of herd productivity. This review will examine options for breeding management, including the control of oestrus and ovulation, on sow herd reproductive performance.

An evaluation of gonadotropin-releasing hormone analogue administered to gilts and sows on subsequent reproductive performance and piglet birth weight

Background

The present study investigated the effect of peforelin (Maprelin®), a gonadotropin-releasing hormone (GnRH) analogue, administration in gilts, primiparous and pluriparous sows in a high productive farm on sow reproductive performance and piglet quality at birth.

Methods

In a 400 sow herd, gilts, primiparous and pluriparous sows were randomly allocated to 2 groups: peforelin treated (peforelin = P-group) or no treatment (control = C-group). Animals were injected 48 h after the last altrenogest treatment (gilts) or 24 h post weaning (sows). Weaning-to-estrus interval (WEI), estrus rate (ER), farrowing efficiency index (FEI), farrowing rate (FR), number of total (TBP), live (LBP) and stillborn piglets (SBP), mummies (MM) and live piglet index (LPI) were assessed and compared between treatment groups. To assess piglet quality at birth, 6033 piglets from 426 litters were weighed individually within 24 h after birth (BW; birth weight).

Results

No significant difference between treatment groups could be observed for WEI, TBP, LBP, SBP and MM. The ER was significantly (P = 0.0119) higher (93.2 %) in the P-group as compared to the C-group (87.2 %). Peforelin treatment did not affect farrowing rate. Both FEI and LPI were significantly (P = 0.0078) better in the P-group as compared to the C-group. Overall, no effect of peforelin treatment on piglet birth weight could be observed, although specific subcategories (1st parity and older (5+ parity) sows) did have a significant impact of treatment on birth weight. During late summer (August-September) all treated gilts and sows took advantage from peforelin treatment with a significant improvement of piglet birth weight.

Conclusion

Peforelin treatment had a significant impact on ER, FEI and LPI. Moreover, piglet birth weight improved for specific sow subcategories (1st parity and older sows) and for all gilts and sows during the late summer infertility period.

Recent advancements in the hormonal stimulation of ovulation in swine

Induction of ovulation for controlled breeding is available for use around the world, and conditions for practical application appear promising. Many of the hormones available, such as human chorionic gonadotropin (hCG), gonadotropin-releasing hormone (GnRH) and its analogs, as well as porcine luteinizing hormone (pLH), have been shown to be effective for advancing or synchronizing ovulation in gilts and weaned sows. Each of the hormones has unique attributes with respect to the physiology of its actions, how it is administered, its efficacy, and approval for use. The timing for induction of ovulation during the follicle phase is critical as follicle maturity changes over time, and the success of the response is determined by the stage of follicle development. Female fertility is also a primary factor affecting the success of ovulation induction and fixed time insemination protocols. Approximately 80%-90% of female pigs will develop mature follicles following weaning in sows and synchronization of estrus in gilts. However, those gilts and sows with follicles that are less developed and mature, or those that develop with abnormalities, will not respond to an ovulatory surge of LH. To address this problem, some protocols induce follicle development in all females, which can improve the overall reliability of the ovulation response. Control of ovulation is practical for use with fixed time artificial insemination and should prove highly advantageous for low-dose and single-service artificial insemination and for use with frozen-thawed and sex-sorted sperm.